gcc

GCC(1)                                 GNU                                GCC(1)



NAME
       gcc - GNU project C and C++ compiler

SYNOPSIS
       gcc [-c|-S|-E] [-std=standard]
           [-g] [-pg] [-Olevel]
           [-Wwarn...] [-Wpedantic]
           [-Idir...] [-Ldir...]
           [-Dmacro[=defn]...] [-Umacro]
           [-foption...] [-mmachine-option...]
           [-o outfile] [@file] infile...

       Only the most useful options are listed here; see below for the
       remainder.  g++ accepts mostly the same options as gcc.

DESCRIPTION
       When you invoke GCC, it normally does preprocessing, compilation,
       assembly and linking.  The "overall options" allow you to stop this
       process at an intermediate stage.  For example, the -c option says not to
       run the linker.  Then the output consists of object files output by the
       assembler.

       Other options are passed on to one or more stages of processing.  Some
       options control the preprocessor and others the compiler itself.  Yet
       other options control the assembler and linker; most of these are not
       documented here, since you rarely need to use any of them.

       Most of the command-line options that you can use with GCC are useful for
       C programs; when an option is only useful with another language (usually
       C++), the explanation says so explicitly.  If the description for a
       particular option does not mention a source language, you can use that
       option with all supported languages.

       The usual way to run GCC is to run the executable called gcc, or
       machine-gcc when cross-compiling, or machine-gcc-version to run a
       specific version of GCC.  When you compile C++ programs, you should
       invoke GCC as g++ instead.

       The gcc program accepts options and file names as operands.  Many options
       have multi-letter names; therefore multiple single-letter options may not
       be grouped: -dv is very different from -d -v.

       You can mix options and other arguments.  For the most part, the order
       you use doesn't matter.  Order does matter when you use several options
       of the same kind; for example, if you specify -L more than once, the
       directories are searched in the order specified.  Also, the placement of
       the -l option is significant.

       Many options have long names starting with -f or with -W---for example,
       -fmove-loop-invariants, -Wformat and so on.  Most of these have both
       positive and negative forms; the negative form of -ffoo is -fno-foo.
       This manual documents only one of these two forms, whichever one is not
       the default.

       Some options take one or more arguments typically separated either by a
       space or by the equals sign (=) from the option name.  Unless documented
       otherwise, an argument can be either numeric or a string.  Numeric
       arguments must typically be small unsigned decimal or hexadecimal
       integers.  Hexadecimal arguments must begin with the 0x prefix.
       Arguments to options that specify a size threshold of some sort may be
       arbitrarily large decimal or hexadecimal integers followed by a byte size
       suffix designating a multiple of bytes such as "kB" and "KiB" for
       kilobyte and kibibyte, respectively, "MB" and "MiB" for megabyte and
       mebibyte, "GB" and "GiB" for gigabyte and gigibyte, and so on.  Such
       arguments are designated by byte-size in the following text.  Refer to
       the NIST, IEC, and other relevant national and international standards
       for the full listing and explanation of the binary and decimal byte size
       prefixes.

OPTIONS
   Option Summary
       Here is a summary of all the options, grouped by type.  Explanations are
       in the following sections.

       Overall Options
           -c  -S  -E  -o file -dumpbase dumpbase  -dumpbase-ext auxdropsuf
           -dumpdir dumppfx  -x language -v  -###  --help[=class[,...]]
           --target-help  --version -pass-exit-codes  -pipe  -specs=file
           -wrapper @file  -ffile-prefix-map=old=new -fplugin=file
           -fplugin-arg-name=arg -fdump-ada-spec[-slim]  -fada-spec-parent=unit
           -fdump-go-spec=file

       C Language Options
           -ansi  -std=standard  -fgnu89-inline
           -fpermitted-flt-eval-methods=standard -aux-info filename
           -fallow-parameterless-variadic-functions -fno-asm  -fno-builtin
           -fno-builtin-function  -fgimple -fhosted  -ffreestanding -fopenacc
           -fopenacc-dim=geom -fopenmp  -fopenmp-simd -fms-extensions
           -fplan9-extensions  -fsso-struct=endianness -fallow-single-precision
           -fcond-mismatch  -flax-vector-conversions -fsigned-bitfields
           -fsigned-char -funsigned-bitfields  -funsigned-char

       C++ Language Options
           -fabi-version=n  -fno-access-control -faligned-new=n
           -fargs-in-order=n  -fchar8_t  -fcheck-new -fconstexpr-depth=n
           -fconstexpr-cache-depth=n -fconstexpr-loop-limit=n
           -fconstexpr-ops-limit=n -fno-elide-constructors -fno-enforce-eh-specs
           -fno-gnu-keywords -fno-implicit-templates
           -fno-implicit-inline-templates -fno-implement-inlines
           -fmodule-header[=kind] -fmodule-only -fmodules-ts
           -fmodule-implicit-inline -fno-module-lazy
           -fmodule-mapper=specification -fmodule-version-ignore -fms-extensions
           -fnew-inheriting-ctors -fnew-ttp-matching -fno-nonansi-builtins
           -fnothrow-opt  -fno-operator-names -fno-optional-diags  -fpermissive
           -fno-pretty-templates -fno-rtti  -fsized-deallocation
           -ftemplate-backtrace-limit=n -ftemplate-depth=n
           -fno-threadsafe-statics  -fuse-cxa-atexit -fno-weak  -nostdinc++
           -fvisibility-inlines-hidden -fvisibility-ms-compat
           -fext-numeric-literals -flang-info-include-translate[=header]
           -flang-info-include-translate-not -flang-info-module-cmi[=module]
           -stdlib=libstdc++,libc++ -Wabi-tag  -Wcatch-value  -Wcatch-value=n
           -Wno-class-conversion  -Wclass-memaccess -Wcomma-subscript
           -Wconditionally-supported -Wno-conversion-null
           -Wctad-maybe-unsupported -Wctor-dtor-privacy  -Wno-delete-incomplete
           -Wdelete-non-virtual-dtor  -Wdeprecated-copy -Wdeprecated-copy-dtor
           -Wno-deprecated-enum-enum-conversion
           -Wno-deprecated-enum-float-conversion -Weffc++  -Wno-exceptions
           -Wextra-semi  -Wno-inaccessible-base -Wno-inherited-variadic-ctor
           -Wno-init-list-lifetime -Winvalid-imported-macros
           -Wno-invalid-offsetof  -Wno-literal-suffix -Wno-mismatched-new-delete
           -Wmismatched-tags -Wmultiple-inheritance  -Wnamespaces  -Wnarrowing
           -Wnoexcept  -Wnoexcept-type  -Wnon-virtual-dtor -Wpessimizing-move
           -Wno-placement-new  -Wplacement-new=n -Wrange-loop-construct
           -Wredundant-move -Wredundant-tags -Wreorder  -Wregister
           -Wstrict-null-sentinel  -Wno-subobject-linkage  -Wtemplates
           -Wno-non-template-friend  -Wold-style-cast -Woverloaded-virtual
           -Wno-pmf-conversions -Wsign-promo -Wsized-deallocation
           -Wsuggest-final-methods -Wsuggest-final-types  -Wsuggest-override
           -Wno-terminate  -Wuseless-cast  -Wno-vexing-parse
           -Wvirtual-inheritance -Wno-virtual-move-assign  -Wvolatile
           -Wzero-as-null-pointer-constant

       Objective-C and Objective-C++ Language Options
           -fconstant-string-class=class-name -fgnu-runtime  -fnext-runtime
           -fno-nil-receivers -fobjc-abi-version=n -fobjc-call-cxx-cdtors
           -fobjc-direct-dispatch -fobjc-exceptions -fobjc-gc -fobjc-nilcheck
           -fobjc-std=objc1 -fno-local-ivars
           -fivar-visibility=[public|protected|private|package]
           -freplace-objc-classes -fzero-link -gen-decls -Wassign-intercept
           -Wno-property-assign-default -Wno-protocol -Wobjc-root-class
           -Wselector -Wstrict-selector-match -Wundeclared-selector

       Diagnostic Message Formatting Options
           -fmessage-length=n -fdiagnostics-plain-output
           -fdiagnostics-show-location=[once|every-line]
           -fdiagnostics-color=[auto|never|always]
           -fdiagnostics-urls=[auto|never|always]
           -fdiagnostics-format=[text|json] -fno-diagnostics-show-option
           -fno-diagnostics-show-caret -fno-diagnostics-show-labels
           -fno-diagnostics-show-line-numbers -fno-diagnostics-show-cwe
           -fdiagnostics-minimum-margin-width=width
           -fdiagnostics-parseable-fixits  -fdiagnostics-generate-patch
           -fdiagnostics-show-template-tree  -fno-elide-type
           -fdiagnostics-path-format=[none|separate-events|inline-events]
           -fdiagnostics-show-path-depths -fno-show-column
           -fdiagnostics-column-unit=[display|byte]
           -fdiagnostics-column-origin=origin

       Warning Options
           -fsyntax-only  -fmax-errors=n  -Wpedantic -pedantic-errors -w
           -Wextra  -Wall  -Wabi=n -Waddress  -Wno-address-of-packed-member
           -Waggregate-return -Walloc-size-larger-than=byte-size  -Walloc-zero
           -Walloca  -Walloca-larger-than=byte-size
           -Wno-aggressive-loop-optimizations -Warith-conversion -Warray-bounds
           -Warray-bounds=n -Wno-attributes  -Wattribute-alias=n
           -Wno-attribute-alias -Wno-attribute-warning  -Wbool-compare
           -Wbool-operation -Wno-builtin-declaration-mismatch
           -Wno-builtin-macro-redefined  -Wc90-c99-compat  -Wc99-c11-compat
           -Wc11-c2x-compat -Wc++-compat  -Wc++11-compat  -Wc++14-compat
           -Wc++17-compat -Wc++20-compat -Wcast-align  -Wcast-align=strict
           -Wcast-function-type  -Wcast-qual -Wchar-subscripts -Wclobbered
           -Wcomment -Wconversion  -Wno-coverage-mismatch  -Wno-cpp
           -Wdangling-else  -Wdate-time -Wno-deprecated
           -Wno-deprecated-declarations  -Wno-designated-init
           -Wdisabled-optimization -Wno-discarded-array-qualifiers
           -Wno-discarded-qualifiers -Wno-div-by-zero  -Wdouble-promotion
           -Wduplicated-branches  -Wduplicated-cond -Wempty-body
           -Wno-endif-labels  -Wenum-compare  -Wenum-conversion -Werror
           -Werror=*  -Wexpansion-to-defined  -Wfatal-errors -Wfloat-conversion
           -Wfloat-equal  -Wformat  -Wformat=2 -Wno-format-contains-nul
           -Wno-format-extra-args -Wformat-nonliteral  -Wformat-overflow=n
           -Wformat-security  -Wformat-signedness  -Wformat-truncation=n
           -Wformat-y2k  -Wframe-address -Wframe-larger-than=byte-size
           -Wno-free-nonheap-object -Wno-if-not-aligned  -Wno-ignored-attributes
           -Wignored-qualifiers  -Wno-incompatible-pointer-types -Wimplicit
           -Wimplicit-fallthrough  -Wimplicit-fallthrough=n
           -Wno-implicit-function-declaration  -Wno-implicit-int -Winit-self
           -Winline  -Wno-int-conversion  -Wint-in-bool-context
           -Wno-int-to-pointer-cast  -Wno-invalid-memory-model -Winvalid-pch
           -Wjump-misses-init  -Wlarger-than=byte-size -Wlogical-not-parentheses
           -Wlogical-op  -Wlong-long -Wno-lto-type-mismatch -Wmain
           -Wmaybe-uninitialized -Wmemset-elt-size  -Wmemset-transposed-args
           -Wmisleading-indentation  -Wmissing-attributes  -Wmissing-braces
           -Wmissing-field-initializers  -Wmissing-format-attribute
           -Wmissing-include-dirs  -Wmissing-noreturn  -Wno-missing-profile
           -Wno-multichar  -Wmultistatement-macros  -Wnonnull  -Wnonnull-compare
           -Wnormalized=[none|id|nfc|nfkc] -Wnull-dereference  -Wno-odr
           -Wopenmp-simd -Wno-overflow  -Woverlength-strings
           -Wno-override-init-side-effects -Wpacked  -Wno-packed-bitfield-compat
           -Wpacked-not-aligned  -Wpadded -Wparentheses  -Wno-pedantic-ms-format
           -Wpointer-arith  -Wno-pointer-compare  -Wno-pointer-to-int-cast
           -Wno-pragmas  -Wno-prio-ctor-dtor  -Wredundant-decls -Wrestrict
           -Wno-return-local-addr  -Wreturn-type -Wno-scalar-storage-order
           -Wsequence-point -Wshadow  -Wshadow=global  -Wshadow=local
           -Wshadow=compatible-local -Wno-shadow-ivar -Wno-shift-count-negative
           -Wno-shift-count-overflow  -Wshift-negative-value -Wno-shift-overflow
           -Wshift-overflow=n -Wsign-compare  -Wsign-conversion
           -Wno-sizeof-array-argument -Wsizeof-array-div -Wsizeof-pointer-div
           -Wsizeof-pointer-memaccess -Wstack-protector  -Wstack-usage=byte-size
           -Wstrict-aliasing -Wstrict-aliasing=n  -Wstrict-overflow
           -Wstrict-overflow=n -Wstring-compare -Wno-stringop-overflow
           -Wno-stringop-overread -Wno-stringop-truncation
           -Wsuggest-attribute=[pure|const|noreturn|format|malloc] -Wswitch
           -Wno-switch-bool  -Wswitch-default  -Wswitch-enum
           -Wno-switch-outside-range  -Wno-switch-unreachable  -Wsync-nand
           -Wsystem-headers  -Wtautological-compare  -Wtrampolines  -Wtrigraphs
           -Wtsan -Wtype-limits  -Wundef -Wuninitialized  -Wunknown-pragmas
           -Wunsuffixed-float-constants  -Wunused -Wunused-but-set-parameter
           -Wunused-but-set-variable -Wunused-const-variable
           -Wunused-const-variable=n -Wunused-function  -Wunused-label
           -Wunused-local-typedefs -Wunused-macros -Wunused-parameter
           -Wno-unused-result -Wunused-value  -Wunused-variable -Wno-varargs
           -Wvariadic-macros -Wvector-operation-performance -Wvla
           -Wvla-larger-than=byte-size  -Wno-vla-larger-than
           -Wvolatile-register-var  -Wwrite-strings -Wzero-length-bounds

       Static Analyzer Options
           -fanalyzer -fanalyzer-call-summaries -fanalyzer-checker=name
           -fno-analyzer-feasibility -fanalyzer-fine-grained
           -fanalyzer-state-merge -fanalyzer-state-purge -fanalyzer-transitivity
           -fanalyzer-verbose-edges -fanalyzer-verbose-state-changes
           -fanalyzer-verbosity=level -fdump-analyzer -fdump-analyzer-stderr
           -fdump-analyzer-callgraph -fdump-analyzer-exploded-graph
           -fdump-analyzer-exploded-nodes -fdump-analyzer-exploded-nodes-2
           -fdump-analyzer-exploded-nodes-3 -fdump-analyzer-feasibility
           -fdump-analyzer-json -fdump-analyzer-state-purge
           -fdump-analyzer-supergraph -Wno-analyzer-double-fclose
           -Wno-analyzer-double-free -Wno-analyzer-exposure-through-output-file
           -Wno-analyzer-file-leak -Wno-analyzer-free-of-non-heap
           -Wno-analyzer-malloc-leak -Wno-analyzer-mismatching-deallocation
           -Wno-analyzer-null-argument -Wno-analyzer-null-dereference
           -Wno-analyzer-possible-null-argument
           -Wno-analyzer-possible-null-dereference
           -Wno-analyzer-shift-count-negative -Wno-analyzer-shift-count-overflow
           -Wno-analyzer-stale-setjmp-buffer -Wno-analyzer-tainted-array-index
           -Wanalyzer-too-complex
           -Wno-analyzer-unsafe-call-within-signal-handler
           -Wno-analyzer-use-after-free
           -Wno-analyzer-use-of-pointer-in-stale-stack-frame
           -Wno-analyzer-use-of-uninitialized-value -Wno-analyzer-write-to-const
           -Wno-analyzer-write-to-string-literal

       C and Objective-C-only Warning Options
           -Wbad-function-cast  -Wmissing-declarations -Wmissing-parameter-type
           -Wmissing-prototypes  -Wnested-externs -Wold-style-declaration
           -Wold-style-definition -Wstrict-prototypes  -Wtraditional
           -Wtraditional-conversion -Wdeclaration-after-statement
           -Wpointer-sign

       Debugging Options
           -g  -glevel  -gdwarf  -gdwarf-version -ggdb  -grecord-gcc-switches
           -gno-record-gcc-switches -gstabs  -gstabs+  -gstrict-dwarf
           -gno-strict-dwarf -gas-loc-support  -gno-as-loc-support
           -gas-locview-support  -gno-as-locview-support -gcolumn-info
           -gno-column-info  -gdwarf32  -gdwarf64 -gstatement-frontiers
           -gno-statement-frontiers -gvariable-location-views
           -gno-variable-location-views -ginternal-reset-location-views
           -gno-internal-reset-location-views -ginline-points
           -gno-inline-points -gvms  -gxcoff  -gxcoff+  -gz[=type] -gsplit-dwarf
           -gdescribe-dies  -gno-describe-dies -fdebug-prefix-map=old=new
           -fdebug-types-section -fno-eliminate-unused-debug-types
           -femit-struct-debug-baseonly  -femit-struct-debug-reduced
           -femit-struct-debug-detailed[=spec-list]
           -fno-eliminate-unused-debug-symbols  -femit-class-debug-always
           -fno-merge-debug-strings  -fno-dwarf2-cfi-asm -fvar-tracking
           -fvar-tracking-assignments

       Optimization Options
           -faggressive-loop-optimizations -falign-functions[=n[:m:[n2[:m2]]]]
           -falign-jumps[=n[:m:[n2[:m2]]]] -falign-labels[=n[:m:[n2[:m2]]]]
           -falign-loops[=n[:m:[n2[:m2]]]] -fno-allocation-dce
           -fallow-store-data-races -fassociative-math  -fauto-profile
           -fauto-profile[=path] -fauto-inc-dec  -fbranch-probabilities
           -fcaller-saves -fcombine-stack-adjustments  -fconserve-stack
           -fcompare-elim  -fcprop-registers  -fcrossjumping -fcse-follow-jumps
           -fcse-skip-blocks  -fcx-fortran-rules -fcx-limited-range
           -fdata-sections  -fdce  -fdelayed-branch -fdelete-null-pointer-checks
           -fdevirtualize  -fdevirtualize-speculatively -fdevirtualize-at-ltrans
           -fdse -fearly-inlining  -fipa-sra  -fexpensive-optimizations
           -ffat-lto-objects -ffast-math  -ffinite-math-only  -ffloat-store
           -fexcess-precision=style -ffinite-loops -fforward-propagate
           -ffp-contract=style  -ffunction-sections -fgcse  -fgcse-after-reload
           -fgcse-las  -fgcse-lm  -fgraphite-identity -fgcse-sm
           -fhoist-adjacent-loads  -fif-conversion -fif-conversion2
           -findirect-inlining -finline-functions
           -finline-functions-called-once  -finline-limit=n
           -finline-small-functions -fipa-modref -fipa-cp  -fipa-cp-clone
           -fipa-bit-cp  -fipa-vrp  -fipa-pta  -fipa-profile  -fipa-pure-const
           -fipa-reference  -fipa-reference-addressable -fipa-stack-alignment
           -fipa-icf  -fira-algorithm=algorithm -flive-patching=level
           -fira-region=region  -fira-hoist-pressure -fira-loop-pressure
           -fno-ira-share-save-slots -fno-ira-share-spill-slots
           -fisolate-erroneous-paths-dereference
           -fisolate-erroneous-paths-attribute -fivopts  -fkeep-inline-functions
           -fkeep-static-functions -fkeep-static-consts
           -flimit-function-alignment  -flive-range-shrinkage -floop-block
           -floop-interchange  -floop-strip-mine -floop-unroll-and-jam
           -floop-nest-optimize -floop-parallelize-all  -flra-remat  -flto
           -flto-compression-level -flto-partition=alg  -fmerge-all-constants
           -fmerge-constants  -fmodulo-sched  -fmodulo-sched-allow-regmoves
           -fmove-loop-invariants  -fno-branch-count-reg -fno-defer-pop
           -fno-fp-int-builtin-inexact  -fno-function-cse
           -fno-guess-branch-probability  -fno-inline  -fno-math-errno
           -fno-peephole -fno-peephole2  -fno-printf-return-value
           -fno-sched-interblock -fno-sched-spec  -fno-signed-zeros
           -fno-toplevel-reorder  -fno-trapping-math
           -fno-zero-initialized-in-bss -fomit-frame-pointer
           -foptimize-sibling-calls -fpartial-inlining  -fpeel-loops
           -fpredictive-commoning -fprefetch-loop-arrays -fprofile-correction
           -fprofile-use  -fprofile-use=path -fprofile-partial-training
           -fprofile-values -fprofile-reorder-functions -freciprocal-math  -free
           -frename-registers  -freorder-blocks
           -freorder-blocks-algorithm=algorithm -freorder-blocks-and-partition
           -freorder-functions -frerun-cse-after-loop
           -freschedule-modulo-scheduled-loops -frounding-math
           -fsave-optimization-record -fsched2-use-superblocks  -fsched-pressure
           -fsched-spec-load  -fsched-spec-load-dangerous
           -fsched-stalled-insns-dep[=n]  -fsched-stalled-insns[=n]
           -fsched-group-heuristic  -fsched-critical-path-heuristic
           -fsched-spec-insn-heuristic  -fsched-rank-heuristic
           -fsched-last-insn-heuristic  -fsched-dep-count-heuristic
           -fschedule-fusion -fschedule-insns  -fschedule-insns2
           -fsection-anchors -fselective-scheduling  -fselective-scheduling2
           -fsel-sched-pipelining  -fsel-sched-pipelining-outer-loops
           -fsemantic-interposition  -fshrink-wrap  -fshrink-wrap-separate
           -fsignaling-nans -fsingle-precision-constant  -fsplit-ivs-in-unroller
           -fsplit-loops -fsplit-paths -fsplit-wide-types
           -fsplit-wide-types-early  -fssa-backprop  -fssa-phiopt -fstdarg-opt
           -fstore-merging  -fstrict-aliasing -fthread-jumps  -ftracer
           -ftree-bit-ccp -ftree-builtin-call-dce  -ftree-ccp  -ftree-ch
           -ftree-coalesce-vars  -ftree-copy-prop  -ftree-dce
           -ftree-dominator-opts -ftree-dse  -ftree-forwprop  -ftree-fre
           -fcode-hoisting -ftree-loop-if-convert  -ftree-loop-im -ftree-phiprop
           -ftree-loop-distribution  -ftree-loop-distribute-patterns
           -ftree-loop-ivcanon  -ftree-loop-linear  -ftree-loop-optimize
           -ftree-loop-vectorize -ftree-parallelize-loops=n  -ftree-pre
           -ftree-partial-pre  -ftree-pta -ftree-reassoc  -ftree-scev-cprop
           -ftree-sink  -ftree-slsr  -ftree-sra -ftree-switch-conversion
           -ftree-tail-merge -ftree-ter  -ftree-vectorize  -ftree-vrp
           -funconstrained-commons -funit-at-a-time  -funroll-all-loops
           -funroll-loops -funsafe-math-optimizations  -funswitch-loops -fipa-ra
           -fvariable-expansion-in-unroller  -fvect-cost-model  -fvpt -fweb
           -fwhole-program  -fwpa  -fuse-linker-plugin -fzero-call-used-regs
           --param name=value -O  -O0  -O1  -O2  -O3  -Os  -Ofast  -Og

       Program Instrumentation Options
           -p  -pg  -fprofile-arcs  --coverage  -ftest-coverage
           -fprofile-abs-path -fprofile-dir=path  -fprofile-generate
           -fprofile-generate=path -fprofile-info-section
           -fprofile-info-section=name -fprofile-note=path
           -fprofile-prefix-path=path -fprofile-update=method
           -fprofile-filter-files=regex -fprofile-exclude-files=regex
           -fprofile-reproducible=[multithreaded|parallel-runs|serial]
           -fsanitize=style  -fsanitize-recover  -fsanitize-recover=style
           -fasan-shadow-offset=number  -fsanitize-sections=s1,s2,...
           -fsanitize-undefined-trap-on-error  -fbounds-check
           -fcf-protection=[full|branch|return|none|check] -fstack-protector
           -fstack-protector-all  -fstack-protector-strong
           -fstack-protector-explicit  -fstack-check -fstack-limit-register=reg
           -fstack-limit-symbol=sym -fno-stack-limit  -fsplit-stack
           -fvtable-verify=[std|preinit|none] -fvtv-counts  -fvtv-debug
           -finstrument-functions
           -finstrument-functions-exclude-function-list=sym,sym,...
           -finstrument-functions-exclude-file-list=file,file,...

       Preprocessor Options
           -Aquestion=answer -A-question[=answer] -C  -CC  -Dmacro[=defn] -dD
           -dI  -dM  -dN  -dU -fdebug-cpp  -fdirectives-only
           -fdollars-in-identifiers -fexec-charset=charset
           -fextended-identifiers -finput-charset=charset  -flarge-source-files
           -fmacro-prefix-map=old=new -fmax-include-depth=depth
           -fno-canonical-system-headers  -fpch-deps  -fpch-preprocess
           -fpreprocessed  -ftabstop=width  -ftrack-macro-expansion
           -fwide-exec-charset=charset  -fworking-directory -H  -imacros file
           -include file -M  -MD  -MF  -MG  -MM  -MMD  -MP  -MQ  -MT
           -Mno-modules -no-integrated-cpp  -P  -pthread  -remap -traditional
           -traditional-cpp  -trigraphs -Umacro  -undef -Wp,option
           -Xpreprocessor option

       Assembler Options
           -Wa,option  -Xassembler option

       Linker Options
           object-file-name  -fuse-ld=linker  -llibrary -nostartfiles
           -nodefaultlibs  -nolibc  -nostdlib -e entry  --entry=entry -pie
           -pthread  -r  -rdynamic -s  -static  -static-pie  -static-libgcc
           -static-libstdc++ -static-libasan  -static-libtsan  -static-liblsan
           -static-libubsan -shared  -shared-libgcc  -symbolic -T script
           -Wl,option  -Xlinker option -u symbol  -z keyword

       Directory Options
           -Bprefix  -Idir  -I- -idirafter dir -imacros file  -imultilib dir
           -iplugindir=dir  -iprefix file -iquote dir  -isysroot dir  -isystem
           dir -iwithprefix dir  -iwithprefixbefore dir -Ldir
           -no-canonical-prefixes  --no-sysroot-suffix -nostdinc  -nostdinc++
           --sysroot=dir

       Code Generation Options
           -fcall-saved-reg  -fcall-used-reg -ffixed-reg  -fexceptions
           -fnon-call-exceptions  -fdelete-dead-exceptions  -funwind-tables
           -fasynchronous-unwind-tables -fno-gnu-unique -finhibit-size-directive
           -fcommon  -fno-ident -fpcc-struct-return  -fpic  -fPIC  -fpie  -fPIE
           -fno-plt -fno-jump-tables -fno-bit-tests -frecord-gcc-switches
           -freg-struct-return  -fshort-enums  -fshort-wchar -fverbose-asm
           -fpack-struct[=n] -fleading-underscore  -ftls-model=model
           -fstack-reuse=reuse_level -ftrampolines  -ftrapv  -fwrapv
           -fvisibility=[default|internal|hidden|protected]
           -fstrict-volatile-bitfields  -fsync-libcalls

       Developer Options
           -dletters  -dumpspecs  -dumpmachine  -dumpversion -dumpfullversion
           -fcallgraph-info[=su,da] -fchecking  -fchecking=n -fdbg-cnt-list
           -fdbg-cnt=counter-value-list -fdisable-ipa-pass_name
           -fdisable-rtl-pass_name -fdisable-rtl-pass-name=range-list
           -fdisable-tree-pass_name -fdisable-tree-pass-name=range-list
           -fdump-debug  -fdump-earlydebug -fdump-noaddr  -fdump-unnumbered
           -fdump-unnumbered-links -fdump-final-insns[=file] -fdump-ipa-all
           -fdump-ipa-cgraph  -fdump-ipa-inline -fdump-lang-all
           -fdump-lang-switch -fdump-lang-switch-options
           -fdump-lang-switch-options=filename -fdump-passes -fdump-rtl-pass
           -fdump-rtl-pass=filename -fdump-statistics -fdump-tree-all
           -fdump-tree-switch -fdump-tree-switch-options
           -fdump-tree-switch-options=filename -fcompare-debug[=opts]
           -fcompare-debug-second -fenable-kind-pass -fenable-kind-pass=range-
           list -fira-verbose=n -flto-report  -flto-report-wpa  -fmem-report-wpa
           -fmem-report  -fpre-ipa-mem-report  -fpost-ipa-mem-report -fopt-info
           -fopt-info-options[=file] -fprofile-report -frandom-seed=string
           -fsched-verbose=n -fsel-sched-verbose  -fsel-sched-dump-cfg
           -fsel-sched-pipelining-verbose -fstats  -fstack-usage  -ftime-report
           -ftime-report-details -fvar-tracking-assignments-toggle  -gtoggle
           -print-file-name=library  -print-libgcc-file-name
           -print-multi-directory  -print-multi-lib  -print-multi-os-directory
           -print-prog-name=program  -print-search-dirs  -Q -print-sysroot
           -print-sysroot-headers-suffix -save-temps  -save-temps=cwd
           -save-temps=obj  -time[=file]

       Machine-Dependent Options
           AArch64 Options -mabi=name  -mbig-endian  -mlittle-endian
           -mgeneral-regs-only -mcmodel=tiny  -mcmodel=small  -mcmodel=large
           -mstrict-align  -mno-strict-align -momit-leaf-frame-pointer
           -mtls-dialect=desc  -mtls-dialect=traditional -mtls-size=size
           -mfix-cortex-a53-835769  -mfix-cortex-a53-843419
           -mlow-precision-recip-sqrt  -mlow-precision-sqrt  -mlow-precision-div
           -mpc-relative-literal-loads -msign-return-address=scope
           -mbranch-protection=none|standard|pac-ret[+leaf +b-key]|bti
           -mharden-sls=opts -march=name  -mcpu=name  -mtune=name
           -moverride=string  -mverbose-cost-dump -mstack-protector-guard=guard
           -mstack-protector-guard-reg=sysreg
           -mstack-protector-guard-offset=offset -mtrack-speculation
           -moutline-atomics

           Adapteva Epiphany Options -mhalf-reg-file  -mprefer-short-insn-regs
           -mbranch-cost=num  -mcmove  -mnops=num  -msoft-cmpsf -msplit-lohi
           -mpost-inc  -mpost-modify  -mstack-offset=num -mround-nearest
           -mlong-calls  -mshort-calls  -msmall16 -mfp-mode=mode  -mvect-double
           -max-vect-align=num -msplit-vecmove-early  -m1reg-reg

           AMD GCN Options -march=gpu -mtune=gpu -mstack-size=bytes

           ARC Options -mbarrel-shifter  -mjli-always -mcpu=cpu  -mA6  -mARC600
           -mA7  -mARC700 -mdpfp  -mdpfp-compact  -mdpfp-fast  -mno-dpfp-lrsr
           -mea  -mno-mpy  -mmul32x16  -mmul64  -matomic -mnorm  -mspfp
           -mspfp-compact  -mspfp-fast  -msimd  -msoft-float  -mswap -mcrc
           -mdsp-packa  -mdvbf  -mlock  -mmac-d16  -mmac-24  -mrtsc  -mswape
           -mtelephony  -mxy  -misize  -mannotate-align  -marclinux
           -marclinux_prof -mlong-calls  -mmedium-calls  -msdata
           -mirq-ctrl-saved -mrgf-banked-regs  -mlpc-width=width  -G num
           -mvolatile-cache  -mtp-regno=regno -malign-call  -mauto-modify-reg
           -mbbit-peephole  -mno-brcc -mcase-vector-pcrel  -mcompact-casesi
           -mno-cond-exec  -mearly-cbranchsi -mexpand-adddi  -mindexed-loads
           -mlra  -mlra-priority-none -mlra-priority-compact mlra-priority-
           noncompact  -mmillicode -mmixed-code  -mq-class  -mRcq  -mRcw
           -msize-level=level -mtune=cpu  -mmultcost=num  -mcode-density-frame
           -munalign-prob-threshold=probability  -mmpy-option=multo -mdiv-rem
           -mcode-density  -mll64  -mfpu=fpu  -mrf16  -mbranch-index

           ARM Options -mapcs-frame  -mno-apcs-frame -mabi=name
           -mapcs-stack-check  -mno-apcs-stack-check -mapcs-reentrant
           -mno-apcs-reentrant -mgeneral-regs-only -msched-prolog
           -mno-sched-prolog -mlittle-endian  -mbig-endian -mbe8  -mbe32
           -mfloat-abi=name -mfp16-format=name -mthumb-interwork
           -mno-thumb-interwork -mcpu=name  -march=name  -mfpu=name -mtune=name
           -mprint-tune-info -mstructure-size-boundary=n -mabort-on-noreturn
           -mlong-calls  -mno-long-calls -msingle-pic-base  -mno-single-pic-base
           -mpic-register=reg -mnop-fun-dllimport -mpoke-function-name -mthumb
           -marm  -mflip-thumb -mtpcs-frame  -mtpcs-leaf-frame
           -mcaller-super-interworking  -mcallee-super-interworking -mtp=name
           -mtls-dialect=dialect -mword-relocations -mfix-cortex-m3-ldrd
           -munaligned-access -mneon-for-64bits -mslow-flash-data
           -masm-syntax-unified -mrestrict-it -mverbose-cost-dump -mpure-code
           -mcmse -mfdpic

           AVR Options -mmcu=mcu  -mabsdata  -maccumulate-args
           -mbranch-cost=cost -mcall-prologues  -mgas-isr-prologues  -mint8
           -mdouble=bits -mlong-double=bits -mn_flash=size  -mno-interrupts
           -mmain-is-OS_task  -mrelax  -mrmw  -mstrict-X  -mtiny-stack
           -mfract-convert-truncate -mshort-calls  -nodevicelib  -nodevicespecs
           -Waddr-space-convert  -Wmisspelled-isr

           Blackfin Options -mcpu=cpu[-sirevision] -msim
           -momit-leaf-frame-pointer  -mno-omit-leaf-frame-pointer
           -mspecld-anomaly  -mno-specld-anomaly  -mcsync-anomaly
           -mno-csync-anomaly -mlow-64k  -mno-low64k  -mstack-check-l1
           -mid-shared-library -mno-id-shared-library  -mshared-library-id=n
           -mleaf-id-shared-library  -mno-leaf-id-shared-library -msep-data
           -mno-sep-data  -mlong-calls  -mno-long-calls -mfast-fp  -minline-plt
           -mmulticore  -mcorea  -mcoreb  -msdram -micplb

           C6X Options -mbig-endian  -mlittle-endian  -march=cpu -msim
           -msdata=sdata-type

           CRIS Options -mcpu=cpu  -march=cpu  -mtune=cpu -mmax-stack-frame=n
           -melinux-stacksize=n -metrax4  -metrax100  -mpdebug  -mcc-init
           -mno-side-effects -mstack-align  -mdata-align  -mconst-align -m32-bit
           -m16-bit  -m8-bit  -mno-prologue-epilogue  -mno-gotplt -melf  -maout
           -melinux  -mlinux  -sim  -sim2 -mmul-bug-workaround
           -mno-mul-bug-workaround

           CR16 Options -mmac -mcr16cplus  -mcr16c -msim  -mint32  -mbit-ops
           -mdata-model=model

           C-SKY Options -march=arch  -mcpu=cpu -mbig-endian  -EB
           -mlittle-endian  -EL -mhard-float  -msoft-float  -mfpu=fpu
           -mdouble-float  -mfdivdu -mfloat-abi=name -melrw  -mistack  -mmp
           -mcp  -mcache  -msecurity  -mtrust -mdsp  -medsp  -mvdsp -mdiv
           -msmart  -mhigh-registers  -manchor -mpushpop  -mmultiple-stld
           -mconstpool  -mstack-size  -mccrt -mbranch-cost=n  -mcse-cc
           -msched-prolog -msim

           Darwin Options -all_load  -allowable_client  -arch
           -arch_errors_fatal -arch_only  -bind_at_load  -bundle  -bundle_loader
           -client_name  -compatibility_version  -current_version -dead_strip
           -dependency-file  -dylib_file  -dylinker_install_name -dynamic
           -dynamiclib  -exported_symbols_list -filelist  -flat_namespace
           -force_cpusubtype_ALL -force_flat_namespace
           -headerpad_max_install_names -iframework -image_base  -init
           -install_name  -keep_private_externs -multi_module  -multiply_defined
           -multiply_defined_unused -noall_load   -no_dead_strip_inits_and_terms
           -nofixprebinding  -nomultidefs  -noprebind  -noseglinkedit
           -pagezero_size  -prebind  -prebind_all_twolevel_modules
           -private_bundle  -read_only_relocs  -sectalign -sectobjectsymbols
           -whyload  -seg1addr -sectcreate  -sectobjectsymbols  -sectorder
           -segaddr  -segs_read_only_addr  -segs_read_write_addr -seg_addr_table
           -seg_addr_table_filename  -seglinkedit -segprot  -segs_read_only_addr
           -segs_read_write_addr -single_module  -static  -sub_library
           -sub_umbrella -twolevel_namespace  -umbrella  -undefined
           -unexported_symbols_list  -weak_reference_mismatches -whatsloaded  -F
           -gused  -gfull  -mmacosx-version-min=version -mkernel
           -mone-byte-bool

           DEC Alpha Options -mno-fp-regs  -msoft-float -mieee
           -mieee-with-inexact  -mieee-conformant -mfp-trap-mode=mode
           -mfp-rounding-mode=mode -mtrap-precision=mode  -mbuild-constants
           -mcpu=cpu-type  -mtune=cpu-type -mbwx  -mmax  -mfix  -mcix
           -mfloat-vax  -mfloat-ieee -mexplicit-relocs  -msmall-data
           -mlarge-data -msmall-text  -mlarge-text -mmemory-latency=time

           eBPF Options -mbig-endian -mlittle-endian -mkernel=version
           -mframe-limit=bytes -mxbpf

           FR30 Options -msmall-model  -mno-lsim

           FT32 Options -msim  -mlra  -mnodiv  -mft32b  -mcompress  -mnopm

           FRV Options -mgpr-32  -mgpr-64  -mfpr-32  -mfpr-64 -mhard-float
           -msoft-float -malloc-cc  -mfixed-cc  -mdword  -mno-dword -mdouble
           -mno-double -mmedia  -mno-media  -mmuladd  -mno-muladd -mfdpic
           -minline-plt  -mgprel-ro  -multilib-library-pic -mlinked-fp
           -mlong-calls  -malign-labels -mlibrary-pic  -macc-4  -macc-8 -mpack
           -mno-pack  -mno-eflags  -mcond-move  -mno-cond-move -moptimize-membar
           -mno-optimize-membar -mscc  -mno-scc  -mcond-exec  -mno-cond-exec
           -mvliw-branch  -mno-vliw-branch -mmulti-cond-exec
           -mno-multi-cond-exec  -mnested-cond-exec -mno-nested-cond-exec
           -mtomcat-stats -mTLS  -mtls -mcpu=cpu

           GNU/Linux Options -mglibc  -muclibc  -mmusl  -mbionic  -mandroid
           -tno-android-cc  -tno-android-ld

           H8/300 Options -mrelax  -mh  -ms  -mn  -mexr  -mno-exr  -mint32
           -malign-300

           HPPA Options -march=architecture-type -mcaller-copies
           -mdisable-fpregs  -mdisable-indexing -mfast-indirect-calls  -mgas
           -mgnu-ld   -mhp-ld -mfixed-range=register-range -mjump-in-delay
           -mlinker-opt  -mlong-calls -mlong-load-store  -mno-disable-fpregs
           -mno-disable-indexing  -mno-fast-indirect-calls  -mno-gas
           -mno-jump-in-delay  -mno-long-load-store -mno-portable-runtime
           -mno-soft-float -mno-space-regs  -msoft-float  -mpa-risc-1-0
           -mpa-risc-1-1  -mpa-risc-2-0  -mportable-runtime -mschedule=cpu-type
           -mspace-regs  -msio  -mwsio -munix=unix-std  -nolibdld  -static
           -threads

           IA-64 Options -mbig-endian  -mlittle-endian  -mgnu-as  -mgnu-ld
           -mno-pic -mvolatile-asm-stop  -mregister-names  -msdata  -mno-sdata
           -mconstant-gp  -mauto-pic  -mfused-madd
           -minline-float-divide-min-latency
           -minline-float-divide-max-throughput -mno-inline-float-divide
           -minline-int-divide-min-latency -minline-int-divide-max-throughput
           -mno-inline-int-divide -minline-sqrt-min-latency
           -minline-sqrt-max-throughput -mno-inline-sqrt -mdwarf2-asm
           -mearly-stop-bits -mfixed-range=register-range  -mtls-size=tls-size
           -mtune=cpu-type  -milp32  -mlp64 -msched-br-data-spec
           -msched-ar-data-spec  -msched-control-spec -msched-br-in-data-spec
           -msched-ar-in-data-spec  -msched-in-control-spec -msched-spec-ldc
           -msched-spec-control-ldc -msched-prefer-non-data-spec-insns
           -msched-prefer-non-control-spec-insns
           -msched-stop-bits-after-every-cycle
           -msched-count-spec-in-critical-path
           -msel-sched-dont-check-control-spec  -msched-fp-mem-deps-zero-cost
           -msched-max-memory-insns-hard-limit  -msched-max-memory-insns=max-
           insns

           LM32 Options -mbarrel-shift-enabled  -mdivide-enabled
           -mmultiply-enabled -msign-extend-enabled  -muser-enabled

           M32R/D Options -m32r2  -m32rx  -m32r -mdebug -malign-loops
           -mno-align-loops -missue-rate=number -mbranch-cost=number
           -mmodel=code-size-model-type -msdata=sdata-type -mno-flush-func
           -mflush-func=name -mno-flush-trap  -mflush-trap=number -G num

           M32C Options -mcpu=cpu  -msim  -memregs=number

           M680x0 Options -march=arch  -mcpu=cpu  -mtune=tune -m68000  -m68020
           -m68020-40  -m68020-60  -m68030  -m68040 -m68060  -mcpu32  -m5200
           -m5206e  -m528x  -m5307  -m5407 -mcfv4e  -mbitfield  -mno-bitfield
           -mc68000  -mc68020 -mnobitfield  -mrtd  -mno-rtd  -mdiv  -mno-div
           -mshort -mno-short  -mhard-float  -m68881  -msoft-float  -mpcrel
           -malign-int  -mstrict-align  -msep-data  -mno-sep-data
           -mshared-library-id=n  -mid-shared-library  -mno-id-shared-library
           -mxgot  -mno-xgot  -mlong-jump-table-offsets

           MCore Options -mhardlit  -mno-hardlit  -mdiv  -mno-div
           -mrelax-immediates -mno-relax-immediates  -mwide-bitfields
           -mno-wide-bitfields -m4byte-functions  -mno-4byte-functions
           -mcallgraph-data -mno-callgraph-data  -mslow-bytes  -mno-slow-bytes
           -mno-lsim -mlittle-endian  -mbig-endian  -m210  -m340
           -mstack-increment

           MeP Options -mabsdiff  -mall-opts  -maverage  -mbased=n  -mbitops
           -mc=n  -mclip  -mconfig=name  -mcop  -mcop32  -mcop64  -mivc2 -mdc
           -mdiv  -meb  -mel  -mio-volatile  -ml  -mleadz  -mm  -mminmax -mmult
           -mno-opts  -mrepeat  -ms  -msatur  -msdram  -msim  -msimnovec  -mtf
           -mtiny=n

           MicroBlaze Options -msoft-float  -mhard-float  -msmall-divides
           -mcpu=cpu -mmemcpy  -mxl-soft-mul  -mxl-soft-div  -mxl-barrel-shift
           -mxl-pattern-compare  -mxl-stack-check  -mxl-gp-opt  -mno-clearbss
           -mxl-multiply-high  -mxl-float-convert  -mxl-float-sqrt -mbig-endian
           -mlittle-endian  -mxl-reorder  -mxl-mode-app-model
           -mpic-data-is-text-relative

           MIPS Options -EL  -EB  -march=arch  -mtune=arch -mips1  -mips2
           -mips3  -mips4  -mips32  -mips32r2  -mips32r3  -mips32r5 -mips32r6
           -mips64  -mips64r2  -mips64r3  -mips64r5  -mips64r6 -mips16
           -mno-mips16  -mflip-mips16 -minterlink-compressed
           -mno-interlink-compressed -minterlink-mips16  -mno-interlink-mips16
           -mabi=abi  -mabicalls  -mno-abicalls -mshared  -mno-shared  -mplt
           -mno-plt  -mxgot  -mno-xgot -mgp32  -mgp64  -mfp32  -mfpxx  -mfp64
           -mhard-float  -msoft-float -mno-float  -msingle-float  -mdouble-float
           -modd-spreg  -mno-odd-spreg -mabs=mode  -mnan=encoding -mdsp
           -mno-dsp  -mdspr2  -mno-dspr2 -mmcu  -mmno-mcu -meva  -mno-eva -mvirt
           -mno-virt -mxpa  -mno-xpa -mcrc  -mno-crc -mginv  -mno-ginv
           -mmicromips  -mno-micromips -mmsa  -mno-msa -mloongson-mmi
           -mno-loongson-mmi -mloongson-ext  -mno-loongson-ext -mloongson-ext2
           -mno-loongson-ext2 -mfpu=fpu-type -msmartmips  -mno-smartmips
           -mpaired-single  -mno-paired-single  -mdmx  -mno-mdmx -mips3d
           -mno-mips3d  -mmt  -mno-mt  -mllsc  -mno-llsc -mlong64  -mlong32
           -msym32  -mno-sym32 -Gnum  -mlocal-sdata  -mno-local-sdata
           -mextern-sdata  -mno-extern-sdata  -mgpopt  -mno-gopt -membedded-data
           -mno-embedded-data -muninit-const-in-rodata
           -mno-uninit-const-in-rodata -mcode-readable=setting -msplit-addresses
           -mno-split-addresses -mexplicit-relocs  -mno-explicit-relocs
           -mcheck-zero-division  -mno-check-zero-division -mdivide-traps
           -mdivide-breaks -mload-store-pairs  -mno-load-store-pairs -mmemcpy
           -mno-memcpy  -mlong-calls  -mno-long-calls -mmad  -mno-mad  -mimadd
           -mno-imadd  -mfused-madd  -mno-fused-madd  -nocpp -mfix-24k
           -mno-fix-24k -mfix-r4000  -mno-fix-r4000  -mfix-r4400  -mno-fix-r4400
           -mfix-r5900  -mno-fix-r5900 -mfix-r10000  -mno-fix-r10000
           -mfix-rm7000  -mno-fix-rm7000 -mfix-vr4120  -mno-fix-vr4120
           -mfix-vr4130  -mno-fix-vr4130  -mfix-sb1  -mno-fix-sb1
           -mflush-func=func  -mno-flush-func -mbranch-cost=num  -mbranch-likely
           -mno-branch-likely -mcompact-branches=policy -mfp-exceptions
           -mno-fp-exceptions -mvr4130-align  -mno-vr4130-align  -msynci
           -mno-synci -mlxc1-sxc1  -mno-lxc1-sxc1  -mmadd4  -mno-madd4
           -mrelax-pic-calls  -mno-relax-pic-calls  -mmcount-ra-address
           -mframe-header-opt  -mno-frame-header-opt

           MMIX Options -mlibfuncs  -mno-libfuncs  -mepsilon  -mno-epsilon
           -mabi=gnu -mabi=mmixware  -mzero-extend  -mknuthdiv
           -mtoplevel-symbols -melf  -mbranch-predict  -mno-branch-predict
           -mbase-addresses -mno-base-addresses  -msingle-exit  -mno-single-exit

           MN10300 Options -mmult-bug  -mno-mult-bug -mno-am33  -mam33  -mam33-2
           -mam34 -mtune=cpu-type -mreturn-pointer-on-d0 -mno-crt0  -mrelax
           -mliw  -msetlb

           Moxie Options -meb  -mel  -mmul.x  -mno-crt0

           MSP430 Options -msim  -masm-hex  -mmcu=  -mcpu=  -mlarge  -msmall
           -mrelax -mwarn-mcu -mcode-region=  -mdata-region= -msilicon-errata=
           -msilicon-errata-warn= -mhwmult=  -minrt  -mtiny-printf
           -mmax-inline-shift=

           NDS32 Options -mbig-endian  -mlittle-endian -mreduced-regs
           -mfull-regs -mcmov  -mno-cmov -mext-perf  -mno-ext-perf -mext-perf2
           -mno-ext-perf2 -mext-string  -mno-ext-string -mv3push  -mno-v3push
           -m16bit  -mno-16bit -misr-vector-size=num -mcache-block-size=num
           -march=arch -mcmodel=code-model -mctor-dtor  -mrelax

           Nios II Options -G num  -mgpopt=option  -mgpopt  -mno-gpopt
           -mgprel-sec=regexp  -mr0rel-sec=regexp -mel  -meb -mno-bypass-cache
           -mbypass-cache -mno-cache-volatile  -mcache-volatile -mno-fast-sw-div
           -mfast-sw-div -mhw-mul  -mno-hw-mul  -mhw-mulx  -mno-hw-mulx
           -mno-hw-div  -mhw-div -mcustom-insn=N  -mno-custom-insn
           -mcustom-fpu-cfg=name -mhal  -msmallc  -msys-crt0=name
           -msys-lib=name -march=arch  -mbmx  -mno-bmx  -mcdx  -mno-cdx

           Nvidia PTX Options -m64  -mmainkernel  -moptimize

           OpenRISC Options -mboard=name  -mnewlib  -mhard-mul  -mhard-div
           -msoft-mul  -msoft-div -msoft-float  -mhard-float  -mdouble-float
           -munordered-float -mcmov  -mror  -mrori  -msext  -msfimm  -mshftimm

           PDP-11 Options -mfpu  -msoft-float  -mac0  -mno-ac0  -m40  -m45  -m10
           -mint32  -mno-int16  -mint16  -mno-int32 -msplit  -munix-asm
           -mdec-asm  -mgnu-asm  -mlra

           picoChip Options -mae=ae_type  -mvliw-lookahead=N -msymbol-as-address
           -mno-inefficient-warnings

           PowerPC Options See RS/6000 and PowerPC Options.

           PRU Options -mmcu=mcu  -minrt  -mno-relax  -mloop -mabi=variant

           RISC-V Options -mbranch-cost=N-instruction -mplt  -mno-plt -mabi=ABI-
           string -mfdiv  -mno-fdiv -mdiv  -mno-div -march=ISA-string
           -mtune=processor-string -mpreferred-stack-boundary=num
           -msmall-data-limit=N-bytes -msave-restore  -mno-save-restore
           -mshorten-memrefs  -mno-shorten-memrefs -mstrict-align
           -mno-strict-align -mcmodel=medlow  -mcmodel=medany -mexplicit-relocs
           -mno-explicit-relocs -mrelax  -mno-relax -mriscv-attribute
           -mmo-riscv-attribute -malign-data=type -mbig-endian  -mlittle-endian
           +-mstack-protector-guard=guard -mstack-protector-guard-reg=reg
           +-mstack-protector-guard-offset=offset

           RL78 Options -msim  -mmul=none  -mmul=g13  -mmul=g14  -mallregs
           -mcpu=g10  -mcpu=g13  -mcpu=g14  -mg10  -mg13  -mg14 -m64bit-doubles
           -m32bit-doubles  -msave-mduc-in-interrupts

           RS/6000 and PowerPC Options -mcpu=cpu-type -mtune=cpu-type
           -mcmodel=code-model -mpowerpc64 -maltivec  -mno-altivec
           -mpowerpc-gpopt  -mno-powerpc-gpopt -mpowerpc-gfxopt
           -mno-powerpc-gfxopt -mmfcrf  -mno-mfcrf  -mpopcntb  -mno-popcntb
           -mpopcntd  -mno-popcntd -mfprnd  -mno-fprnd -mcmpb  -mno-cmpb
           -mhard-dfp  -mno-hard-dfp -mfull-toc   -mminimal-toc  -mno-fp-in-toc
           -mno-sum-in-toc -m64  -m32  -mxl-compat  -mno-xl-compat  -mpe
           -malign-power  -malign-natural -msoft-float  -mhard-float  -mmultiple
           -mno-multiple -mupdate  -mno-update -mavoid-indexed-addresses
           -mno-avoid-indexed-addresses -mfused-madd  -mno-fused-madd
           -mbit-align  -mno-bit-align -mstrict-align  -mno-strict-align
           -mrelocatable -mno-relocatable  -mrelocatable-lib
           -mno-relocatable-lib -mtoc  -mno-toc  -mlittle  -mlittle-endian
           -mbig  -mbig-endian -mdynamic-no-pic  -mswdiv  -msingle-pic-base
           -mprioritize-restricted-insns=priority
           -msched-costly-dep=dependence_type -minsert-sched-nops=scheme
           -mcall-aixdesc  -mcall-eabi  -mcall-freebsd -mcall-linux
           -mcall-netbsd  -mcall-openbsd -mcall-sysv  -mcall-sysv-eabi
           -mcall-sysv-noeabi -mtraceback=traceback_type -maix-struct-return
           -msvr4-struct-return -mabi=abi-type  -msecure-plt  -mbss-plt
           -mlongcall  -mno-longcall  -mpltseq  -mno-pltseq
           -mblock-move-inline-limit=num -mblock-compare-inline-limit=num
           -mblock-compare-inline-loop-limit=num -mno-block-ops-unaligned-vsx
           -mstring-compare-inline-limit=num -misel  -mno-isel -mvrsave
           -mno-vrsave -mmulhw  -mno-mulhw -mdlmzb  -mno-dlmzb -mprototype
           -mno-prototype -msim  -mmvme  -mads  -myellowknife  -memb  -msdata
           -msdata=opt  -mreadonly-in-sdata  -mvxworks  -G num -mrecip
           -mrecip=opt  -mno-recip  -mrecip-precision -mno-recip-precision
           -mveclibabi=type  -mfriz  -mno-friz -mpointers-to-nested-functions
           -mno-pointers-to-nested-functions -msave-toc-indirect
           -mno-save-toc-indirect -mpower8-fusion  -mno-mpower8-fusion
           -mpower8-vector  -mno-power8-vector -mcrypto  -mno-crypto  -mhtm
           -mno-htm -mquad-memory  -mno-quad-memory -mquad-memory-atomic
           -mno-quad-memory-atomic -mcompat-align-parm  -mno-compat-align-parm
           -mfloat128  -mno-float128  -mfloat128-hardware
           -mno-float128-hardware -mgnu-attribute  -mno-gnu-attribute
           -mstack-protector-guard=guard -mstack-protector-guard-reg=reg
           -mstack-protector-guard-offset=offset -mprefixed -mno-prefixed
           -mpcrel -mno-pcrel -mmma -mno-mmma

           RX Options -m64bit-doubles  -m32bit-doubles  -fpu  -nofpu -mcpu=
           -mbig-endian-data  -mlittle-endian-data -msmall-data -msim  -mno-sim
           -mas100-syntax  -mno-as100-syntax -mrelax -mmax-constant-size=
           -mint-register= -mpid -mallow-string-insns  -mno-allow-string-insns
           -mjsr -mno-warn-multiple-fast-interrupts -msave-acc-in-interrupts

           S/390 and zSeries Options -mtune=cpu-type  -march=cpu-type
           -mhard-float  -msoft-float  -mhard-dfp  -mno-hard-dfp
           -mlong-double-64  -mlong-double-128 -mbackchain  -mno-backchain
           -mpacked-stack  -mno-packed-stack -msmall-exec  -mno-small-exec
           -mmvcle  -mno-mvcle -m64  -m31  -mdebug  -mno-debug  -mesa  -mzarch
           -mhtm  -mvx  -mzvector -mtpf-trace  -mno-tpf-trace  -mtpf-trace-skip
           -mno-tpf-trace-skip -mfused-madd  -mno-fused-madd -mwarn-framesize
           -mwarn-dynamicstack  -mstack-size  -mstack-guard
           -mhotpatch=halfwords,halfwords

           Score Options -meb  -mel -mnhwloop -muls -mmac -mscore5  -mscore5u
           -mscore7  -mscore7d

           SH Options -m1  -m2  -m2e -m2a-nofpu  -m2a-single-only  -m2a-single
           -m2a -m3  -m3e -m4-nofpu  -m4-single-only  -m4-single  -m4 -m4a-nofpu
           -m4a-single-only  -m4a-single  -m4a  -m4al -mb  -ml  -mdalign
           -mrelax -mbigtable  -mfmovd  -mrenesas  -mno-renesas  -mnomacsave
           -mieee  -mno-ieee  -mbitops  -misize  -minline-ic_invalidate
           -mpadstruct -mprefergot  -musermode  -multcost=number  -mdiv=strategy
           -mdivsi3_libfunc=name  -mfixed-range=register-range
           -maccumulate-outgoing-args -matomic-model=atomic-model
           -mbranch-cost=num  -mzdcbranch  -mno-zdcbranch
           -mcbranch-force-delay-slot -mfused-madd  -mno-fused-madd  -mfsca
           -mno-fsca  -mfsrra  -mno-fsrra -mpretend-cmove  -mtas

           Solaris 2 Options -mclear-hwcap  -mno-clear-hwcap  -mimpure-text
           -mno-impure-text -pthreads

           SPARC Options -mcpu=cpu-type -mtune=cpu-type -mcmodel=code-model
           -mmemory-model=mem-model -m32  -m64  -mapp-regs  -mno-app-regs
           -mfaster-structs  -mno-faster-structs  -mflat  -mno-flat -mfpu
           -mno-fpu  -mhard-float  -msoft-float -mhard-quad-float
           -msoft-quad-float -mstack-bias  -mno-stack-bias -mstd-struct-return
           -mno-std-struct-return -munaligned-doubles  -mno-unaligned-doubles
           -muser-mode  -mno-user-mode -mv8plus  -mno-v8plus  -mvis  -mno-vis
           -mvis2  -mno-vis2  -mvis3  -mno-vis3 -mvis4  -mno-vis4  -mvis4b
           -mno-vis4b -mcbcond  -mno-cbcond  -mfmaf  -mno-fmaf  -mfsmuld
           -mno-fsmuld -mpopc  -mno-popc  -msubxc  -mno-subxc -mfix-at697f
           -mfix-ut699  -mfix-ut700  -mfix-gr712rc -mlra  -mno-lra

           System V Options -Qy  -Qn  -YP,paths  -Ym,dir

           TILE-Gx Options -mcpu=CPU  -m32  -m64  -mbig-endian  -mlittle-endian
           -mcmodel=code-model

           TILEPro Options -mcpu=cpu  -m32

           V850 Options -mlong-calls  -mno-long-calls  -mep  -mno-ep
           -mprolog-function  -mno-prolog-function  -mspace -mtda=n  -msda=n
           -mzda=n -mapp-regs  -mno-app-regs -mdisable-callt  -mno-disable-callt
           -mv850e2v3  -mv850e2  -mv850e1  -mv850es -mv850e  -mv850  -mv850e3v5
           -mloop -mrelax -mlong-jumps -msoft-float -mhard-float -mgcc-abi
           -mrh850-abi -mbig-switch

           VAX Options -mg  -mgnu  -munix

           Visium Options -mdebug  -msim  -mfpu  -mno-fpu  -mhard-float
           -msoft-float -mcpu=cpu-type  -mtune=cpu-type  -msv-mode  -muser-mode

           VMS Options -mvms-return-codes  -mdebug-main=prefix  -mmalloc64
           -mpointer-size=size

           VxWorks Options -mrtp  -non-static  -Bstatic  -Bdynamic -Xbind-lazy
           -Xbind-now

           x86 Options -mtune=cpu-type  -march=cpu-type -mtune-ctrl=feature-list
           -mdump-tune-features  -mno-default -mfpmath=unit -masm=dialect
           -mno-fancy-math-387 -mno-fp-ret-in-387  -m80387  -mhard-float
           -msoft-float -mno-wide-multiply  -mrtd  -malign-double
           -mpreferred-stack-boundary=num -mincoming-stack-boundary=num -mcld
           -mcx16  -msahf  -mmovbe  -mcrc32 -mrecip  -mrecip=opt -mvzeroupper
           -mprefer-avx128  -mprefer-vector-width=opt -mmmx  -msse  -msse2
           -msse3  -mssse3  -msse4.1  -msse4.2  -msse4  -mavx -mavx2  -mavx512f
           -mavx512pf  -mavx512er  -mavx512cd  -mavx512vl -mavx512bw  -mavx512dq
           -mavx512ifma  -mavx512vbmi  -msha  -maes -mpclmul  -mfsgsbase
           -mrdrnd  -mf16c  -mfma  -mpconfig  -mwbnoinvd -mptwrite
           -mprefetchwt1  -mclflushopt  -mclwb  -mxsavec  -mxsaves -msse4a
           -m3dnow  -m3dnowa  -mpopcnt  -mabm  -mbmi  -mtbm  -mfma4  -mxop -madx
           -mlzcnt  -mbmi2  -mfxsr  -mxsave  -mxsaveopt  -mrtm  -mhle  -mlwp
           -mmwaitx  -mclzero  -mpku  -mthreads  -mgfni  -mvaes  -mwaitpkg
           -mshstk -mmanual-endbr -mforce-indirect-call  -mavx512vbmi2
           -mavx512bf16 -menqcmd -mvpclmulqdq  -mavx512bitalg  -mmovdiri
           -mmovdir64b  -mavx512vpopcntdq -mavx5124fmaps  -mavx512vnni
           -mavx5124vnniw  -mprfchw  -mrdpid -mrdseed  -msgx
           -mavx512vp2intersect -mserialize -mtsxldtrk -mamx-tile  -mamx-int8
           -mamx-bf16 -muintr -mhreset -mavxvnni -mcldemote  -mms-bitfields
           -mno-align-stringops  -minline-all-stringops
           -minline-stringops-dynamically  -mstringop-strategy=alg -mkl -mwidekl
           -mmemcpy-strategy=strategy  -mmemset-strategy=strategy -mpush-args
           -maccumulate-outgoing-args  -m128bit-long-double -m96bit-long-double
           -mlong-double-64  -mlong-double-80  -mlong-double-128 -mregparm=num
           -msseregparm -mveclibabi=type  -mvect8-ret-in-mem -mpc32  -mpc64
           -mpc80  -mstackrealign -momit-leaf-frame-pointer  -mno-red-zone
           -mno-tls-direct-seg-refs -mcmodel=code-model  -mabi=name
           -maddress-mode=mode -m32  -m64  -mx32  -m16  -miamcu
           -mlarge-data-threshold=num -msse2avx  -mfentry  -mrecord-mcount
           -mnop-mcount  -m8bit-idiv -minstrument-return=type -mfentry-name=name
           -mfentry-section=name -mavx256-split-unaligned-load
           -mavx256-split-unaligned-store -malign-data=type
           -mstack-protector-guard=guard -mstack-protector-guard-reg=reg
           -mstack-protector-guard-offset=offset
           -mstack-protector-guard-symbol=symbol -mgeneral-regs-only
           -mcall-ms2sysv-xlogues -mindirect-branch=choice
           -mfunction-return=choice -mindirect-branch-register -mneeded

           x86 Windows Options -mconsole  -mcygwin  -mno-cygwin  -mdll
           -mnop-fun-dllimport  -mthread -municode  -mwin32  -mwindows
           -fno-set-stack-executable

           Xstormy16 Options -msim

           Xtensa Options -mconst16  -mno-const16 -mfused-madd  -mno-fused-madd
           -mforce-no-pic -mserialize-volatile  -mno-serialize-volatile
           -mtext-section-literals  -mno-text-section-literals -mauto-litpools
           -mno-auto-litpools -mtarget-align  -mno-target-align -mlongcalls
           -mno-longcalls -mabi=abi-type

           zSeries Options See S/390 and zSeries Options.

   Options Controlling the Kind of Output
       Compilation can involve up to four stages: preprocessing, compilation
       proper, assembly and linking, always in that order.  GCC is capable of
       preprocessing and compiling several files either into several assembler
       input files, or into one assembler input file; then each assembler input
       file produces an object file, and linking combines all the object files
       (those newly compiled, and those specified as input) into an executable
       file.

       For any given input file, the file name suffix determines what kind of
       compilation is done:

       file.c
           C source code that must be preprocessed.

       file.i
           C source code that should not be preprocessed.

       file.ii
           C++ source code that should not be preprocessed.

       file.m
           Objective-C source code.  Note that you must link with the libobjc
           library to make an Objective-C program work.

       file.mi
           Objective-C source code that should not be preprocessed.

       file.mm
       file.M
           Objective-C++ source code.  Note that you must link with the libobjc
           library to make an Objective-C++ program work.  Note that .M refers
           to a literal capital M.

       file.mii
           Objective-C++ source code that should not be preprocessed.

       file.h
           C, C++, Objective-C or Objective-C++ header file to be turned into a
           precompiled header (default), or C, C++ header file to be turned into
           an Ada spec (via the -fdump-ada-spec switch).

       file.cc
       file.cp
       file.cxx
       file.cpp
       file.CPP
       file.c++
       file.C
           C++ source code that must be preprocessed.  Note that in .cxx, the
           last two letters must both be literally x.  Likewise, .C refers to a
           literal capital C.

       file.mm
       file.M
           Objective-C++ source code that must be preprocessed.

       file.mii
           Objective-C++ source code that should not be preprocessed.

       file.hh
       file.H
       file.hp
       file.hxx
       file.hpp
       file.HPP
       file.h++
       file.tcc
           C++ header file to be turned into a precompiled header or Ada spec.

       file.f
       file.for
       file.ftn
           Fixed form Fortran source code that should not be preprocessed.

       file.F
       file.FOR
       file.fpp
       file.FPP
       file.FTN
           Fixed form Fortran source code that must be preprocessed (with the
           traditional preprocessor).

       file.f90
       file.f95
       file.f03
       file.f08
           Free form Fortran source code that should not be preprocessed.

       file.F90
       file.F95
       file.F03
       file.F08
           Free form Fortran source code that must be preprocessed (with the
           traditional preprocessor).

       file.go
           Go source code.

       file.brig
           BRIG files (binary representation of HSAIL).

       file.d
           D source code.

       file.di
           D interface file.

       file.dd
           D documentation code (Ddoc).

       file.ads
           Ada source code file that contains a library unit declaration (a
           declaration of a package, subprogram, or generic, or a generic
           instantiation), or a library unit renaming declaration (a package,
           generic, or subprogram renaming declaration).  Such files are also
           called specs.

       file.adb
           Ada source code file containing a library unit body (a subprogram or
           package body).  Such files are also called bodies.

       file.s
           Assembler code.

       file.S
       file.sx
           Assembler code that must be preprocessed.

       other
           An object file to be fed straight into linking.  Any file name with
           no recognized suffix is treated this way.

       You can specify the input language explicitly with the -x option:

       -x language
           Specify explicitly the language for the following input files (rather
           than letting the compiler choose a default based on the file name
           suffix).  This option applies to all following input files until the
           next -x option.  Possible values for language are:

                   c  c-header  cpp-output
                   c++  c++-header  c++-system-header c++-user-header c++-cpp-output
                   objective-c  objective-c-header  objective-c-cpp-output
                   objective-c++ objective-c++-header objective-c++-cpp-output
                   assembler  assembler-with-cpp
                   ada
                   d
                   f77  f77-cpp-input f95  f95-cpp-input
                   go
                   brig

       -x none
           Turn off any specification of a language, so that subsequent files
           are handled according to their file name suffixes (as they are if -x
           has not been used at all).

       If you only want some of the stages of compilation, you can use -x (or
       filename suffixes) to tell gcc where to start, and one of the options -c,
       -S, or -E to say where gcc is to stop.  Note that some combinations (for
       example, -x cpp-output -E) instruct gcc to do nothing at all.

       -c  Compile or assemble the source files, but do not link.  The linking
           stage simply is not done.  The ultimate output is in the form of an
           object file for each source file.

           By default, the object file name for a source file is made by
           replacing the suffix .c, .i, .s, etc., with .o.

           Unrecognized input files, not requiring compilation or assembly, are
           ignored.

       -S  Stop after the stage of compilation proper; do not assemble.  The
           output is in the form of an assembler code file for each non-
           assembler input file specified.

           By default, the assembler file name for a source file is made by
           replacing the suffix .c, .i, etc., with .s.

           Input files that don't require compilation are ignored.

       -E  Stop after the preprocessing stage; do not run the compiler proper.
           The output is in the form of preprocessed source code, which is sent
           to the standard output.

           Input files that don't require preprocessing are ignored.

       -o file
           Place the primary output in file file.  This applies to whatever sort
           of output is being produced, whether it be an executable file, an
           object file, an assembler file or preprocessed C code.

           If -o is not specified, the default is to put an executable file in
           a.out, the object file for source.suffix in source.o, its assembler
           file in source.s, a precompiled header file in source.suffix.gch, and
           all preprocessed C source on standard output.

           Though -o names only the primary output, it also affects the naming
           of auxiliary and dump outputs.  See the examples below.  Unless
           overridden, both auxiliary outputs and dump outputs are placed in the
           same directory as the primary output.  In auxiliary outputs, the
           suffix of the input file is replaced with that of the auxiliary
           output file type; in dump outputs, the suffix of the dump file is
           appended to the input file suffix.  In compilation commands, the base
           name of both auxiliary and dump outputs is that of the primary
           output; in compile and link commands, the primary output name, minus
           the executable suffix, is combined with the input file name.  If both
           share the same base name, disregarding the suffix, the result of the
           combination is that base name, otherwise, they are concatenated,
           separated by a dash.

                   gcc -c foo.c ...

           will use foo.o as the primary output, and place aux outputs and dumps
           next to it, e.g., aux file foo.dwo for -gsplit-dwarf, and dump file
           foo.c.???r.final for -fdump-rtl-final.

           If a non-linker output file is explicitly specified, aux and dump
           files by default take the same base name:

                   gcc -c foo.c -o dir/foobar.o ...

           will name aux outputs dir/foobar.* and dump outputs dir/foobar.c.*.

           A linker output will instead prefix aux and dump outputs:

                   gcc foo.c bar.c -o dir/foobar ...

           will generally name aux outputs dir/foobar-foo.* and
           dir/foobar-bar.*, and dump outputs dir/foobar-foo.c.* and
           dir/foobar-bar.c.*.

           The one exception to the above is when the executable shares the base
           name with the single input:

                   gcc foo.c -o dir/foo ...

           in which case aux outputs are named dir/foo.* and dump outputs named
           dir/foo.c.*.

           The location and the names of auxiliary and dump outputs can be
           adjusted by the options -dumpbase, -dumpbase-ext, -dumpdir,
           -save-temps=cwd, and -save-temps=obj.

       -dumpbase dumpbase
           This option sets the base name for auxiliary and dump output files.
           It does not affect the name of the primary output file.  Intermediate
           outputs, when preserved, are not regarded as primary outputs, but as
           auxiliary outputs:

                   gcc -save-temps -S foo.c

           saves the (no longer) temporary preprocessed file in foo.i, and then
           compiles to the (implied) output file foo.s, whereas:

                   gcc -save-temps -dumpbase save-foo -c foo.c

           preprocesses to in save-foo.i, compiles to save-foo.s (now an
           intermediate, thus auxiliary output), and then assembles to the
           (implied) output file foo.o.

           Absent this option, dump and aux files take their names from the
           input file, or from the (non-linker) output file, if one is
           explicitly specified: dump output files (e.g. those requested by
           -fdump-* options) with the input name suffix, and aux output files
           (those requested by other non-dump options, e.g. "-save-temps",
           "-gsplit-dwarf", "-fcallgraph-info") without it.

           Similar suffix differentiation of dump and aux outputs can be
           attained for explicitly-given -dumpbase basename.suf by also
           specifying -dumpbase-ext .suf.

           If dumpbase is explicitly specified with any directory component, any
           dumppfx specification (e.g. -dumpdir or -save-temps=*) is ignored,
           and instead of appending to it, dumpbase fully overrides it:

                   gcc foo.c -c -o dir/foo.o -dumpbase alt/foo \
                     -dumpdir pfx- -save-temps=cwd ...

           creates auxiliary and dump outputs named alt/foo.*, disregarding dir/
           in -o, the ./ prefix implied by -save-temps=cwd, and pfx- in
           -dumpdir.

           When -dumpbase is specified in a command that compiles multiple
           inputs, or that compiles and then links, it may be combined with
           dumppfx, as specified under -dumpdir.  Then, each input file is
           compiled using the combined dumppfx, and default values for dumpbase
           and auxdropsuf are computed for each input file:

                   gcc foo.c bar.c -c -dumpbase main ...

           creates foo.o and bar.o as primary outputs, and avoids overwriting
           the auxiliary and dump outputs by using the dumpbase as a prefix,
           creating auxiliary and dump outputs named main-foo.*  and main-bar.*.

           An empty string specified as dumpbase avoids the influence of the
           output basename in the naming of auxiliary and dump outputs during
           compilation, computing default values :

                   gcc -c foo.c -o dir/foobar.o -dumpbase " ...

           will name aux outputs dir/foo.* and dump outputs dir/foo.c.*.  Note
           how their basenames are taken from the input name, but the directory
           still defaults to that of the output.

           The empty-string dumpbase does not prevent the use of the output
           basename for outputs during linking:

                   gcc foo.c bar.c -o dir/foobar -dumpbase " -flto ...

           The compilation of the source files will name auxiliary outputs
           dir/foo.* and dir/bar.*, and dump outputs dir/foo.c.* and
           dir/bar.c.*.  LTO recompilation during linking will use dir/foobar.
           as the prefix for dumps and auxiliary files.

       -dumpbase-ext auxdropsuf
           When forming the name of an auxiliary (but not a dump) output file,
           drop trailing auxdropsuf from dumpbase before appending any suffixes.
           If not specified, this option defaults to the suffix of a default
           dumpbase, i.e., the suffix of the input file when -dumpbase is not
           present in the command line, or dumpbase is combined with dumppfx.

                   gcc foo.c -c -o dir/foo.o -dumpbase x-foo.c -dumpbase-ext .c ...

           creates dir/foo.o as the main output, and generates auxiliary outputs
           in dir/x-foo.*, taking the location of the primary output, and
           dropping the .c suffix from the dumpbase.  Dump outputs retain the
           suffix: dir/x-foo.c.*.

           This option is disregarded if it does not match the suffix of a
           specified dumpbase, except as an alternative to the executable suffix
           when appending the linker output base name to dumppfx, as specified
           below:

                   gcc foo.c bar.c -o main.out -dumpbase-ext .out ...

           creates main.out as the primary output, and avoids overwriting the
           auxiliary and dump outputs by using the executable name minus
           auxdropsuf as a prefix, creating auxiliary outputs named main-foo.*
           and main-bar.* and dump outputs named main-foo.c.* and main-bar.c.*.

       -dumpdir dumppfx
           When forming the name of an auxiliary or dump output file, use
           dumppfx as a prefix:

                   gcc -dumpdir pfx- -c foo.c ...

           creates foo.o as the primary output, and auxiliary outputs named
           pfx-foo.*, combining the given dumppfx with the default dumpbase
           derived from the default primary output, derived in turn from the
           input name.  Dump outputs also take the input name suffix:
           pfx-foo.c.*.

           If dumppfx is to be used as a directory name, it must end with a
           directory separator:

                   gcc -dumpdir dir/ -c foo.c -o obj/bar.o ...

           creates obj/bar.o as the primary output, and auxiliary outputs named
           dir/bar.*, combining the given dumppfx with the default dumpbase
           derived from the primary output name.  Dump outputs also take the
           input name suffix: dir/bar.c.*.

           It defaults to the location of the output file; options
           -save-temps=cwd and -save-temps=obj override this default, just like
           an explicit -dumpdir option.  In case multiple such options are
           given, the last one prevails:

                   gcc -dumpdir pfx- -c foo.c -save-temps=obj ...

           outputs foo.o, with auxiliary outputs named foo.* because
           -save-temps=* overrides the dumppfx given by the earlier -dumpdir
           option.  It does not matter that =obj is the default for -save-temps,
           nor that the output directory is implicitly the current directory.
           Dump outputs are named foo.c.*.

           When compiling from multiple input files, if -dumpbase is specified,
           dumpbase, minus a auxdropsuf suffix, and a dash are appended to (or
           override, if containing any directory components) an explicit or
           defaulted dumppfx, so that each of the multiple compilations gets
           differently-named aux and dump outputs.

                   gcc foo.c bar.c -c -dumpdir dir/pfx- -dumpbase main ...

           outputs auxiliary dumps to dir/pfx-main-foo.* and dir/pfx-main-bar.*,
           appending dumpbase- to dumppfx.  Dump outputs retain the input file
           suffix: dir/pfx-main-foo.c.*  and dir/pfx-main-bar.c.*, respectively.
           Contrast with the single-input compilation:

                   gcc foo.c -c -dumpdir dir/pfx- -dumpbase main ...

           that, applying -dumpbase to a single source, does not compute and
           append a separate dumpbase per input file.  Its auxiliary and dump
           outputs go in dir/pfx-main.*.

           When compiling and then linking from multiple input files, a
           defaulted or explicitly specified dumppfx also undergoes the
           dumpbase- transformation above (e.g. the compilation of foo.c and
           bar.c above, but without -c).  If neither -dumpdir nor -dumpbase are
           given, the linker output base name, minus auxdropsuf, if specified,
           or the executable suffix otherwise, plus a dash is appended to the
           default dumppfx instead.  Note, however, that unlike earlier cases of
           linking:

                   gcc foo.c bar.c -dumpdir dir/pfx- -o main ...

           does not append the output name main to dumppfx, because -dumpdir is
           explicitly specified.  The goal is that the explicitly-specified
           dumppfx may contain the specified output name as part of the prefix,
           if desired; only an explicitly-specified -dumpbase would be combined
           with it, in order to avoid simply discarding a meaningful option.

           When compiling and then linking from a single input file, the linker
           output base name will only be appended to the default dumppfx as
           above if it does not share the base name with the single input file
           name.  This has been covered in single-input linking cases above, but
           not with an explicit -dumpdir that inhibits the combination, even if
           overridden by -save-temps=*:

                   gcc foo.c -dumpdir alt/pfx- -o dir/main.exe -save-temps=cwd ...

           Auxiliary outputs are named foo.*, and dump outputs foo.c.*, in the
           current working directory as ultimately requested by -save-temps=cwd.

           Summing it all up for an intuitive though slightly imprecise data
           flow: the primary output name is broken into a directory part and a
           basename part; dumppfx is set to the former, unless overridden by
           -dumpdir or -save-temps=*, and dumpbase is set to the latter, unless
           overriden by -dumpbase.  If there are multiple inputs or linking,
           this dumpbase may be combined with dumppfx and taken from each input
           file.  Auxiliary output names for each input are formed by combining
           dumppfx, dumpbase minus suffix, and the auxiliary output suffix; dump
           output names are only different in that the suffix from dumpbase is
           retained.

           When it comes to auxiliary and dump outputs created during LTO
           recompilation, a combination of dumppfx and dumpbase, as given or as
           derived from the linker output name but not from inputs, even in
           cases in which this combination would not otherwise be used as such,
           is passed down with a trailing period replacing the compiler-added
           dash, if any, as a -dumpdir option to lto-wrapper; being involved in
           linking, this program does not normally get any -dumpbase and
           -dumpbase-ext, and it ignores them.

           When running sub-compilers, lto-wrapper appends LTO stage names to
           the received dumppfx, ensures it contains a directory component so
           that it overrides any -dumpdir, and passes that as -dumpbase to sub-
           compilers.

       -v  Print (on standard error output) the commands executed to run the
           stages of compilation.  Also print the version number of the compiler
           driver program and of the preprocessor and the compiler proper.

       -###
           Like -v except the commands are not executed and arguments are quoted
           unless they contain only alphanumeric characters or "./-_".  This is
           useful for shell scripts to capture the driver-generated command
           lines.

       --help
           Print (on the standard output) a description of the command-line
           options understood by gcc.  If the -v option is also specified then
           --help is also passed on to the various processes invoked by gcc, so
           that they can display the command-line options they accept.  If the
           -Wextra option has also been specified (prior to the --help option),
           then command-line options that have no documentation associated with
           them are also displayed.

       --target-help
           Print (on the standard output) a description of target-specific
           command-line options for each tool.  For some targets extra target-
           specific information may also be printed.

       --help={class|[^]qualifier}[,...]
           Print (on the standard output) a description of the command-line
           options understood by the compiler that fit into all specified
           classes and qualifiers.  These are the supported classes:

           optimizers
               Display all of the optimization options supported by the
               compiler.

           warnings
               Display all of the options controlling warning messages produced
               by the compiler.

           target
               Display target-specific options.  Unlike the --target-help option
               however, target-specific options of the linker and assembler are
               not displayed.  This is because those tools do not currently
               support the extended --help= syntax.

           params
               Display the values recognized by the --param option.

           language
               Display the options supported for language, where language is the
               name of one of the languages supported in this version of GCC.
               If an option is supported by all languages, one needs to select
               common class.

           common
               Display the options that are common to all languages.

           These are the supported qualifiers:

           undocumented
               Display only those options that are undocumented.

           joined
               Display options taking an argument that appears after an equal
               sign in the same continuous piece of text, such as:
               --help=target.

           separate
               Display options taking an argument that appears as a separate
               word following the original option, such as: -o output-file.

           Thus for example to display all the undocumented target-specific
           switches supported by the compiler, use:

                   --help=target,undocumented

           The sense of a qualifier can be inverted by prefixing it with the ^
           character, so for example to display all binary warning options
           (i.e., ones that are either on or off and that do not take an
           argument) that have a description, use:

                   --help=warnings,^joined,^undocumented

           The argument to --help= should not consist solely of inverted
           qualifiers.

           Combining several classes is possible, although this usually
           restricts the output so much that there is nothing to display.  One
           case where it does work, however, is when one of the classes is
           target.  For example, to display all the target-specific optimization
           options, use:

                   --help=target,optimizers

           The --help= option can be repeated on the command line.  Each
           successive use displays its requested class of options, skipping
           those that have already been displayed.  If --help is also specified
           anywhere on the command line then this takes precedence over any
           --help= option.

           If the -Q option appears on the command line before the --help=
           option, then the descriptive text displayed by --help= is changed.
           Instead of describing the displayed options, an indication is given
           as to whether the option is enabled, disabled or set to a specific
           value (assuming that the compiler knows this at the point where the
           --help= option is used).

           Here is a truncated example from the ARM port of gcc:

                     % gcc -Q -mabi=2 --help=target -c
                     The following options are target specific:
                     -mabi=                                2
                     -mabort-on-noreturn                   [disabled]
                     -mapcs                                [disabled]

           The output is sensitive to the effects of previous command-line
           options, so for example it is possible to find out which
           optimizations are enabled at -O2 by using:

                   -Q -O2 --help=optimizers

           Alternatively you can discover which binary optimizations are enabled
           by -O3 by using:

                   gcc -c -Q -O3 --help=optimizers > /tmp/O3-opts
                   gcc -c -Q -O2 --help=optimizers > /tmp/O2-opts
                   diff /tmp/O2-opts /tmp/O3-opts | grep enabled

       --version
           Display the version number and copyrights of the invoked GCC.

       -pass-exit-codes
           Normally the gcc program exits with the code of 1 if any phase of the
           compiler returns a non-success return code.  If you specify
           -pass-exit-codes, the gcc program instead returns with the
           numerically highest error produced by any phase returning an error
           indication.  The C, C++, and Fortran front ends return 4 if an
           internal compiler error is encountered.

       -pipe
           Use pipes rather than temporary files for communication between the
           various stages of compilation.  This fails to work on some systems
           where the assembler is unable to read from a pipe; but the GNU
           assembler has no trouble.

       -specs=file
           Process file after the compiler reads in the standard specs file, in
           order to override the defaults which the gcc driver program uses when
           determining what switches to pass to cc1, cc1plus, as, ld, etc.  More
           than one -specs=file can be specified on the command line, and they
           are processed in order, from left to right.

       -wrapper
           Invoke all subcommands under a wrapper program.  The name of the
           wrapper program and its parameters are passed as a comma separated
           list.

                   gcc -c t.c -wrapper gdb,--args

           This invokes all subprograms of gcc under gdb --args, thus the
           invocation of cc1 is gdb --args cc1 ....

       -ffile-prefix-map=old=new
           When compiling files residing in directory old, record any references
           to them in the result of the compilation as if the files resided in
           directory new instead.  Specifying this option is equivalent to
           specifying all the individual -f*-prefix-map options.  This can be
           used to make reproducible builds that are location independent.  See
           also -fmacro-prefix-map and -fdebug-prefix-map.

       -fplugin=name.so
           Load the plugin code in file name.so, assumed to be a shared object
           to be dlopen'd by the compiler.  The base name of the shared object
           file is used to identify the plugin for the purposes of argument
           parsing (See -fplugin-arg-name-key=value below).  Each plugin should
           define the callback functions specified in the Plugins API.

       -fplugin-arg-name-key=value
           Define an argument called key with a value of value for the plugin
           called name.

       -fdump-ada-spec[-slim]
           For C and C++ source and include files, generate corresponding Ada
           specs.

       -fada-spec-parent=unit
           In conjunction with -fdump-ada-spec[-slim] above, generate Ada specs
           as child units of parent unit.

       -fdump-go-spec=file
           For input files in any language, generate corresponding Go
           declarations in file.  This generates Go "const", "type", "var", and
           "func" declarations which may be a useful way to start writing a Go
           interface to code written in some other language.

       @file
           Read command-line options from file.  The options read are inserted
           in place of the original @file option.  If file does not exist, or
           cannot be read, then the option will be treated literally, and not
           removed.

           Options in file are separated by whitespace.  A whitespace character
           may be included in an option by surrounding the entire option in
           either single or double quotes.  Any character (including a
           backslash) may be included by prefixing the character to be included
           with a backslash.  The file may itself contain additional @file
           options; any such options will be processed recursively.

   Compiling C++ Programs
       C++ source files conventionally use one of the suffixes .C, .cc, .cpp,
       .CPP, .c++, .cp, or .cxx; C++ header files often use .hh, .hpp, .H, or
       (for shared template code) .tcc; and preprocessed C++ files use the
       suffix .ii.  GCC recognizes files with these names and compiles them as
       C++ programs even if you call the compiler the same way as for compiling
       C programs (usually with the name gcc).

       However, the use of gcc does not add the C++ library.  g++ is a program
       that calls GCC and automatically specifies linking against the C++
       library.  It treats .c, .h and .i files as C++ source files instead of C
       source files unless -x is used.  This program is also useful when
       precompiling a C header file with a .h extension for use in C++
       compilations.  On many systems, g++ is also installed with the name c++.

       When you compile C++ programs, you may specify many of the same command-
       line options that you use for compiling programs in any language; or
       command-line options meaningful for C and related languages; or options
       that are meaningful only for C++ programs.

   Options Controlling C Dialect
       The following options control the dialect of C (or languages derived from
       C, such as C++, Objective-C and Objective-C++) that the compiler accepts:

       -ansi
           In C mode, this is equivalent to -std=c90. In C++ mode, it is
           equivalent to -std=c++98.

           This turns off certain features of GCC that are incompatible with ISO
           C90 (when compiling C code), or of standard C++ (when compiling C++
           code), such as the "asm" and "typeof" keywords, and predefined macros
           such as "unix" and "vax" that identify the type of system you are
           using.  It also enables the undesirable and rarely used ISO trigraph
           feature.  For the C compiler, it disables recognition of C++ style //
           comments as well as the "inline" keyword.

           The alternate keywords "__asm__", "__extension__", "__inline__" and
           "__typeof__" continue to work despite -ansi.  You would not want to
           use them in an ISO C program, of course, but it is useful to put them
           in header files that might be included in compilations done with
           -ansi.  Alternate predefined macros such as "__unix__" and "__vax__"
           are also available, with or without -ansi.

           The -ansi option does not cause non-ISO programs to be rejected
           gratuitously.  For that, -Wpedantic is required in addition to -ansi.

           The macro "__STRICT_ANSI__" is predefined when the -ansi option is
           used.  Some header files may notice this macro and refrain from
           declaring certain functions or defining certain macros that the ISO
           standard doesn't call for; this is to avoid interfering with any
           programs that might use these names for other things.

           Functions that are normally built in but do not have semantics
           defined by ISO C (such as "alloca" and "ffs") are not built-in
           functions when -ansi is used.

       -std=
           Determine the language standard.   This option is currently only
           supported when compiling C or C++.

           The compiler can accept several base standards, such as c90 or c++98,
           and GNU dialects of those standards, such as gnu90 or gnu++98.  When
           a base standard is specified, the compiler accepts all programs
           following that standard plus those using GNU extensions that do not
           contradict it.  For example, -std=c90 turns off certain features of
           GCC that are incompatible with ISO C90, such as the "asm" and
           "typeof" keywords, but not other GNU extensions that do not have a
           meaning in ISO C90, such as omitting the middle term of a "?:"
           expression. On the other hand, when a GNU dialect of a standard is
           specified, all features supported by the compiler are enabled, even
           when those features change the meaning of the base standard.  As a
           result, some strict-conforming programs may be rejected.  The
           particular standard is used by -Wpedantic to identify which features
           are GNU extensions given that version of the standard. For example
           -std=gnu90 -Wpedantic warns about C++ style // comments, while
           -std=gnu99 -Wpedantic does not.

           A value for this option must be provided; possible values are

           c90
           c89
           iso9899:1990
               Support all ISO C90 programs (certain GNU extensions that
               conflict with ISO C90 are disabled). Same as -ansi for C code.

           iso9899:199409
               ISO C90 as modified in amendment 1.

           c99
           c9x
           iso9899:1999
           iso9899:199x
               ISO C99.  This standard is substantially completely supported,
               modulo bugs and floating-point issues (mainly but not entirely
               relating to optional C99 features from Annexes F and G).  See
               <http://gcc.gnu.org/c99status.html> for more information.  The
               names c9x and iso9899:199x are deprecated.

           c11
           c1x
           iso9899:2011
               ISO C11, the 2011 revision of the ISO C standard.  This standard
               is substantially completely supported, modulo bugs, floating-
               point issues (mainly but not entirely relating to optional C11
               features from Annexes F and G) and the optional Annexes K
               (Bounds-checking interfaces) and L (Analyzability).  The name c1x
               is deprecated.

           c17
           c18
           iso9899:2017
           iso9899:2018
               ISO C17, the 2017 revision of the ISO C standard (published in
               2018).  This standard is same as C11 except for corrections of
               defects (all of which are also applied with -std=c11) and a new
               value of "__STDC_VERSION__", and so is supported to the same
               extent as C11.

           c2x The next version of the ISO C standard, still under development.
               The support for this version is experimental and incomplete.

           gnu90
           gnu89
               GNU dialect of ISO C90 (including some C99 features).

           gnu99
           gnu9x
               GNU dialect of ISO C99.  The name gnu9x is deprecated.

           gnu11
           gnu1x
               GNU dialect of ISO C11.  The name gnu1x is deprecated.

           gnu17
           gnu18
               GNU dialect of ISO C17.  This is the default for C code.

           gnu2x
               The next version of the ISO C standard, still under development,
               plus GNU extensions.  The support for this version is
               experimental and incomplete.

           c++98
           c++03
               The 1998 ISO C++ standard plus the 2003 technical corrigendum and
               some additional defect reports. Same as -ansi for C++ code.

           gnu++98
           gnu++03
               GNU dialect of -std=c++98.

           c++11
           c++0x
               The 2011 ISO C++ standard plus amendments.  The name c++0x is
               deprecated.

           gnu++11
           gnu++0x
               GNU dialect of -std=c++11.  The name gnu++0x is deprecated.

           c++14
           c++1y
               The 2014 ISO C++ standard plus amendments.  The name c++1y is
               deprecated.

           gnu++14
           gnu++1y
               GNU dialect of -std=c++14.  The name gnu++1y is deprecated.

           c++17
           c++1z
               The 2017 ISO C++ standard plus amendments.  The name c++1z is
               deprecated.

           gnu++17
           gnu++1z
               GNU dialect of -std=c++17.  This is the default for C++ code.
               The name gnu++1z is deprecated.

           c++20
           c++2a
               The 2020 ISO C++ standard plus amendments.  Support is
               experimental, and could change in incompatible ways in future
               releases.  The name c++2a is deprecated.

           gnu++20
           gnu++2a
               GNU dialect of -std=c++20.  Support is experimental, and could
               change in incompatible ways in future releases.  The name gnu++2a
               is deprecated.

           c++2b
           c++23
               The next revision of the ISO C++ standard, planned for 2023.
               Support is highly experimental, and will almost certainly change
               in incompatible ways in future releases.

           gnu++2b
           gnu++23
               GNU dialect of -std=c++2b.  Support is highly experimental, and
               will almost certainly change in incompatible ways in future
               releases.

       -fgnu89-inline
           The option -fgnu89-inline tells GCC to use the traditional GNU
           semantics for "inline" functions when in C99 mode.

           Using this option is roughly equivalent to adding the "gnu_inline"
           function attribute to all inline functions.

           The option -fno-gnu89-inline explicitly tells GCC to use the C99
           semantics for "inline" when in C99 or gnu99 mode (i.e., it specifies
           the default behavior).  This option is not supported in -std=c90 or
           -std=gnu90 mode.

           The preprocessor macros "__GNUC_GNU_INLINE__" and
           "__GNUC_STDC_INLINE__" may be used to check which semantics are in
           effect for "inline" functions.

       -fpermitted-flt-eval-methods=style
           ISO/IEC TS 18661-3 defines new permissible values for
           "FLT_EVAL_METHOD" that indicate that operations and constants with a
           semantic type that is an interchange or extended format should be
           evaluated to the precision and range of that type.  These new values
           are a superset of those permitted under C99/C11, which does not
           specify the meaning of other positive values of "FLT_EVAL_METHOD".
           As such, code conforming to C11 may not have been written expecting
           the possibility of the new values.

           -fpermitted-flt-eval-methods specifies whether the compiler should
           allow only the values of "FLT_EVAL_METHOD" specified in C99/C11, or
           the extended set of values specified in ISO/IEC TS 18661-3.

           style is either "c11" or "ts-18661-3" as appropriate.

           The default when in a standards compliant mode (-std=c11 or similar)
           is -fpermitted-flt-eval-methods=c11.  The default when in a GNU
           dialect (-std=gnu11 or similar) is
           -fpermitted-flt-eval-methods=ts-18661-3.

       -aux-info filename
           Output to the given filename prototyped declarations for all
           functions declared and/or defined in a translation unit, including
           those in header files.  This option is silently ignored in any
           language other than C.

           Besides declarations, the file indicates, in comments, the origin of
           each declaration (source file and line), whether the declaration was
           implicit, prototyped or unprototyped (I, N for new or O for old,
           respectively, in the first character after the line number and the
           colon), and whether it came from a declaration or a definition (C or
           F, respectively, in the following character).  In the case of
           function definitions, a K&R-style list of arguments followed by their
           declarations is also provided, inside comments, after the
           declaration.

       -fallow-parameterless-variadic-functions
           Accept variadic functions without named parameters.

           Although it is possible to define such a function, this is not very
           useful as it is not possible to read the arguments.  This is only
           supported for C as this construct is allowed by C++.

       -fno-asm
           Do not recognize "asm", "inline" or "typeof" as a keyword, so that
           code can use these words as identifiers.  You can use the keywords
           "__asm__", "__inline__" and "__typeof__" instead.  -ansi implies
           -fno-asm.

           In C++, this switch only affects the "typeof" keyword, since "asm"
           and "inline" are standard keywords.  You may want to use the
           -fno-gnu-keywords flag instead, which has the same effect.  In C99
           mode (-std=c99 or -std=gnu99), this switch only affects the "asm" and
           "typeof" keywords, since "inline" is a standard keyword in ISO C99.

       -fno-builtin
       -fno-builtin-function
           Don't recognize built-in functions that do not begin with __builtin_
           as prefix.

           GCC normally generates special code to handle certain built-in
           functions more efficiently; for instance, calls to "alloca" may
           become single instructions which adjust the stack directly, and calls
           to "memcpy" may become inline copy loops.  The resulting code is
           often both smaller and faster, but since the function calls no longer
           appear as such, you cannot set a breakpoint on those calls, nor can
           you change the behavior of the functions by linking with a different
           library.  In addition, when a function is recognized as a built-in
           function, GCC may use information about that function to warn about
           problems with calls to that function, or to generate more efficient
           code, even if the resulting code still contains calls to that
           function.  For example, warnings are given with -Wformat for bad
           calls to "printf" when "printf" is built in and "strlen" is known not
           to modify global memory.

           With the -fno-builtin-function option only the built-in function
           function is disabled.  function must not begin with __builtin_.  If a
           function is named that is not built-in in this version of GCC, this
           option is ignored.  There is no corresponding -fbuiltin-function
           option; if you wish to enable built-in functions selectively when
           using -fno-builtin or -ffreestanding, you may define macros such as:

                   #define abs(n)          __builtin_abs ((n))
                   #define strcpy(d, s)    __builtin_strcpy ((d), (s))

       -fgimple
           Enable parsing of function definitions marked with "__GIMPLE".  This
           is an experimental feature that allows unit testing of GIMPLE passes.

       -fhosted
           Assert that compilation targets a hosted environment.  This implies
           -fbuiltin.  A hosted environment is one in which the entire standard
           library is available, and in which "main" has a return type of "int".
           Examples are nearly everything except a kernel.  This is equivalent
           to -fno-freestanding.

       -ffreestanding
           Assert that compilation targets a freestanding environment.  This
           implies -fno-builtin.  A freestanding environment is one in which the
           standard library may not exist, and program startup may not
           necessarily be at "main".  The most obvious example is an OS kernel.
           This is equivalent to -fno-hosted.

       -fopenacc
           Enable handling of OpenACC directives "#pragma acc" in C/C++ and
           "!$acc" in Fortran.  When -fopenacc is specified, the compiler
           generates accelerated code according to the OpenACC Application
           Programming Interface v2.6 <https://www.openacc.org>.  This option
           implies -pthread, and thus is only supported on targets that have
           support for -pthread.

       -fopenacc-dim=geom
           Specify default compute dimensions for parallel offload regions that
           do not explicitly specify.  The geom value is a triple of
           ':'-separated sizes, in order 'gang', 'worker' and, 'vector'.  A size
           can be omitted, to use a target-specific default value.

       -fopenmp
           Enable handling of OpenMP directives "#pragma omp" in C/C++ and
           "!$omp" in Fortran.  When -fopenmp is specified, the compiler
           generates parallel code according to the OpenMP Application Program
           Interface v4.5 <https://www.openmp.org>.  This option implies
           -pthread, and thus is only supported on targets that have support for
           -pthread. -fopenmp implies -fopenmp-simd.

       -fopenmp-simd
           Enable handling of OpenMP's SIMD directives with "#pragma omp" in
           C/C++ and "!$omp" in Fortran. Other OpenMP directives are ignored.

       -fgnu-tm
           When the option -fgnu-tm is specified, the compiler generates code
           for the Linux variant of Intel's current Transactional Memory ABI
           specification document (Revision 1.1, May 6 2009).  This is an
           experimental feature whose interface may change in future versions of
           GCC, as the official specification changes.  Please note that not all
           architectures are supported for this feature.

           For more information on GCC's support for transactional memory,

           Note that the transactional memory feature is not supported with non-
           call exceptions (-fnon-call-exceptions).

       -fms-extensions
           Accept some non-standard constructs used in Microsoft header files.

           In C++ code, this allows member names in structures to be similar to
           previous types declarations.

                   typedef int UOW;
                   struct ABC {
                     UOW UOW;
                   };

           Some cases of unnamed fields in structures and unions are only
           accepted with this option.

           Note that this option is off for all targets except for x86 targets
           using ms-abi.

       -fplan9-extensions
           Accept some non-standard constructs used in Plan 9 code.

           This enables -fms-extensions, permits passing pointers to structures
           with anonymous fields to functions that expect pointers to elements
           of the type of the field, and permits referring to anonymous fields
           declared using a typedef.    This is only supported for C, not C++.

       -fcond-mismatch
           Allow conditional expressions with mismatched types in the second and
           third arguments.  The value of such an expression is void.  This
           option is not supported for C++.

       -flax-vector-conversions
           Allow implicit conversions between vectors with differing numbers of
           elements and/or incompatible element types.  This option should not
           be used for new code.

       -funsigned-char
           Let the type "char" be unsigned, like "unsigned char".

           Each kind of machine has a default for what "char" should be.  It is
           either like "unsigned char" by default or like "signed char" by
           default.

           Ideally, a portable program should always use "signed char" or
           "unsigned char" when it depends on the signedness of an object.  But
           many programs have been written to use plain "char" and expect it to
           be signed, or expect it to be unsigned, depending on the machines
           they were written for.  This option, and its inverse, let you make
           such a program work with the opposite default.

           The type "char" is always a distinct type from each of "signed char"
           or "unsigned char", even though its behavior is always just like one
           of those two.

       -fsigned-char
           Let the type "char" be signed, like "signed char".

           Note that this is equivalent to -fno-unsigned-char, which is the
           negative form of -funsigned-char.  Likewise, the option
           -fno-signed-char is equivalent to -funsigned-char.

       -fsigned-bitfields
       -funsigned-bitfields
       -fno-signed-bitfields
       -fno-unsigned-bitfields
           These options control whether a bit-field is signed or unsigned, when
           the declaration does not use either "signed" or "unsigned".  By
           default, such a bit-field is signed, because this is consistent: the
           basic integer types such as "int" are signed types.

       -fsso-struct=endianness
           Set the default scalar storage order of structures and unions to the
           specified endianness.  The accepted values are big-endian, little-
           endian and native for the native endianness of the target (the
           default).  This option is not supported for C++.

           Warning: the -fsso-struct switch causes GCC to generate code that is
           not binary compatible with code generated without it if the specified
           endianness is not the native endianness of the target.

   Options Controlling C++ Dialect
       This section describes the command-line options that are only meaningful
       for C++ programs.  You can also use most of the GNU compiler options
       regardless of what language your program is in.  For example, you might
       compile a file firstClass.C like this:

               g++ -g -fstrict-enums -O -c firstClass.C

       In this example, only -fstrict-enums is an option meant only for C++
       programs; you can use the other options with any language supported by
       GCC.

       Some options for compiling C programs, such as -std, are also relevant
       for C++ programs.

       Here is a list of options that are only for compiling C++ programs:

       -fabi-version=n
           Use version n of the C++ ABI.  The default is version 0.

           Version 0 refers to the version conforming most closely to the C++
           ABI specification.  Therefore, the ABI obtained using version 0 will
           change in different versions of G++ as ABI bugs are fixed.

           Version 1 is the version of the C++ ABI that first appeared in G++
           3.2.

           Version 2 is the version of the C++ ABI that first appeared in G++
           3.4, and was the default through G++ 4.9.

           Version 3 corrects an error in mangling a constant address as a
           template argument.

           Version 4, which first appeared in G++ 4.5, implements a standard
           mangling for vector types.

           Version 5, which first appeared in G++ 4.6, corrects the mangling of
           attribute const/volatile on function pointer types, decltype of a
           plain decl, and use of a function parameter in the declaration of
           another parameter.

           Version 6, which first appeared in G++ 4.7, corrects the promotion
           behavior of C++11 scoped enums and the mangling of template argument
           packs, const/static_cast, prefix ++ and --, and a class scope
           function used as a template argument.

           Version 7, which first appeared in G++ 4.8, that treats nullptr_t as
           a builtin type and corrects the mangling of lambdas in default
           argument scope.

           Version 8, which first appeared in G++ 4.9, corrects the substitution
           behavior of function types with function-cv-qualifiers.

           Version 9, which first appeared in G++ 5.2, corrects the alignment of
           "nullptr_t".

           Version 10, which first appeared in G++ 6.1, adds mangling of
           attributes that affect type identity, such as ia32 calling convention
           attributes (e.g. stdcall).

           Version 11, which first appeared in G++ 7, corrects the mangling of
           sizeof... expressions and operator names.  For multiple entities with
           the same name within a function, that are declared in different
           scopes, the mangling now changes starting with the twelfth
           occurrence.  It also implies -fnew-inheriting-ctors.

           Version 12, which first appeared in G++ 8, corrects the calling
           conventions for empty classes on the x86_64 target and for classes
           with only deleted copy/move constructors.  It accidentally changes
           the calling convention for classes with a deleted copy constructor
           and a trivial move constructor.

           Version 13, which first appeared in G++ 8.2, fixes the accidental
           change in version 12.

           Version 14, which first appeared in G++ 10, corrects the mangling of
           the nullptr expression.

           Version 15, which first appeared in G++ 11, changes the mangling of
           "__alignof__" to be distinct from that of "alignof", and dependent
           operator names.

           See also -Wabi.

       -fabi-compat-version=n
           On targets that support strong aliases, G++ works around mangling
           changes by creating an alias with the correct mangled name when
           defining a symbol with an incorrect mangled name.  This switch
           specifies which ABI version to use for the alias.

           With -fabi-version=0 (the default), this defaults to 11 (GCC 7
           compatibility).  If another ABI version is explicitly selected, this
           defaults to 0.  For compatibility with GCC versions 3.2 through 4.9,
           use -fabi-compat-version=2.

           If this option is not provided but -Wabi=n is, that version is used
           for compatibility aliases.  If this option is provided along with
           -Wabi (without the version), the version from this option is used for
           the warning.

       -fno-access-control
           Turn off all access checking.  This switch is mainly useful for
           working around bugs in the access control code.

       -faligned-new
           Enable support for C++17 "new" of types that require more alignment
           than "void* ::operator new(std::size_t)" provides.  A numeric
           argument such as "-faligned-new=32" can be used to specify how much
           alignment (in bytes) is provided by that function, but few users will
           need to override the default of "alignof(std::max_align_t)".

           This flag is enabled by default for -std=c++17.

       -fchar8_t
       -fno-char8_t
           Enable support for "char8_t" as adopted for C++20.  This includes the
           addition of a new "char8_t" fundamental type, changes to the types of
           UTF-8 string and character literals, new signatures for user-defined
           literals, associated standard library updates, and new
           "__cpp_char8_t" and "__cpp_lib_char8_t" feature test macros.

           This option enables functions to be overloaded for ordinary and UTF-8
           strings:

                   int f(const char *);    // #1
                   int f(const char8_t *); // #2
                   int v1 = f("text");     // Calls #1
                   int v2 = f(u8"text");   // Calls #2

           and introduces new signatures for user-defined literals:

                   int operator""_udl1(char8_t);
                   int v3 = u8'x'_udl1;
                   int operator""_udl2(const char8_t*, std::size_t);
                   int v4 = u8"text"_udl2;
                   template<typename T, T...> int operator""_udl3();
                   int v5 = u8"text"_udl3;

           The change to the types of UTF-8 string and character literals
           introduces incompatibilities with ISO C++11 and later standards.  For
           example, the following code is well-formed under ISO C++11, but is
           ill-formed when -fchar8_t is specified.

                   char ca[] = u8"xx";     // error: char-array initialized from wide
                                           //        string
                   const char *cp = u8"xx";// error: invalid conversion from
                                           //        `const char8_t*' to `const char*'
                   int f(const char*);
                   auto v = f(u8"xx");     // error: invalid conversion from
                                           //        `const char8_t*' to `const char*'
                   std::string s{u8"xx"};  // error: no matching function for call to
                                           //        `std::basic_string<char>::basic_string()'
                   using namespace std::literals;
                   s = u8"xx"s;            // error: conversion from
                                           //        `basic_string<char8_t>' to non-scalar
                                           //        type `basic_string<char>' requested

       -fcheck-new
           Check that the pointer returned by "operator new" is non-null before
           attempting to modify the storage allocated.  This check is normally
           unnecessary because the C++ standard specifies that "operator new"
           only returns 0 if it is declared "throw()", in which case the
           compiler always checks the return value even without this option.  In
           all other cases, when "operator new" has a non-empty exception
           specification, memory exhaustion is signalled by throwing
           "std::bad_alloc".  See also new (nothrow).

       -fconcepts
       -fconcepts-ts
           Below -std=c++20, -fconcepts enables support for the C++ Extensions
           for Concepts Technical Specification, ISO 19217 (2015).

           With -std=c++20 and above, Concepts are part of the language
           standard, so -fconcepts defaults to on.  But the standard
           specification of Concepts differs significantly from the TS, so some
           constructs that were allowed in the TS but didn't make it into the
           standard can still be enabled by -fconcepts-ts.

       -fconstexpr-depth=n
           Set the maximum nested evaluation depth for C++11 constexpr functions
           to n.  A limit is needed to detect endless recursion during constant
           expression evaluation.  The minimum specified by the standard is 512.

       -fconstexpr-cache-depth=n
           Set the maximum level of nested evaluation depth for C++11 constexpr
           functions that will be cached to n.  This is a heuristic that trades
           off compilation speed (when the cache avoids repeated calculations)
           against memory consumption (when the cache grows very large from
           highly recursive evaluations).  The default is 8.  Very few users are
           likely to want to adjust it, but if your code does heavy constexpr
           calculations you might want to experiment to find which value works
           best for you.

       -fconstexpr-loop-limit=n
           Set the maximum number of iterations for a loop in C++14 constexpr
           functions to n.  A limit is needed to detect infinite loops during
           constant expression evaluation.  The default is 262144 (1<<18).

       -fconstexpr-ops-limit=n
           Set the maximum number of operations during a single constexpr
           evaluation.  Even when number of iterations of a single loop is
           limited with the above limit, if there are several nested loops and
           each of them has many iterations but still smaller than the above
           limit, or if in a body of some loop or even outside of a loop too
           many expressions need to be evaluated, the resulting constexpr
           evaluation might take too long.  The default is 33554432 (1<<25).

       -fcoroutines
           Enable support for the C++ coroutines extension (experimental).

       -fno-elide-constructors
           The C++ standard allows an implementation to omit creating a
           temporary that is only used to initialize another object of the same
           type.  Specifying this option disables that optimization, and forces
           G++ to call the copy constructor in all cases.  This option also
           causes G++ to call trivial member functions which otherwise would be
           expanded inline.

           In C++17, the compiler is required to omit these temporaries, but
           this option still affects trivial member functions.

       -fno-enforce-eh-specs
           Don't generate code to check for violation of exception
           specifications at run time.  This option violates the C++ standard,
           but may be useful for reducing code size in production builds, much
           like defining "NDEBUG".  This does not give user code permission to
           throw exceptions in violation of the exception specifications; the
           compiler still optimizes based on the specifications, so throwing an
           unexpected exception results in undefined behavior at run time.

       -fextern-tls-init
       -fno-extern-tls-init
           The C++11 and OpenMP standards allow "thread_local" and
           "threadprivate" variables to have dynamic (runtime) initialization.
           To support this, any use of such a variable goes through a wrapper
           function that performs any necessary initialization.  When the use
           and definition of the variable are in the same translation unit, this
           overhead can be optimized away, but when the use is in a different
           translation unit there is significant overhead even if the variable
           doesn't actually need dynamic initialization.  If the programmer can
           be sure that no use of the variable in a non-defining TU needs to
           trigger dynamic initialization (either because the variable is
           statically initialized, or a use of the variable in the defining TU
           will be executed before any uses in another TU), they can avoid this
           overhead with the -fno-extern-tls-init option.

           On targets that support symbol aliases, the default is
           -fextern-tls-init.  On targets that do not support symbol aliases,
           the default is -fno-extern-tls-init.

       -fno-gnu-keywords
           Do not recognize "typeof" as a keyword, so that code can use this
           word as an identifier.  You can use the keyword "__typeof__" instead.
           This option is implied by the strict ISO C++ dialects: -ansi,
           -std=c++98, -std=c++11, etc.

       -fno-implicit-templates
           Never emit code for non-inline templates that are instantiated
           implicitly (i.e. by use); only emit code for explicit instantiations.
           If you use this option, you must take care to structure your code to
           include all the necessary explicit instantiations to avoid getting
           undefined symbols at link time.

       -fno-implicit-inline-templates
           Don't emit code for implicit instantiations of inline templates,
           either.  The default is to handle inlines differently so that
           compiles with and without optimization need the same set of explicit
           instantiations.

       -fno-implement-inlines
           To save space, do not emit out-of-line copies of inline functions
           controlled by "#pragma implementation".  This causes linker errors if
           these functions are not inlined everywhere they are called.

       -fmodules-ts
       -fno-modules-ts
           Enable support for C++20 modules   The -fno-modules-ts is usually not
           needed, as that is the default.  Even though this is a C++20 feature,
           it is not currently implicitly enabled by selecting that standard
           version.

       -fmodule-header
       -fmodule-header=user
       -fmodule-header=system
           Compile a header file to create an importable header unit.

       -fmodule-implicit-inline
           Member functions defined in their class definitions are not
           implicitly inline for modular code.  This is different to traditional
           C++ behavior, for good reasons.  However, it may result in a
           difficulty during code porting.  This option makes such function
           definitions implicitly inline.  It does however generate an ABI
           incompatibility, so you must use it everywhere or nowhere.  (Such
           definitions outside of a named module remain implicitly inline,
           regardless.)

       -fno-module-lazy
           Disable lazy module importing and module mapper creation.

       -fmodule-mapper=[hostname]:port[?ident]
       -fmodule-mapper=|program[?ident] args...
       -fmodule-mapper==socket[?ident]
       -fmodule-mapper=<>[inout][?ident]
       -fmodule-mapper=<in>out[?ident]
       -fmodule-mapper=file[?ident]
           An oracle to query for module name to filename mappings.  If
           unspecified the CXX_MODULE_MAPPER environment variable is used, and
           if that is unset, an in-process default is provided.

       -fmodule-only
           Only emit the Compiled Module Interface, inhibiting any object file.

       -fms-extensions
           Disable Wpedantic warnings about constructs used in MFC, such as
           implicit int and getting a pointer to member function via non-
           standard syntax.

       -fnew-inheriting-ctors
           Enable the P0136 adjustment to the semantics of C++11 constructor
           inheritance.  This is part of C++17 but also considered to be a
           Defect Report against C++11 and C++14.  This flag is enabled by
           default unless -fabi-version=10 or lower is specified.

       -fnew-ttp-matching
           Enable the P0522 resolution to Core issue 150, template template
           parameters and default arguments: this allows a template with default
           template arguments as an argument for a template template parameter
           with fewer template parameters.  This flag is enabled by default for
           -std=c++17.

       -fno-nonansi-builtins
           Disable built-in declarations of functions that are not mandated by
           ANSI/ISO C.  These include "ffs", "alloca", "_exit", "index",
           "bzero", "conjf", and other related functions.

       -fnothrow-opt
           Treat a "throw()" exception specification as if it were a "noexcept"
           specification to reduce or eliminate the text size overhead relative
           to a function with no exception specification.  If the function has
           local variables of types with non-trivial destructors, the exception
           specification actually makes the function smaller because the EH
           cleanups for those variables can be optimized away.  The semantic
           effect is that an exception thrown out of a function with such an
           exception specification results in a call to "terminate" rather than
           "unexpected".

       -fno-operator-names
           Do not treat the operator name keywords "and", "bitand", "bitor",
           "compl", "not", "or" and "xor" as synonyms as keywords.

       -fno-optional-diags
           Disable diagnostics that the standard says a compiler does not need
           to issue.  Currently, the only such diagnostic issued by G++ is the
           one for a name having multiple meanings within a class.

       -fpermissive
           Downgrade some diagnostics about nonconformant code from errors to
           warnings.  Thus, using -fpermissive allows some nonconforming code to
           compile.

       -fno-pretty-templates
           When an error message refers to a specialization of a function
           template, the compiler normally prints the signature of the template
           followed by the template arguments and any typedefs or typenames in
           the signature (e.g. "void f(T) [with T = int]" rather than "void
           f(int)") so that it's clear which template is involved.  When an
           error message refers to a specialization of a class template, the
           compiler omits any template arguments that match the default template
           arguments for that template.  If either of these behaviors make it
           harder to understand the error message rather than easier, you can
           use -fno-pretty-templates to disable them.

       -fno-rtti
           Disable generation of information about every class with virtual
           functions for use by the C++ run-time type identification features
           ("dynamic_cast" and "typeid").  If you don't use those parts of the
           language, you can save some space by using this flag.  Note that
           exception handling uses the same information, but G++ generates it as
           needed. The "dynamic_cast" operator can still be used for casts that
           do not require run-time type information, i.e. casts to "void *" or
           to unambiguous base classes.

           Mixing code compiled with -frtti with that compiled with -fno-rtti
           may not work.  For example, programs may fail to link if a class
           compiled with -fno-rtti is used as a base for a class compiled with
           -frtti.

       -fsized-deallocation
           Enable the built-in global declarations

                   void operator delete (void *, std::size_t) noexcept;
                   void operator delete[] (void *, std::size_t) noexcept;

           as introduced in C++14.  This is useful for user-defined replacement
           deallocation functions that, for example, use the size of the object
           to make deallocation faster.  Enabled by default under -std=c++14 and
           above.  The flag -Wsized-deallocation warns about places that might
           want to add a definition.

       -fstrict-enums
           Allow the compiler to optimize using the assumption that a value of
           enumerated type can only be one of the values of the enumeration (as
           defined in the C++ standard; basically, a value that can be
           represented in the minimum number of bits needed to represent all the
           enumerators).  This assumption may not be valid if the program uses a
           cast to convert an arbitrary integer value to the enumerated type.

       -fstrong-eval-order
           Evaluate member access, array subscripting, and shift expressions in
           left-to-right order, and evaluate assignment in right-to-left order,
           as adopted for C++17.  Enabled by default with -std=c++17.
           -fstrong-eval-order=some enables just the ordering of member access
           and shift expressions, and is the default without -std=c++17.

       -ftemplate-backtrace-limit=n
           Set the maximum number of template instantiation notes for a single
           warning or error to n.  The default value is 10.

       -ftemplate-depth=n
           Set the maximum instantiation depth for template classes to n.  A
           limit on the template instantiation depth is needed to detect endless
           recursions during template class instantiation.  ANSI/ISO C++
           conforming programs must not rely on a maximum depth greater than 17
           (changed to 1024 in C++11).  The default value is 900, as the
           compiler can run out of stack space before hitting 1024 in some
           situations.

       -fno-threadsafe-statics
           Do not emit the extra code to use the routines specified in the C++
           ABI for thread-safe initialization of local statics.  You can use
           this option to reduce code size slightly in code that doesn't need to
           be thread-safe.

       -fuse-cxa-atexit
           Register destructors for objects with static storage duration with
           the "__cxa_atexit" function rather than the "atexit" function.  This
           option is required for fully standards-compliant handling of static
           destructors, but only works if your C library supports
           "__cxa_atexit".

       -fno-use-cxa-get-exception-ptr
           Don't use the "__cxa_get_exception_ptr" runtime routine.  This causes
           "std::uncaught_exception" to be incorrect, but is necessary if the
           runtime routine is not available.

       -fvisibility-inlines-hidden
           This switch declares that the user does not attempt to compare
           pointers to inline functions or methods where the addresses of the
           two functions are taken in different shared objects.

           The effect of this is that GCC may, effectively, mark inline methods
           with "__attribute__ ((visibility ("hidden")))" so that they do not
           appear in the export table of a DSO and do not require a PLT
           indirection when used within the DSO.  Enabling this option can have
           a dramatic effect on load and link times of a DSO as it massively
           reduces the size of the dynamic export table when the library makes
           heavy use of templates.

           The behavior of this switch is not quite the same as marking the
           methods as hidden directly, because it does not affect static
           variables local to the function or cause the compiler to deduce that
           the function is defined in only one shared object.

           You may mark a method as having a visibility explicitly to negate the
           effect of the switch for that method.  For example, if you do want to
           compare pointers to a particular inline method, you might mark it as
           having default visibility.  Marking the enclosing class with explicit
           visibility has no effect.

           Explicitly instantiated inline methods are unaffected by this option
           as their linkage might otherwise cross a shared library boundary.

       -fvisibility-ms-compat
           This flag attempts to use visibility settings to make GCC's C++
           linkage model compatible with that of Microsoft Visual Studio.

           The flag makes these changes to GCC's linkage model:

           1.  It sets the default visibility to "hidden", like
               -fvisibility=hidden.

           2.  Types, but not their members, are not hidden by default.

           3.  The One Definition Rule is relaxed for types without explicit
               visibility specifications that are defined in more than one
               shared object: those declarations are permitted if they are
               permitted when this option is not used.

           In new code it is better to use -fvisibility=hidden and export those
           classes that are intended to be externally visible.  Unfortunately it
           is possible for code to rely, perhaps accidentally, on the Visual
           Studio behavior.

           Among the consequences of these changes are that static data members
           of the same type with the same name but defined in different shared
           objects are different, so changing one does not change the other; and
           that pointers to function members defined in different shared objects
           may not compare equal.  When this flag is given, it is a violation of
           the ODR to define types with the same name differently.

       -fno-weak
           Do not use weak symbol support, even if it is provided by the linker.
           By default, G++ uses weak symbols if they are available.  This option
           exists only for testing, and should not be used by end-users; it
           results in inferior code and has no benefits.  This option may be
           removed in a future release of G++.

       -fext-numeric-literals (C++ and Objective-C++ only)
           Accept imaginary, fixed-point, or machine-defined literal number
           suffixes as GNU extensions.  When this option is turned off these
           suffixes are treated as C++11 user-defined literal numeric suffixes.
           This is on by default for all pre-C++11 dialects and all GNU
           dialects: -std=c++98, -std=gnu++98, -std=gnu++11, -std=gnu++14.  This
           option is off by default for ISO C++11 onwards (-std=c++11, ...).

       -nostdinc++
           Do not search for header files in the standard directories specific
           to C++, but do still search the other standard directories.  (This
           option is used when building the C++ library.)

       -flang-info-include-translate
       -flang-info-include-translate-not
       -flang-info-include-translate=header
           Inform of include translation events.  The first will note accepted
           include translations, the second will note declined include
           translations.  The header form will inform of include translations
           relating to that specific header.  If header is of the form "user" or
           "<system>" it will be resolved to a specific user or system header
           using the include path.

       -flang-info-module-cmi
       -flang-info-module-cmi=module
           Inform of Compiled Module Interface pathnames.  The first will note
           all read CMI pathnames.  The module form will not reading a specific
           module's CMI.  module may be a named module or a header-unit (the
           latter indicated by either being a pathname containing directory
           separators or enclosed in "<>" or "").

       -stdlib=libstdc++,libc++
           When G++ is configured to support this option, it allows
           specification of alternate C++ runtime libraries.  Two options are
           available: libstdc++ (the default, native C++ runtime for G++) and
           libc++ which is the C++ runtime installed on some operating systems
           (e.g. Darwin versions from Darwin11 onwards).  The option switches
           G++ to use the headers from the specified library and to emit
           "-lstdc++" or "-lc++" respectively, when a C++ runtime is required
           for linking.

       In addition, these warning options have meanings only for C++ programs:

       -Wabi-tag (C++ and Objective-C++ only)
           Warn when a type with an ABI tag is used in a context that does not
           have that ABI tag.  See C++ Attributes for more information about ABI
           tags.

       -Wcomma-subscript (C++ and Objective-C++ only)
           Warn about uses of a comma expression within a subscripting
           expression.  This usage was deprecated in C++20.  However, a comma
           expression wrapped in "( )" is not deprecated.  Example:

                   void f(int *a, int b, int c) {
                       a[b,c];     // deprecated
                       a[(b,c)];   // OK
                   }

           Enabled by default with -std=c++20.

       -Wctad-maybe-unsupported (C++ and Objective-C++ only)
           Warn when performing class template argument deduction (CTAD) on a
           type with no explicitly written deduction guides.  This warning will
           point out cases where CTAD succeeded only because the compiler
           synthesized the implicit deduction guides, which might not be what
           the programmer intended.  Certain style guides allow CTAD only on
           types that specifically "opt-in"; i.e., on types that are designed to
           support CTAD.  This warning can be suppressed with the following
           pattern:

                   struct allow_ctad_t; // any name works
                   template <typename T> struct S {
                     S(T) { }
                   };
                   S(allow_ctad_t) -> S<void>; // guide with incomplete parameter type will never be considered

       -Wctor-dtor-privacy (C++ and Objective-C++ only)
           Warn when a class seems unusable because all the constructors or
           destructors in that class are private, and it has neither friends nor
           public static member functions.  Also warn if there are no non-
           private methods, and there's at least one private member function
           that isn't a constructor or destructor.

       -Wdelete-non-virtual-dtor (C++ and Objective-C++ only)
           Warn when "delete" is used to destroy an instance of a class that has
           virtual functions and non-virtual destructor. It is unsafe to delete
           an instance of a derived class through a pointer to a base class if
           the base class does not have a virtual destructor.  This warning is
           enabled by -Wall.

       -Wdeprecated-copy (C++ and Objective-C++ only)
           Warn that the implicit declaration of a copy constructor or copy
           assignment operator is deprecated if the class has a user-provided
           copy constructor or copy assignment operator, in C++11 and up.  This
           warning is enabled by -Wextra.  With -Wdeprecated-copy-dtor, also
           deprecate if the class has a user-provided destructor.

       -Wno-deprecated-enum-enum-conversion (C++ and Objective-C++ only)
           Disable the warning about the case when the usual arithmetic
           conversions are applied on operands where one is of enumeration type
           and the other is of a different enumeration type.  This conversion
           was deprecated in C++20.  For example:

                   enum E1 { e };
                   enum E2 { f };
                   int k = f - e;

           -Wdeprecated-enum-enum-conversion is enabled by default with
           -std=c++20.  In pre-C++20 dialects, this warning can be enabled by
           -Wenum-conversion.

       -Wno-deprecated-enum-float-conversion (C++ and Objective-C++ only)
           Disable the warning about the case when the usual arithmetic
           conversions are applied on operands where one is of enumeration type
           and the other is of a floating-point type.  This conversion was
           deprecated in C++20.  For example:

                   enum E1 { e };
                   enum E2 { f };
                   bool b = e <= 3.7;

           -Wdeprecated-enum-float-conversion is enabled by default with
           -std=c++20.  In pre-C++20 dialects, this warning can be enabled by
           -Wenum-conversion.

       -Wno-init-list-lifetime (C++ and Objective-C++ only)
           Do not warn about uses of "std::initializer_list" that are likely to
           result in dangling pointers.  Since the underlying array for an
           "initializer_list" is handled like a normal C++ temporary object, it
           is easy to inadvertently keep a pointer to the array past the end of
           the array's lifetime.  For example:

           *   If a function returns a temporary "initializer_list", or a local
               "initializer_list" variable, the array's lifetime ends at the end
               of the return statement, so the value returned has a dangling
               pointer.

           *   If a new-expression creates an "initializer_list", the array only
               lives until the end of the enclosing full-expression, so the
               "initializer_list" in the heap has a dangling pointer.

           *   When an "initializer_list" variable is assigned from a brace-
               enclosed initializer list, the temporary array created for the
               right side of the assignment only lives until the end of the
               full-expression, so at the next statement the "initializer_list"
               variable has a dangling pointer.

                       // li's initial underlying array lives as long as li
                       std::initializer_list<int> li = { 1,2,3 };
                       // assignment changes li to point to a temporary array
                       li = { 4, 5 };
                       // now the temporary is gone and li has a dangling pointer
                       int i = li.begin()[0] // undefined behavior

           *   When a list constructor stores the "begin" pointer from the
               "initializer_list" argument, this doesn't extend the lifetime of
               the array, so if a class variable is constructed from a temporary
               "initializer_list", the pointer is left dangling by the end of
               the variable declaration statement.

       -Winvalid-imported-macros
           Verify all imported macro definitions are valid at the end of
           compilation.  This is not enabled by default, as it requires
           additional processing to determine.  It may be useful when preparing
           sets of header-units to ensure consistent macros.

       -Wno-literal-suffix (C++ and Objective-C++ only)
           Do not warn when a string or character literal is followed by a ud-
           suffix which does not begin with an underscore.  As a conforming
           extension, GCC treats such suffixes as separate preprocessing tokens
           in order to maintain backwards compatibility with code that uses
           formatting macros from "<inttypes.h>".  For example:

                   #define __STDC_FORMAT_MACROS
                   #include <inttypes.h>
                   #include <stdio.h>

                   int main() {
                     int64_t i64 = 123;
                     printf("My int64: %" PRId64"\n", i64);
                   }

           In this case, "PRId64" is treated as a separate preprocessing token.

           This option also controls warnings when a user-defined literal
           operator is declared with a literal suffix identifier that doesn't
           begin with an underscore. Literal suffix identifiers that don't begin
           with an underscore are reserved for future standardization.

           These warnings are enabled by default.

       -Wno-narrowing (C++ and Objective-C++ only)
           For C++11 and later standards, narrowing conversions are diagnosed by
           default, as required by the standard.  A narrowing conversion from a
           constant produces an error, and a narrowing conversion from a non-
           constant produces a warning, but -Wno-narrowing suppresses the
           diagnostic.  Note that this does not affect the meaning of well-
           formed code; narrowing conversions are still considered ill-formed in
           SFINAE contexts.

           With -Wnarrowing in C++98, warn when a narrowing conversion
           prohibited by C++11 occurs within { }, e.g.

                   int i = { 2.2 }; // error: narrowing from double to int

           This flag is included in -Wall and -Wc++11-compat.

       -Wnoexcept (C++ and Objective-C++ only)
           Warn when a noexcept-expression evaluates to false because of a call
           to a function that does not have a non-throwing exception
           specification (i.e. "throw()" or "noexcept") but is known by the
           compiler to never throw an exception.

       -Wnoexcept-type (C++ and Objective-C++ only)
           Warn if the C++17 feature making "noexcept" part of a function type
           changes the mangled name of a symbol relative to C++14.  Enabled by
           -Wabi and -Wc++17-compat.

           As an example:

                   template <class T> void f(T t) { t(); };
                   void g() noexcept;
                   void h() { f(g); }

           In C++14, "f" calls "f<void(*)()>", but in C++17 it calls
           "f<void(*)()noexcept>".

       -Wclass-memaccess (C++ and Objective-C++ only)
           Warn when the destination of a call to a raw memory function such as
           "memset" or "memcpy" is an object of class type, and when writing
           into such an object might bypass the class non-trivial or deleted
           constructor or copy assignment, violate const-correctness or
           encapsulation, or corrupt virtual table pointers.  Modifying the
           representation of such objects may violate invariants maintained by
           member functions of the class.  For example, the call to "memset"
           below is undefined because it modifies a non-trivial class object and
           is, therefore, diagnosed.  The safe way to either initialize or clear
           the storage of objects of such types is by using the appropriate
           constructor or assignment operator, if one is available.

                   std::string str = "abc";
                   memset (&str, 0, sizeof str);

           The -Wclass-memaccess option is enabled by -Wall.  Explicitly casting
           the pointer to the class object to "void *" or to a type that can be
           safely accessed by the raw memory function suppresses the warning.

       -Wnon-virtual-dtor (C++ and Objective-C++ only)
           Warn when a class has virtual functions and an accessible non-virtual
           destructor itself or in an accessible polymorphic base class, in
           which case it is possible but unsafe to delete an instance of a
           derived class through a pointer to the class itself or base class.
           This warning is automatically enabled if -Weffc++ is specified.

       -Wregister (C++ and Objective-C++ only)
           Warn on uses of the "register" storage class specifier, except when
           it is part of the GNU Explicit Register Variables extension.  The use
           of the "register" keyword as storage class specifier has been
           deprecated in C++11 and removed in C++17.  Enabled by default with
           -std=c++17.

       -Wreorder (C++ and Objective-C++ only)
           Warn when the order of member initializers given in the code does not
           match the order in which they must be executed.  For instance:

                   struct A {
                     int i;
                     int j;
                     A(): j (0), i (1) { }
                   };

           The compiler rearranges the member initializers for "i" and "j" to
           match the declaration order of the members, emitting a warning to
           that effect.  This warning is enabled by -Wall.

       -Wno-pessimizing-move (C++ and Objective-C++ only)
           This warning warns when a call to "std::move" prevents copy elision.
           A typical scenario when copy elision can occur is when returning in a
           function with a class return type, when the expression being returned
           is the name of a non-volatile automatic object, and is not a function
           parameter, and has the same type as the function return type.

                   struct T {
                   ...
                   };
                   T fn()
                   {
                     T t;
                     ...
                     return std::move (t);
                   }

           But in this example, the "std::move" call prevents copy elision.

           This warning is enabled by -Wall.

       -Wno-redundant-move (C++ and Objective-C++ only)
           This warning warns about redundant calls to "std::move"; that is,
           when a move operation would have been performed even without the
           "std::move" call.  This happens because the compiler is forced to
           treat the object as if it were an rvalue in certain situations such
           as returning a local variable, where copy elision isn't applicable.
           Consider:

                   struct T {
                   ...
                   };
                   T fn(T t)
                   {
                     ...
                     return std::move (t);
                   }

           Here, the "std::move" call is redundant.  Because G++ implements Core
           Issue 1579, another example is:

                   struct T { // convertible to U
                   ...
                   };
                   struct U {
                   ...
                   };
                   U fn()
                   {
                     T t;
                     ...
                     return std::move (t);
                   }

           In this example, copy elision isn't applicable because the type of
           the expression being returned and the function return type differ,
           yet G++ treats the return value as if it were designated by an
           rvalue.

           This warning is enabled by -Wextra.

       -Wrange-loop-construct (C++ and Objective-C++ only)
           This warning warns when a C++ range-based for-loop is creating an
           unnecessary copy.  This can happen when the range declaration is not
           a reference, but probably should be.  For example:

                   struct S { char arr[128]; };
                   void fn () {
                     S arr[5];
                     for (const auto x : arr) { ... }
                   }

           It does not warn when the type being copied is a trivially-copyable
           type whose size is less than 64 bytes.

           This warning also warns when a loop variable in a range-based for-
           loop is initialized with a value of a different type resulting in a
           copy.  For example:

                   void fn() {
                     int arr[10];
                     for (const double &x : arr) { ... }
                   }

           In the example above, in every iteration of the loop a temporary
           value of type "double" is created and destroyed, to which the
           reference "const double &" is bound.

           This warning is enabled by -Wall.

       -Wredundant-tags (C++ and Objective-C++ only)
           Warn about redundant class-key and enum-key in references to class
           types and enumerated types in contexts where the key can be
           eliminated without causing an ambiguity.  For example:

                   struct foo;
                   struct foo *p;   // warn that keyword struct can be eliminated

           On the other hand, in this example there is no warning:

                   struct foo;
                   void foo ();   // "hides" struct foo
                   void bar (struct foo&);  // no warning, keyword struct is necessary

       -Wno-subobject-linkage (C++ and Objective-C++ only)
           Do not warn if a class type has a base or a field whose type uses the
           anonymous namespace or depends on a type with no linkage.  If a type
           A depends on a type B with no or internal linkage, defining it in
           multiple translation units would be an ODR violation because the
           meaning of B is different in each translation unit.  If A only
           appears in a single translation unit, the best way to silence the
           warning is to give it internal linkage by putting it in an anonymous
           namespace as well.  The compiler doesn't give this warning for types
           defined in the main .C file, as those are unlikely to have multiple
           definitions.  -Wsubobject-linkage is enabled by default.

       -Weffc++ (C++ and Objective-C++ only)
           Warn about violations of the following style guidelines from Scott
           Meyers' Effective C++ series of books:

           *   Define a copy constructor and an assignment operator for classes
               with dynamically-allocated memory.

           *   Prefer initialization to assignment in constructors.

           *   Have "operator=" return a reference to *this.

           *   Don't try to return a reference when you must return an object.

           *   Distinguish between prefix and postfix forms of increment and
               decrement operators.

           *   Never overload "&&", "||", or ",".

           This option also enables -Wnon-virtual-dtor, which is also one of the
           effective C++ recommendations.  However, the check is extended to
           warn about the lack of virtual destructor in accessible non-
           polymorphic bases classes too.

           When selecting this option, be aware that the standard library
           headers do not obey all of these guidelines; use grep -v to filter
           out those warnings.

       -Wno-exceptions (C++ and Objective-C++ only)
           Disable the warning about the case when an exception handler is
           shadowed by another handler, which can point out a wrong ordering of
           exception handlers.

       -Wstrict-null-sentinel (C++ and Objective-C++ only)
           Warn about the use of an uncasted "NULL" as sentinel.  When compiling
           only with GCC this is a valid sentinel, as "NULL" is defined to
           "__null".  Although it is a null pointer constant rather than a null
           pointer, it is guaranteed to be of the same size as a pointer.  But
           this use is not portable across different compilers.

       -Wno-non-template-friend (C++ and Objective-C++ only)
           Disable warnings when non-template friend functions are declared
           within a template.  In very old versions of GCC that predate
           implementation of the ISO standard, declarations such as friend int
           foo(int), where the name of the friend is an unqualified-id, could be
           interpreted as a particular specialization of a template function;
           the warning exists to diagnose compatibility problems, and is enabled
           by default.

       -Wold-style-cast (C++ and Objective-C++ only)
           Warn if an old-style (C-style) cast to a non-void type is used within
           a C++ program.  The new-style casts ("dynamic_cast", "static_cast",
           "reinterpret_cast", and "const_cast") are less vulnerable to
           unintended effects and much easier to search for.

       -Woverloaded-virtual (C++ and Objective-C++ only)
           Warn when a function declaration hides virtual functions from a base
           class.  For example, in:

                   struct A {
                     virtual void f();
                   };

                   struct B: public A {
                     void f(int);
                   };

           the "A" class version of "f" is hidden in "B", and code like:

                   B* b;
                   b->f();

           fails to compile.

       -Wno-pmf-conversions (C++ and Objective-C++ only)
           Disable the diagnostic for converting a bound pointer to member
           function to a plain pointer.

       -Wsign-promo (C++ and Objective-C++ only)
           Warn when overload resolution chooses a promotion from unsigned or
           enumerated type to a signed type, over a conversion to an unsigned
           type of the same size.  Previous versions of G++ tried to preserve
           unsignedness, but the standard mandates the current behavior.

       -Wtemplates (C++ and Objective-C++ only)
           Warn when a primary template declaration is encountered.  Some coding
           rules disallow templates, and this may be used to enforce that rule.
           The warning is inactive inside a system header file, such as the STL,
           so one can still use the STL.  One may also instantiate or specialize
           templates.

       -Wno-mismatched-new-delete (C++ and Objective-C++ only)
           Warn for mismatches between calls to "operator new" or "operator
           delete" and the corresponding call to the allocation or deallocation
           function.  This includes invocations of C++ "operator delete" with
           pointers returned from either mismatched forms of "operator new", or
           from other functions that allocate objects for which the "operator
           delete" isn't a suitable deallocator, as well as calls to other
           deallocation functions with pointers returned from "operator new" for
           which the deallocation function isn't suitable.

           For example, the "delete" expression in the function below is
           diagnosed because it doesn't match the array form of the "new"
           expression the pointer argument was returned from.  Similarly, the
           call to "free" is also diagnosed.

                   void f ()
                   {
                     int *a = new int[n];
                     delete a;   // warning: mismatch in array forms of expressions

                     char *p = new char[n];
                     free (p);   // warning: mismatch between new and free
                   }

           The related option -Wmismatched-dealloc diagnoses mismatches
           involving allocation and deallocation functions other than "operator
           new" and "operator delete".

           -Wmismatched-new-delete is enabled by default.

       -Wmismatched-tags (C++ and Objective-C++ only)
           Warn for declarations of structs, classes, and class templates and
           their specializations with a class-key that does not match either the
           definition or the first declaration if no definition is provided.

           For example, the declaration of "struct Object" in the argument list
           of "draw" triggers the warning.  To avoid it, either remove the
           redundant class-key "struct" or replace it with "class" to match its
           definition.

                   class Object {
                   public:
                     virtual ~Object () = 0;
                   };
                   void draw (struct Object*);

           It is not wrong to declare a class with the class-key "struct" as the
           example above shows.  The -Wmismatched-tags option is intended to
           help achieve a consistent style of class declarations.  In code that
           is intended to be portable to Windows-based compilers the warning
           helps prevent unresolved references due to the difference in the
           mangling of symbols declared with different class-keys.  The option
           can be used either on its own or in conjunction with
           -Wredundant-tags.

       -Wmultiple-inheritance (C++ and Objective-C++ only)
           Warn when a class is defined with multiple direct base classes.  Some
           coding rules disallow multiple inheritance, and this may be used to
           enforce that rule.  The warning is inactive inside a system header
           file, such as the STL, so one can still use the STL.  One may also
           define classes that indirectly use multiple inheritance.

       -Wvirtual-inheritance
           Warn when a class is defined with a virtual direct base class.  Some
           coding rules disallow multiple inheritance, and this may be used to
           enforce that rule.  The warning is inactive inside a system header
           file, such as the STL, so one can still use the STL.  One may also
           define classes that indirectly use virtual inheritance.

       -Wno-virtual-move-assign
           Suppress warnings about inheriting from a virtual base with a non-
           trivial C++11 move assignment operator.  This is dangerous because if
           the virtual base is reachable along more than one path, it is moved
           multiple times, which can mean both objects end up in the moved-from
           state.  If the move assignment operator is written to avoid moving
           from a moved-from object, this warning can be disabled.

       -Wnamespaces
           Warn when a namespace definition is opened.  Some coding rules
           disallow namespaces, and this may be used to enforce that rule.  The
           warning is inactive inside a system header file, such as the STL, so
           one can still use the STL.  One may also use using directives and
           qualified names.

       -Wno-terminate (C++ and Objective-C++ only)
           Disable the warning about a throw-expression that will immediately
           result in a call to "terminate".

       -Wno-vexing-parse (C++ and Objective-C++ only)
           Warn about the most vexing parse syntactic ambiguity.  This warns
           about the cases when a declaration looks like a variable definition,
           but the C++ language requires it to be interpreted as a function
           declaration.  For instance:

                   void f(double a) {
                     int i();        // extern int i (void);
                     int n(int(a));  // extern int n (int);
                   }

           Another example:

                   struct S { S(int); };
                   void f(double a) {
                     S x(int(a));   // extern struct S x (int);
                     S y(int());    // extern struct S y (int (*) (void));
                     S z();         // extern struct S z (void);
                   }

           The warning will suggest options how to deal with such an ambiguity;
           e.g., it can suggest removing the parentheses or using braces
           instead.

           This warning is enabled by default.

       -Wno-class-conversion (C++ and Objective-C++ only)
           Do not warn when a conversion function converts an object to the same
           type, to a base class of that type, or to void; such a conversion
           function will never be called.

       -Wvolatile (C++ and Objective-C++ only)
           Warn about deprecated uses of the "volatile" qualifier.  This
           includes postfix and prefix "++" and "--" expressions of
           "volatile"-qualified types, using simple assignments where the left
           operand is a "volatile"-qualified non-class type for their value,
           compound assignments where the left operand is a "volatile"-qualified
           non-class type, "volatile"-qualified function return type,
           "volatile"-qualified parameter type, and structured bindings of a
           "volatile"-qualified type.  This usage was deprecated in C++20.

           Enabled by default with -std=c++20.

       -Wzero-as-null-pointer-constant (C++ and Objective-C++ only)
           Warn when a literal 0 is used as null pointer constant.  This can be
           useful to facilitate the conversion to "nullptr" in C++11.

       -Waligned-new
           Warn about a new-expression of a type that requires greater alignment
           than the "alignof(std::max_align_t)" but uses an allocation function
           without an explicit alignment parameter. This option is enabled by
           -Wall.

           Normally this only warns about global allocation functions, but
           -Waligned-new=all also warns about class member allocation functions.

       -Wno-placement-new
       -Wplacement-new=n
           Warn about placement new expressions with undefined behavior, such as
           constructing an object in a buffer that is smaller than the type of
           the object.  For example, the placement new expression below is
           diagnosed because it attempts to construct an array of 64 integers in
           a buffer only 64 bytes large.

                   char buf [64];
                   new (buf) int[64];

           This warning is enabled by default.

           -Wplacement-new=1
               This is the default warning level of -Wplacement-new.  At this
               level the warning is not issued for some strictly undefined
               constructs that GCC allows as extensions for compatibility with
               legacy code.  For example, the following "new" expression is not
               diagnosed at this level even though it has undefined behavior
               according to the C++ standard because it writes past the end of
               the one-element array.

                       struct S { int n, a[1]; };
                       S *s = (S *)malloc (sizeof *s + 31 * sizeof s->a[0]);
                       new (s->a)int [32]();

           -Wplacement-new=2
               At this level, in addition to diagnosing all the same constructs
               as at level 1, a diagnostic is also issued for placement new
               expressions that construct an object in the last member of
               structure whose type is an array of a single element and whose
               size is less than the size of the object being constructed.
               While the previous example would be diagnosed, the following
               construct makes use of the flexible member array extension to
               avoid the warning at level 2.

                       struct S { int n, a[]; };
                       S *s = (S *)malloc (sizeof *s + 32 * sizeof s->a[0]);
                       new (s->a)int [32]();

       -Wcatch-value
       -Wcatch-value=n (C++ and Objective-C++ only)
           Warn about catch handlers that do not catch via reference.  With
           -Wcatch-value=1 (or -Wcatch-value for short) warn about polymorphic
           class types that are caught by value.  With -Wcatch-value=2 warn
           about all class types that are caught by value. With -Wcatch-value=3
           warn about all types that are not caught by reference. -Wcatch-value
           is enabled by -Wall.

       -Wconditionally-supported (C++ and Objective-C++ only)
           Warn for conditionally-supported (C++11 [intro.defs]) constructs.

       -Wno-delete-incomplete (C++ and Objective-C++ only)
           Do not warn when deleting a pointer to incomplete type, which may
           cause undefined behavior at runtime.  This warning is enabled by
           default.

       -Wextra-semi (C++, Objective-C++ only)
           Warn about redundant semicolons after in-class function definitions.

       -Wno-inaccessible-base (C++, Objective-C++ only)
           This option controls warnings when a base class is inaccessible in a
           class derived from it due to ambiguity.  The warning is enabled by
           default.  Note that the warning for ambiguous virtual bases is
           enabled by the -Wextra option.

                   struct A { int a; };

                   struct B : A { };

                   struct C : B, A { };

       -Wno-inherited-variadic-ctor
           Suppress warnings about use of C++11 inheriting constructors when the
           base class inherited from has a C variadic constructor; the warning
           is on by default because the ellipsis is not inherited.

       -Wno-invalid-offsetof (C++ and Objective-C++ only)
           Suppress warnings from applying the "offsetof" macro to a non-POD
           type.  According to the 2014 ISO C++ standard, applying "offsetof" to
           a non-standard-layout type is undefined.  In existing C++
           implementations, however, "offsetof" typically gives meaningful
           results.  This flag is for users who are aware that they are writing
           nonportable code and who have deliberately chosen to ignore the
           warning about it.

           The restrictions on "offsetof" may be relaxed in a future version of
           the C++ standard.

       -Wsized-deallocation (C++ and Objective-C++ only)
           Warn about a definition of an unsized deallocation function

                   void operator delete (void *) noexcept;
                   void operator delete[] (void *) noexcept;

           without a definition of the corresponding sized deallocation function

                   void operator delete (void *, std::size_t) noexcept;
                   void operator delete[] (void *, std::size_t) noexcept;

           or vice versa.  Enabled by -Wextra along with -fsized-deallocation.

       -Wsuggest-final-types
           Warn about types with virtual methods where code quality would be
           improved if the type were declared with the C++11 "final" specifier,
           or, if possible, declared in an anonymous namespace. This allows GCC
           to more aggressively devirtualize the polymorphic calls. This warning
           is more effective with link-time optimization, where the information
           about the class hierarchy graph is more complete.

       -Wsuggest-final-methods
           Warn about virtual methods where code quality would be improved if
           the method were declared with the C++11 "final" specifier, or, if
           possible, its type were declared in an anonymous namespace or with
           the "final" specifier.  This warning is more effective with link-time
           optimization, where the information about the class hierarchy graph
           is more complete. It is recommended to first consider suggestions of
           -Wsuggest-final-types and then rebuild with new annotations.

       -Wsuggest-override
           Warn about overriding virtual functions that are not marked with the
           "override" keyword.

       -Wuseless-cast (C++ and Objective-C++ only)
           Warn when an expression is casted to its own type.

       -Wno-conversion-null (C++ and Objective-C++ only)
           Do not warn for conversions between "NULL" and non-pointer types.
           -Wconversion-null is enabled by default.

   Options Controlling Objective-C and Objective-C++ Dialects
       (NOTE: This manual does not describe the Objective-C and Objective-C++
       languages themselves.

       This section describes the command-line options that are only meaningful
       for Objective-C and Objective-C++ programs.  You can also use most of the
       language-independent GNU compiler options.  For example, you might
       compile a file some_class.m like this:

               gcc -g -fgnu-runtime -O -c some_class.m

       In this example, -fgnu-runtime is an option meant only for Objective-C
       and Objective-C++ programs; you can use the other options with any
       language supported by GCC.

       Note that since Objective-C is an extension of the C language, Objective-
       C compilations may also use options specific to the C front-end (e.g.,
       -Wtraditional).  Similarly, Objective-C++ compilations may use
       C++-specific options (e.g., -Wabi).

       Here is a list of options that are only for compiling Objective-C and
       Objective-C++ programs:

       -fconstant-string-class=class-name
           Use class-name as the name of the class to instantiate for each
           literal string specified with the syntax "@"..."".  The default class
           name is "NXConstantString" if the GNU runtime is being used, and
           "NSConstantString" if the NeXT runtime is being used (see below).
           The -fconstant-cfstrings option, if also present, overrides the
           -fconstant-string-class setting and cause "@"..."" literals to be
           laid out as constant CoreFoundation strings.

       -fgnu-runtime
           Generate object code compatible with the standard GNU Objective-C
           runtime.  This is the default for most types of systems.

       -fnext-runtime
           Generate output compatible with the NeXT runtime.  This is the
           default for NeXT-based systems, including Darwin and Mac OS X.  The
           macro "__NEXT_RUNTIME__" is predefined if (and only if) this option
           is used.

       -fno-nil-receivers
           Assume that all Objective-C message dispatches ("[receiver
           message:arg]") in this translation unit ensure that the receiver is
           not "nil".  This allows for more efficient entry points in the
           runtime to be used.  This option is only available in conjunction
           with the NeXT runtime and ABI version 0 or 1.

       -fobjc-abi-version=n
           Use version n of the Objective-C ABI for the selected runtime.  This
           option is currently supported only for the NeXT runtime.  In that
           case, Version 0 is the traditional (32-bit) ABI without support for
           properties and other Objective-C 2.0 additions.  Version 1 is the
           traditional (32-bit) ABI with support for properties and other
           Objective-C 2.0 additions.  Version 2 is the modern (64-bit) ABI.  If
           nothing is specified, the default is Version 0 on 32-bit target
           machines, and Version 2 on 64-bit target machines.

       -fobjc-call-cxx-cdtors
           For each Objective-C class, check if any of its instance variables is
           a C++ object with a non-trivial default constructor.  If so,
           synthesize a special "- (id) .cxx_construct" instance method which
           runs non-trivial default constructors on any such instance variables,
           in order, and then return "self".  Similarly, check if any instance
           variable is a C++ object with a non-trivial destructor, and if so,
           synthesize a special "- (void) .cxx_destruct" method which runs all
           such default destructors, in reverse order.

           The "- (id) .cxx_construct" and "- (void) .cxx_destruct" methods
           thusly generated only operate on instance variables declared in the
           current Objective-C class, and not those inherited from superclasses.
           It is the responsibility of the Objective-C runtime to invoke all
           such methods in an object's inheritance hierarchy.  The "- (id)
           .cxx_construct" methods are invoked by the runtime immediately after
           a new object instance is allocated; the "- (void) .cxx_destruct"
           methods are invoked immediately before the runtime deallocates an
           object instance.

           As of this writing, only the NeXT runtime on Mac OS X 10.4 and later
           has support for invoking the "- (id) .cxx_construct" and "- (void)
           .cxx_destruct" methods.

       -fobjc-direct-dispatch
           Allow fast jumps to the message dispatcher.  On Darwin this is
           accomplished via the comm page.

       -fobjc-exceptions
           Enable syntactic support for structured exception handling in
           Objective-C, similar to what is offered by C++.  This option is
           required to use the Objective-C keywords @try, @throw, @catch,
           @finally and @synchronized.  This option is available with both the
           GNU runtime and the NeXT runtime (but not available in conjunction
           with the NeXT runtime on Mac OS X 10.2 and earlier).

       -fobjc-gc
           Enable garbage collection (GC) in Objective-C and Objective-C++
           programs.  This option is only available with the NeXT runtime; the
           GNU runtime has a different garbage collection implementation that
           does not require special compiler flags.

       -fobjc-nilcheck
           For the NeXT runtime with version 2 of the ABI, check for a nil
           receiver in method invocations before doing the actual method call.
           This is the default and can be disabled using -fno-objc-nilcheck.
           Class methods and super calls are never checked for nil in this way
           no matter what this flag is set to.  Currently this flag does nothing
           when the GNU runtime, or an older version of the NeXT runtime ABI, is
           used.

       -fobjc-std=objc1
           Conform to the language syntax of Objective-C 1.0, the language
           recognized by GCC 4.0.  This only affects the Objective-C additions
           to the C/C++ language; it does not affect conformance to C/C++
           standards, which is controlled by the separate C/C++ dialect option
           flags.  When this option is used with the Objective-C or
           Objective-C++ compiler, any Objective-C syntax that is not recognized
           by GCC 4.0 is rejected.  This is useful if you need to make sure that
           your Objective-C code can be compiled with older versions of GCC.

       -freplace-objc-classes
           Emit a special marker instructing ld(1) not to statically link in the
           resulting object file, and allow dyld(1) to load it in at run time
           instead.  This is used in conjunction with the Fix-and-Continue
           debugging mode, where the object file in question may be recompiled
           and dynamically reloaded in the course of program execution, without
           the need to restart the program itself.  Currently, Fix-and-Continue
           functionality is only available in conjunction with the NeXT runtime
           on Mac OS X 10.3 and later.

       -fzero-link
           When compiling for the NeXT runtime, the compiler ordinarily replaces
           calls to "objc_getClass("...")" (when the name of the class is known
           at compile time) with static class references that get initialized at
           load time, which improves run-time performance.  Specifying the
           -fzero-link flag suppresses this behavior and causes calls to
           "objc_getClass("...")"  to be retained.  This is useful in Zero-Link
           debugging mode, since it allows for individual class implementations
           to be modified during program execution.  The GNU runtime currently
           always retains calls to "objc_get_class("...")"  regardless of
           command-line options.

       -fno-local-ivars
           By default instance variables in Objective-C can be accessed as if
           they were local variables from within the methods of the class
           they're declared in.  This can lead to shadowing between instance
           variables and other variables declared either locally inside a class
           method or globally with the same name.  Specifying the
           -fno-local-ivars flag disables this behavior thus avoiding variable
           shadowing issues.

       -fivar-visibility=[public|protected|private|package]
           Set the default instance variable visibility to the specified option
           so that instance variables declared outside the scope of any access
           modifier directives default to the specified visibility.

       -gen-decls
           Dump interface declarations for all classes seen in the source file
           to a file named sourcename.decl.

       -Wassign-intercept (Objective-C and Objective-C++ only)
           Warn whenever an Objective-C assignment is being intercepted by the
           garbage collector.

       -Wno-property-assign-default (Objective-C and Objective-C++ only)
           Do not warn if a property for an Objective-C object has no assign
           semantics specified.

       -Wno-protocol (Objective-C and Objective-C++ only)
           If a class is declared to implement a protocol, a warning is issued
           for every method in the protocol that is not implemented by the
           class.  The default behavior is to issue a warning for every method
           not explicitly implemented in the class, even if a method
           implementation is inherited from the superclass.  If you use the
           -Wno-protocol option, then methods inherited from the superclass are
           considered to be implemented, and no warning is issued for them.

       -Wobjc-root-class (Objective-C and Objective-C++ only)
           Warn if a class interface lacks a superclass. Most classes will
           inherit from "NSObject" (or "Object") for example.  When declaring
           classes intended to be root classes, the warning can be suppressed by
           marking their interfaces with "__attribute__((objc_root_class))".

       -Wselector (Objective-C and Objective-C++ only)
           Warn if multiple methods of different types for the same selector are
           found during compilation.  The check is performed on the list of
           methods in the final stage of compilation.  Additionally, a check is
           performed for each selector appearing in a "@selector(...)"
           expression, and a corresponding method for that selector has been
           found during compilation.  Because these checks scan the method table
           only at the end of compilation, these warnings are not produced if
           the final stage of compilation is not reached, for example because an
           error is found during compilation, or because the -fsyntax-only
           option is being used.

       -Wstrict-selector-match (Objective-C and Objective-C++ only)
           Warn if multiple methods with differing argument and/or return types
           are found for a given selector when attempting to send a message
           using this selector to a receiver of type "id" or "Class".  When this
           flag is off (which is the default behavior), the compiler omits such
           warnings if any differences found are confined to types that share
           the same size and alignment.

       -Wundeclared-selector (Objective-C and Objective-C++ only)
           Warn if a "@selector(...)" expression referring to an undeclared
           selector is found.  A selector is considered undeclared if no method
           with that name has been declared before the "@selector(...)"
           expression, either explicitly in an @interface or @protocol
           declaration, or implicitly in an @implementation section.  This
           option always performs its checks as soon as a "@selector(...)"
           expression is found, while -Wselector only performs its checks in the
           final stage of compilation.  This also enforces the coding style
           convention that methods and selectors must be declared before being
           used.

       -print-objc-runtime-info
           Generate C header describing the largest structure that is passed by
           value, if any.

   Options to Control Diagnostic Messages Formatting
       Traditionally, diagnostic messages have been formatted irrespective of
       the output device's aspect (e.g. its width, ...).  You can use the
       options described below to control the formatting algorithm for
       diagnostic messages, e.g. how many characters per line, how often source
       location information should be reported.  Note that some language front
       ends may not honor these options.

       -fmessage-length=n
           Try to format error messages so that they fit on lines of about n
           characters.  If n is zero, then no line-wrapping is done; each error
           message appears on a single line.  This is the default for all front
           ends.

           Note - this option also affects the display of the #error and
           #warning pre-processor directives, and the deprecated
           function/type/variable attribute.  It does not however affect the
           pragma GCC warning and pragma GCC error pragmas.

       -fdiagnostics-plain-output
           This option requests that diagnostic output look as plain as
           possible, which may be useful when running dejagnu or other utilities
           that need to parse diagnostics output and prefer that it remain more
           stable over time.  -fdiagnostics-plain-output is currently equivalent
           to the following options: -fno-diagnostics-show-caret
           -fno-diagnostics-show-line-numbers -fdiagnostics-color=never
           -fdiagnostics-urls=never -fdiagnostics-path-format=separate-events In
           the future, if GCC changes the default appearance of its diagnostics,
           the corresponding option to disable the new behavior will be added to
           this list.

       -fdiagnostics-show-location=once
           Only meaningful in line-wrapping mode.  Instructs the diagnostic
           messages reporter to emit source location information once; that is,
           in case the message is too long to fit on a single physical line and
           has to be wrapped, the source location won't be emitted (as prefix)
           again, over and over, in subsequent continuation lines.  This is the
           default behavior.

       -fdiagnostics-show-location=every-line
           Only meaningful in line-wrapping mode.  Instructs the diagnostic
           messages reporter to emit the same source location information (as
           prefix) for physical lines that result from the process of breaking a
           message which is too long to fit on a single line.

       -fdiagnostics-color[=WHEN]
       -fno-diagnostics-color
           Use color in diagnostics.  WHEN is never, always, or auto.  The
           default depends on how the compiler has been configured, it can be
           any of the above WHEN options or also never if GCC_COLORS environment
           variable isn't present in the environment, and auto otherwise.  auto
           makes GCC use color only when the standard error is a terminal, and
           when not executing in an emacs shell.  The forms -fdiagnostics-color
           and -fno-diagnostics-color are aliases for -fdiagnostics-color=always
           and -fdiagnostics-color=never, respectively.

           The colors are defined by the environment variable GCC_COLORS.  Its
           value is a colon-separated list of capabilities and Select Graphic
           Rendition (SGR) substrings. SGR commands are interpreted by the
           terminal or terminal emulator.  (See the section in the documentation
           of your text terminal for permitted values and their meanings as
           character attributes.)  These substring values are integers in
           decimal representation and can be concatenated with semicolons.
           Common values to concatenate include 1 for bold, 4 for underline, 5
           for blink, 7 for inverse, 39 for default foreground color, 30 to 37
           for foreground colors, 90 to 97 for 16-color mode foreground colors,
           38;5;0 to 38;5;255 for 88-color and 256-color modes foreground
           colors, 49 for default background color, 40 to 47 for background
           colors, 100 to 107 for 16-color mode background colors, and 48;5;0 to
           48;5;255 for 88-color and 256-color modes background colors.

           The default GCC_COLORS is

                   error=01;31:warning=01;35:note=01;36:range1=32:range2=34:locus=01:\
                   quote=01:path=01;36:fixit-insert=32:fixit-delete=31:\
                   diff-filename=01:diff-hunk=32:diff-delete=31:diff-insert=32:\
                   type-diff=01;32

           where 01;31 is bold red, 01;35 is bold magenta, 01;36 is bold cyan,
           32 is green, 34 is blue, 01 is bold, and 31 is red.  Setting
           GCC_COLORS to the empty string disables colors.  Supported
           capabilities are as follows.

           "error="
               SGR substring for error: markers.

           "warning="
               SGR substring for warning: markers.

           "note="
               SGR substring for note: markers.

           "path="
               SGR substring for colorizing paths of control-flow events as
               printed via -fdiagnostics-path-format=, such as the identifiers
               of individual events and lines indicating interprocedural calls
               and returns.

           "range1="
               SGR substring for first additional range.

           "range2="
               SGR substring for second additional range.

           "locus="
               SGR substring for location information, file:line or
               file:line:column etc.

           "quote="
               SGR substring for information printed within quotes.

           "fixit-insert="
               SGR substring for fix-it hints suggesting text to be inserted or
               replaced.

           "fixit-delete="
               SGR substring for fix-it hints suggesting text to be deleted.

           "diff-filename="
               SGR substring for filename headers within generated patches.

           "diff-hunk="
               SGR substring for the starts of hunks within generated patches.

           "diff-delete="
               SGR substring for deleted lines within generated patches.

           "diff-insert="
               SGR substring for inserted lines within generated patches.

           "type-diff="
               SGR substring for highlighting mismatching types within template
               arguments in the C++ frontend.

       -fdiagnostics-urls[=WHEN]
           Use escape sequences to embed URLs in diagnostics.  For example, when
           -fdiagnostics-show-option emits text showing the command-line option
           controlling a diagnostic, embed a URL for documentation of that
           option.

           WHEN is never, always, or auto.  auto makes GCC use URL escape
           sequences only when the standard error is a terminal, and when not
           executing in an emacs shell or any graphical terminal which is known
           to be incompatible with this feature, see below.

           The default depends on how the compiler has been configured.  It can
           be any of the above WHEN options.

           GCC can also be configured (via the
           --with-diagnostics-urls=auto-if-env configure-time option) so that
           the default is affected by environment variables.  Under such a
           configuration, GCC defaults to using auto if either GCC_URLS or
           TERM_URLS environment variables are present and non-empty in the
           environment of the compiler, or never if neither are.

           However, even with -fdiagnostics-urls=always the behavior is
           dependent on those environment variables: If GCC_URLS is set to empty
           or no, do not embed URLs in diagnostics.  If set to st, URLs use ST
           escape sequences.  If set to bel, the default, URLs use BEL escape
           sequences.  Any other non-empty value enables the feature.  If
           GCC_URLS is not set, use TERM_URLS as a fallback.  Note: ST is an
           ANSI escape sequence, string terminator ESC \, BEL is an ASCII
           character, CTRL-G that usually sounds like a beep.

           At this time GCC tries to detect also a few terminals that are known
           to not implement the URL feature, and have bugs or at least had bugs
           in some versions that are still in use, where the URL escapes are
           likely to misbehave, i.e. print garbage on the screen.  That list is
           currently xfce4-terminal, certain known to be buggy gnome-terminal
           versions, the linux console, and mingw.  This check can be skipped
           with the -fdiagnostics-urls=always.

       -fno-diagnostics-show-option
           By default, each diagnostic emitted includes text indicating the
           command-line option that directly controls the diagnostic (if such an
           option is known to the diagnostic machinery).  Specifying the
           -fno-diagnostics-show-option flag suppresses that behavior.

       -fno-diagnostics-show-caret
           By default, each diagnostic emitted includes the original source line
           and a caret ^ indicating the column.  This option suppresses this
           information.  The source line is truncated to n characters, if the
           -fmessage-length=n option is given.  When the output is done to the
           terminal, the width is limited to the width given by the COLUMNS
           environment variable or, if not set, to the terminal width.

       -fno-diagnostics-show-labels
           By default, when printing source code (via -fdiagnostics-show-caret),
           diagnostics can label ranges of source code with pertinent
           information, such as the types of expressions:

                       printf ("foo %s bar", long_i + long_j);
                                    ~^       ~~~~~~~~~~~~~~~
                                     |              |
                                     char *         long int

           This option suppresses the printing of these labels (in the example
           above, the vertical bars and the "char *" and "long int" text).

       -fno-diagnostics-show-cwe
           Diagnostic messages can optionally have an associated
           @url{https://cwe.mitre.org/index.html, CWE} identifier.  GCC itself
           only provides such metadata for some of the -fanalyzer diagnostics.
           GCC plugins may also provide diagnostics with such metadata.  By
           default, if this information is present, it will be printed with the
           diagnostic.  This option suppresses the printing of this metadata.

       -fno-diagnostics-show-line-numbers
           By default, when printing source code (via -fdiagnostics-show-caret),
           a left margin is printed, showing line numbers.  This option
           suppresses this left margin.

       -fdiagnostics-minimum-margin-width=width
           This option controls the minimum width of the left margin printed by
           -fdiagnostics-show-line-numbers.  It defaults to 6.

       -fdiagnostics-parseable-fixits
           Emit fix-it hints in a machine-parseable format, suitable for
           consumption by IDEs.  For each fix-it, a line will be printed after
           the relevant diagnostic, starting with the string "fix-it:".  For
           example:

                   fix-it:"test.c":{45:3-45:21}:"gtk_widget_show_all"

           The location is expressed as a half-open range, expressed as a count
           of bytes, starting at byte 1 for the initial column.  In the above
           example, bytes 3 through 20 of line 45 of "test.c" are to be replaced
           with the given string:

                   00000000011111111112222222222
                   12345678901234567890123456789
                     gtk_widget_showall (dlg);
                     ^^^^^^^^^^^^^^^^^^
                     gtk_widget_show_all

           The filename and replacement string escape backslash as "\\", tab as
           "\t", newline as "\n", double quotes as "\"", non-printable
           characters as octal (e.g. vertical tab as "\013").

           An empty replacement string indicates that the given range is to be
           removed.  An empty range (e.g. "45:3-45:3") indicates that the string
           is to be inserted at the given position.

       -fdiagnostics-generate-patch
           Print fix-it hints to stderr in unified diff format, after any
           diagnostics are printed.  For example:

                   --- test.c
                   +++ test.c
                   @ -42,5 +42,5 @

                    void show_cb(GtkDialog *dlg)
                    {
                   -  gtk_widget_showall(dlg);
                   +  gtk_widget_show_all(dlg);
                    }

           The diff may or may not be colorized, following the same rules as for
           diagnostics (see -fdiagnostics-color).

       -fdiagnostics-show-template-tree
           In the C++ frontend, when printing diagnostics showing mismatching
           template types, such as:

                     could not convert 'std::map<int, std::vector<double> >()'
                       from 'map<[...],vector<double>>' to 'map<[...],vector<float>>

           the -fdiagnostics-show-template-tree flag enables printing a tree-
           like structure showing the common and differing parts of the types,
           such as:

                     map<
                       [...],
                       vector<
                         [double != float]>>

           The parts that differ are highlighted with color ("double" and
           "float" in this case).

       -fno-elide-type
           By default when the C++ frontend prints diagnostics showing
           mismatching template types, common parts of the types are printed as
           "[...]" to simplify the error message.  For example:

                     could not convert 'std::map<int, std::vector<double> >()'
                       from 'map<[...],vector<double>>' to 'map<[...],vector<float>>

           Specifying the -fno-elide-type flag suppresses that behavior.  This
           flag also affects the output of the -fdiagnostics-show-template-tree
           flag.

       -fdiagnostics-path-format=KIND
           Specify how to print paths of control-flow events for diagnostics
           that have such a path associated with them.

           KIND is none, separate-events, or inline-events, the default.

           none means to not print diagnostic paths.

           separate-events means to print a separate "note" diagnostic for each
           event within the diagnostic.  For example:

                   test.c:29:5: error: passing NULL as argument 1 to 'PyList_Append' which requires a non-NULL parameter
                   test.c:25:10: note: (1) when 'PyList_New' fails, returning NULL
                   test.c:27:3: note: (2) when 'i < count'
                   test.c:29:5: note: (3) when calling 'PyList_Append', passing NULL from (1) as argument 1

           inline-events means to print the events "inline" within the source
           code.  This view attempts to consolidate the events into runs of
           sufficiently-close events, printing them as labelled ranges within
           the source.

           For example, the same events as above might be printed as:

                     'test': events 1-3
                       |
                       |   25 |   list = PyList_New(0);
                       |      |          ^~~~~~~~~~~~~
                       |      |          |
                       |      |          (1) when 'PyList_New' fails, returning NULL
                       |   26 |
                       |   27 |   for (i = 0; i < count; i++) {
                       |      |   ~~~
                       |      |   |
                       |      |   (2) when 'i < count'
                       |   28 |     item = PyLong_FromLong(random());
                       |   29 |     PyList_Append(list, item);
                       |      |     ~~~~~~~~~~~~~~~~~~~~~~~~~
                       |      |     |
                       |      |     (3) when calling 'PyList_Append', passing NULL from (1) as argument 1
                       |

           Interprocedural control flow is shown by grouping the events by stack
           frame, and using indentation to show how stack frames are nested,
           pushed, and popped.

           For example:

                     'test': events 1-2
                       |
                       |  133 | {
                       |      | ^
                       |      | |
                       |      | (1) entering 'test'
                       |  134 |   boxed_int *obj = make_boxed_int (i);
                       |      |                    ~~~~~~~~~~~~~~~~~~
                       |      |                    |
                       |      |                    (2) calling 'make_boxed_int'
                       |
                       +--> 'make_boxed_int': events 3-4
                              |
                              |  120 | {
                              |      | ^
                              |      | |
                              |      | (3) entering 'make_boxed_int'
                              |  121 |   boxed_int *result = (boxed_int *)wrapped_malloc (sizeof (boxed_int));
                              |      |                                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                              |      |                                    |
                              |      |                                    (4) calling 'wrapped_malloc'
                              |
                              +--> 'wrapped_malloc': events 5-6
                                     |
                                     |    7 | {
                                     |      | ^
                                     |      | |
                                     |      | (5) entering 'wrapped_malloc'
                                     |    8 |   return malloc (size);
                                     |      |          ~~~~~~~~~~~~~
                                     |      |          |
                                     |      |          (6) calling 'malloc'
                                     |
                       <-------------+
                       |
                    'test': event 7
                       |
                       |  138 |   free_boxed_int (obj);
                       |      |   ^~~~~~~~~~~~~~~~~~~~
                       |      |   |
                       |      |   (7) calling 'free_boxed_int'
                       |
                   (etc)

       -fdiagnostics-show-path-depths
           This option provides additional information when printing control-
           flow paths associated with a diagnostic.

           If this is option is provided then the stack depth will be printed
           for each run of events within
           -fdiagnostics-path-format=separate-events.

           This is intended for use by GCC developers and plugin developers when
           debugging diagnostics that report interprocedural control flow.

       -fno-show-column
           Do not print column numbers in diagnostics.  This may be necessary if
           diagnostics are being scanned by a program that does not understand
           the column numbers, such as dejagnu.

       -fdiagnostics-column-unit=UNIT
           Select the units for the column number.  This affects traditional
           diagnostics (in the absence of -fno-show-column), as well as JSON
           format diagnostics if requested.

           The default UNIT, display, considers the number of display columns
           occupied by each character.  This may be larger than the number of
           bytes required to encode the character, in the case of tab
           characters, or it may be smaller, in the case of multibyte
           characters.  For example, the character "GREEK SMALL LETTER PI
           (U+03C0)" occupies one display column, and its UTF-8 encoding
           requires two bytes; the character "SLIGHTLY SMILING FACE (U+1F642)"
           occupies two display columns, and its UTF-8 encoding requires four
           bytes.

           Setting UNIT to byte changes the column number to the raw byte count
           in all cases, as was traditionally output by GCC prior to version
           11.1.0.

       -fdiagnostics-column-origin=ORIGIN
           Select the origin for column numbers, i.e. the column number assigned
           to the first column.  The default value of 1 corresponds to
           traditional GCC behavior and to the GNU style guide.  Some utilities
           may perform better with an origin of 0; any non-negative value may be
           specified.

       -fdiagnostics-format=FORMAT
           Select a different format for printing diagnostics.  FORMAT is text
           or json.  The default is text.

           The json format consists of a top-level JSON array containing JSON
           objects representing the diagnostics.

           The JSON is emitted as one line, without formatting; the examples
           below have been formatted for clarity.

           Diagnostics can have child diagnostics.  For example, this error and
           note:

                   misleading-indentation.c:15:3: warning: this 'if' clause does not
                     guard... [-Wmisleading-indentation]
                      15 |   if (flag)
                         |   ^~
                   misleading-indentation.c:17:5: note: ...this statement, but the latter
                     is misleadingly indented as if it were guarded by the 'if'
                      17 |     y = 2;
                         |     ^

           might be printed in JSON form (after formatting) like this:

                   [
                       {
                           "kind": "warning",
                           "locations": [
                               {
                                   "caret": {
                                       "display-column": 3,
                                       "byte-column": 3,
                                       "column": 3,
                                       "file": "misleading-indentation.c",
                                       "line": 15
                                   },
                                   "finish": {
                                       "display-column": 4,
                                       "byte-column": 4,
                                       "column": 4,
                                       "file": "misleading-indentation.c",
                                       "line": 15
                                   }
                               }
                           ],
                           "message": "this \u2018if\u2019 clause does not guard...",
                           "option": "-Wmisleading-indentation",
                           "option_url": "https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wmisleading-indentation",
                           "children": [
                               {
                                   "kind": "note",
                                   "locations": [
                                       {
                                           "caret": {
                                               "display-column": 5,
                                               "byte-column": 5,
                                               "column": 5,
                                               "file": "misleading-indentation.c",
                                               "line": 17
                                           }
                                       }
                                   ],
                                   "message": "...this statement, but the latter is ..."
                               }
                           ]
                           "column-origin": 1,
                       },
                       ...
                   ]

           where the "note" is a child of the "warning".

           A diagnostic has a "kind".  If this is "warning", then there is an
           "option" key describing the command-line option controlling the
           warning.

           A diagnostic can contain zero or more locations.  Each location has
           an optional "label" string and up to three positions within it: a
           "caret" position and optional "start" and "finish" positions.  A
           position is described by a "file" name, a "line" number, and three
           numbers indicating a column position:

           *   "display-column" counts display columns, accounting for tabs and
               multibyte characters.

           *   "byte-column" counts raw bytes.

           *   "column" is equal to one of the previous two, as dictated by the
               -fdiagnostics-column-unit option.

           All three columns are relative to the origin specified by
           -fdiagnostics-column-origin, which is typically equal to 1 but may be
           set, for instance, to 0 for compatibility with other utilities that
           number columns from 0.  The column origin is recorded in the JSON
           output in the "column-origin" tag.  In the remaining examples below,
           the extra column number outputs have been omitted for brevity.

           For example, this error:

                   bad-binary-ops.c:64:23: error: invalid operands to binary + (have 'S' {aka
                      'struct s'} and 'T' {aka 'struct t'})
                      64 |   return callee_4a () + callee_4b ();
                         |          ~~~~~~~~~~~~ ^ ~~~~~~~~~~~~
                         |          |              |
                         |          |              T {aka struct t}
                         |          S {aka struct s}

           has three locations.  Its primary location is at the "+" token at
           column 23.  It has two secondary locations, describing the left and
           right-hand sides of the expression, which have labels.  It might be
           printed in JSON form as:

                       {
                           "children": [],
                           "kind": "error",
                           "locations": [
                               {
                                   "caret": {
                                       "column": 23, "file": "bad-binary-ops.c", "line": 64
                                   }
                               },
                               {
                                   "caret": {
                                       "column": 10, "file": "bad-binary-ops.c", "line": 64
                                   },
                                   "finish": {
                                       "column": 21, "file": "bad-binary-ops.c", "line": 64
                                   },
                                   "label": "S {aka struct s}"
                               },
                               {
                                   "caret": {
                                       "column": 25, "file": "bad-binary-ops.c", "line": 64
                                   },
                                   "finish": {
                                       "column": 36, "file": "bad-binary-ops.c", "line": 64
                                   },
                                   "label": "T {aka struct t}"
                               }
                           ],
                           "message": "invalid operands to binary + ..."
                       }

           If a diagnostic contains fix-it hints, it has a "fixits" array,
           consisting of half-open intervals, similar to the output of
           -fdiagnostics-parseable-fixits.  For example, this diagnostic with a
           replacement fix-it hint:

                   demo.c:8:15: error: 'struct s' has no member named 'colour'; did you
                     mean 'color'?
                       8 |   return ptr->colour;
                         |               ^~~~~~
                         |               color

           might be printed in JSON form as:

                       {
                           "children": [],
                           "fixits": [
                               {
                                   "next": {
                                       "column": 21,
                                       "file": "demo.c",
                                       "line": 8
                                   },
                                   "start": {
                                       "column": 15,
                                       "file": "demo.c",
                                       "line": 8
                                   },
                                   "string": "color"
                               }
                           ],
                           "kind": "error",
                           "locations": [
                               {
                                   "caret": {
                                       "column": 15,
                                       "file": "demo.c",
                                       "line": 8
                                   },
                                   "finish": {
                                       "column": 20,
                                       "file": "demo.c",
                                       "line": 8
                                   }
                               }
                           ],
                           "message": "\u2018struct s\u2019 has no member named ..."
                       }

           where the fix-it hint suggests replacing the text from "start" up to
           but not including "next" with "string"'s value.  Deletions are
           expressed via an empty value for "string", insertions by having
           "start" equal "next".

           If the diagnostic has a path of control-flow events associated with
           it, it has a "path" array of objects representing the events.  Each
           event object has a "description" string, a "location" object, along
           with a "function" string and a "depth" number for representing
           interprocedural paths.  The "function" represents the current
           function at that event, and the "depth" represents the stack depth
           relative to some baseline: the higher, the more frames are within the
           stack.

           For example, the intraprocedural example shown for
           -fdiagnostics-path-format= might have this JSON for its path:

                       "path": [
                           {
                               "depth": 0,
                               "description": "when 'PyList_New' fails, returning NULL",
                               "function": "test",
                               "location": {
                                   "column": 10,
                                   "file": "test.c",
                                   "line": 25
                               }
                           },
                           {
                               "depth": 0,
                               "description": "when 'i < count'",
                               "function": "test",
                               "location": {
                                   "column": 3,
                                   "file": "test.c",
                                   "line": 27
                               }
                           },
                           {
                               "depth": 0,
                               "description": "when calling 'PyList_Append', passing NULL from (1) as argument 1",
                               "function": "test",
                               "location": {
                                   "column": 5,
                                   "file": "test.c",
                                   "line": 29
                               }
                           }
                       ]

   Options to Request or Suppress Warnings
       Warnings are diagnostic messages that report constructions that are not
       inherently erroneous but that are risky or suggest there may have been an
       error.

       The following language-independent options do not enable specific
       warnings but control the kinds of diagnostics produced by GCC.

       -fsyntax-only
           Check the code for syntax errors, but don't do anything beyond that.

       -fmax-errors=n
           Limits the maximum number of error messages to n, at which point GCC
           bails out rather than attempting to continue processing the source
           code.  If n is 0 (the default), there is no limit on the number of
           error messages produced.  If -Wfatal-errors is also specified, then
           -Wfatal-errors takes precedence over this option.

       -w  Inhibit all warning messages.

       -Werror
           Make all warnings into errors.

       -Werror=
           Make the specified warning into an error.  The specifier for a
           warning is appended; for example -Werror=switch turns the warnings
           controlled by -Wswitch into errors.  This switch takes a negative
           form, to be used to negate -Werror for specific warnings; for example
           -Wno-error=switch makes -Wswitch warnings not be errors, even when
           -Werror is in effect.

           The warning message for each controllable warning includes the option
           that controls the warning.  That option can then be used with
           -Werror= and -Wno-error= as described above.  (Printing of the option
           in the warning message can be disabled using the
           -fno-diagnostics-show-option flag.)

           Note that specifying -Werror=foo automatically implies -Wfoo.
           However, -Wno-error=foo does not imply anything.

       -Wfatal-errors
           This option causes the compiler to abort compilation on the first
           error occurred rather than trying to keep going and printing further
           error messages.

       You can request many specific warnings with options beginning with -W,
       for example -Wimplicit to request warnings on implicit declarations.
       Each of these specific warning options also has a negative form beginning
       -Wno- to turn off warnings; for example, -Wno-implicit.  This manual
       lists only one of the two forms, whichever is not the default.  For
       further language-specific options also refer to C++ Dialect Options and
       Objective-C and Objective-C++ Dialect Options.  Additional warnings can
       be produced by enabling the static analyzer;

       Some options, such as -Wall and -Wextra, turn on other options, such as
       -Wunused, which may turn on further options, such as -Wunused-value. The
       combined effect of positive and negative forms is that more specific
       options have priority over less specific ones, independently of their
       position in the command-line. For options of the same specificity, the
       last one takes effect. Options enabled or disabled via pragmas take
       effect as if they appeared at the end of the command-line.

       When an unrecognized warning option is requested (e.g.,
       -Wunknown-warning), GCC emits a diagnostic stating that the option is not
       recognized.  However, if the -Wno- form is used, the behavior is slightly
       different: no diagnostic is produced for -Wno-unknown-warning unless
       other diagnostics are being produced.  This allows the use of new -Wno-
       options with old compilers, but if something goes wrong, the compiler
       warns that an unrecognized option is present.

       The effectiveness of some warnings depends on optimizations also being
       enabled. For example -Wsuggest-final-types is more effective with link-
       time optimization and -Wmaybe-uninitialized does not warn at all unless
       optimization is enabled.

       -Wpedantic
       -pedantic
           Issue all the warnings demanded by strict ISO C and ISO C++; reject
           all programs that use forbidden extensions, and some other programs
           that do not follow ISO C and ISO C++.  For ISO C, follows the version
           of the ISO C standard specified by any -std option used.

           Valid ISO C and ISO C++ programs should compile properly with or
           without this option (though a rare few require -ansi or a -std option
           specifying the required version of ISO C).  However, without this
           option, certain GNU extensions and traditional C and C++ features are
           supported as well.  With this option, they are rejected.

           -Wpedantic does not cause warning messages for use of the alternate
           keywords whose names begin and end with __.  This alternate format
           can also be used to disable warnings for non-ISO __intN types, i.e.
           __intN__.  Pedantic warnings are also disabled in the expression that
           follows "__extension__".  However, only system header files should
           use these escape routes; application programs should avoid them.

           Some users try to use -Wpedantic to check programs for strict ISO C
           conformance.  They soon find that it does not do quite what they
           want: it finds some non-ISO practices, but not all---only those for
           which ISO C requires a diagnostic, and some others for which
           diagnostics have been added.

           A feature to report any failure to conform to ISO C might be useful
           in some instances, but would require considerable additional work and
           would be quite different from -Wpedantic.  We don't have plans to
           support such a feature in the near future.

           Where the standard specified with -std represents a GNU extended
           dialect of C, such as gnu90 or gnu99, there is a corresponding base
           standard, the version of ISO C on which the GNU extended dialect is
           based.  Warnings from -Wpedantic are given where they are required by
           the base standard.  (It does not make sense for such warnings to be
           given only for features not in the specified GNU C dialect, since by
           definition the GNU dialects of C include all features the compiler
           supports with the given option, and there would be nothing to warn
           about.)

       -pedantic-errors
           Give an error whenever the base standard (see -Wpedantic) requires a
           diagnostic, in some cases where there is undefined behavior at
           compile-time and in some other cases that do not prevent compilation
           of programs that are valid according to the standard. This is not
           equivalent to -Werror=pedantic, since there are errors enabled by
           this option and not enabled by the latter and vice versa.

       -Wall
           This enables all the warnings about constructions that some users
           consider questionable, and that are easy to avoid (or modify to
           prevent the warning), even in conjunction with macros.  This also
           enables some language-specific warnings described in C++ Dialect
           Options and Objective-C and Objective-C++ Dialect Options.

           -Wall turns on the following warning flags:

           -Waddress -Warray-bounds=1 (only with -O2) -Warray-parameter=2 (C and
           Objective-C only) -Wbool-compare -Wbool-operation -Wc++11-compat
           -Wc++14-compat -Wcatch-value (C++ and Objective-C++ only)
           -Wchar-subscripts -Wcomment -Wduplicate-decl-specifier (C and
           Objective-C only) -Wenum-compare (in C/ObjC; this is on by default in
           C++) -Wformat -Wformat-overflow -Wformat-truncation
           -Wint-in-bool-context -Wimplicit (C and Objective-C only)
           -Wimplicit-int (C and Objective-C only)
           -Wimplicit-function-declaration (C and Objective-C only) -Winit-self
           (only for C++) -Wlogical-not-parentheses -Wmain (only for C/ObjC and
           unless -ffreestanding) -Wmaybe-uninitialized -Wmemset-elt-size
           -Wmemset-transposed-args -Wmisleading-indentation (only for C/C++)
           -Wmissing-attributes -Wmissing-braces (only for C/ObjC)
           -Wmultistatement-macros -Wnarrowing (only for C++) -Wnonnull
           -Wnonnull-compare -Wopenmp-simd -Wparentheses -Wpessimizing-move
           (only for C++) -Wpointer-sign -Wrange-loop-construct (only for C++)
           -Wreorder -Wrestrict -Wreturn-type -Wsequence-point -Wsign-compare
           (only in C++) -Wsizeof-array-div -Wsizeof-pointer-div
           -Wsizeof-pointer-memaccess -Wstrict-aliasing -Wstrict-overflow=1
           -Wswitch -Wtautological-compare -Wtrigraphs -Wuninitialized
           -Wunknown-pragmas -Wunused-function -Wunused-label -Wunused-value
           -Wunused-variable -Wvla-parameter (C and Objective-C only)
           -Wvolatile-register-var -Wzero-length-bounds

           Note that some warning flags are not implied by -Wall.  Some of them
           warn about constructions that users generally do not consider
           questionable, but which occasionally you might wish to check for;
           others warn about constructions that are necessary or hard to avoid
           in some cases, and there is no simple way to modify the code to
           suppress the warning. Some of them are enabled by -Wextra but many of
           them must be enabled individually.

       -Wextra
           This enables some extra warning flags that are not enabled by -Wall.
           (This option used to be called -W.  The older name is still
           supported, but the newer name is more descriptive.)

           -Wclobbered -Wcast-function-type -Wdeprecated-copy (C++ only)
           -Wempty-body -Wenum-conversion (C only) -Wignored-qualifiers
           -Wimplicit-fallthrough=3 -Wmissing-field-initializers
           -Wmissing-parameter-type (C only) -Wold-style-declaration (C only)
           -Woverride-init -Wsign-compare (C only) -Wstring-compare
           -Wredundant-move (only for C++) -Wtype-limits -Wuninitialized
           -Wshift-negative-value (in C++03 and in C99 and newer)
           -Wunused-parameter (only with -Wunused or -Wall)
           -Wunused-but-set-parameter (only with -Wunused or -Wall)

           The option -Wextra also prints warning messages for the following
           cases:

           *   A pointer is compared against integer zero with "<", "<=", ">",
               or ">=".

           *   (C++ only) An enumerator and a non-enumerator both appear in a
               conditional expression.

           *   (C++ only) Ambiguous virtual bases.

           *   (C++ only) Subscripting an array that has been declared
               "register".

           *   (C++ only) Taking the address of a variable that has been
               declared "register".

           *   (C++ only) A base class is not initialized in the copy
               constructor of a derived class.

       -Wabi (C, Objective-C, C++ and Objective-C++ only)
           Warn about code affected by ABI changes.  This includes code that may
           not be compatible with the vendor-neutral C++ ABI as well as the
           psABI for the particular target.

           Since G++ now defaults to updating the ABI with each major release,
           normally -Wabi warns only about C++ ABI compatibility problems if
           there is a check added later in a release series for an ABI issue
           discovered since the initial release.  -Wabi warns about more things
           if an older ABI version is selected (with -fabi-version=n).

           -Wabi can also be used with an explicit version number to warn about
           C++ ABI compatibility with a particular -fabi-version level, e.g.
           -Wabi=2 to warn about changes relative to -fabi-version=2.

           If an explicit version number is provided and -fabi-compat-version is
           not specified, the version number from this option is used for
           compatibility aliases.  If no explicit version number is provided
           with this option, but -fabi-compat-version is specified, that version
           number is used for C++ ABI warnings.

           Although an effort has been made to warn about all such cases, there
           are probably some cases that are not warned about, even though G++ is
           generating incompatible code.  There may also be cases where warnings
           are emitted even though the code that is generated is compatible.

           You should rewrite your code to avoid these warnings if you are
           concerned about the fact that code generated by G++ may not be binary
           compatible with code generated by other compilers.

           Known incompatibilities in -fabi-version=2 (which was the default
           from GCC 3.4 to 4.9) include:

           *   A template with a non-type template parameter of reference type
               was mangled incorrectly:

                       extern int N;
                       template <int &> struct S {};
                       void n (S<N>) {2}

               This was fixed in -fabi-version=3.

           *   SIMD vector types declared using "__attribute ((vector_size))"
               were mangled in a non-standard way that does not allow for
               overloading of functions taking vectors of different sizes.

               The mangling was changed in -fabi-version=4.

           *   "__attribute ((const))" and "noreturn" were mangled as type
               qualifiers, and "decltype" of a plain declaration was folded
               away.

               These mangling issues were fixed in -fabi-version=5.

           *   Scoped enumerators passed as arguments to a variadic function are
               promoted like unscoped enumerators, causing "va_arg" to complain.
               On most targets this does not actually affect the parameter
               passing ABI, as there is no way to pass an argument smaller than
               "int".

               Also, the ABI changed the mangling of template argument packs,
               "const_cast", "static_cast", prefix increment/decrement, and a
               class scope function used as a template argument.

               These issues were corrected in -fabi-version=6.

           *   Lambdas in default argument scope were mangled incorrectly, and
               the ABI changed the mangling of "nullptr_t".

               These issues were corrected in -fabi-version=7.

           *   When mangling a function type with function-cv-qualifiers, the
               un-qualified function type was incorrectly treated as a
               substitution candidate.

               This was fixed in -fabi-version=8, the default for GCC 5.1.

           *   "decltype(nullptr)" incorrectly had an alignment of 1, leading to
               unaligned accesses.  Note that this did not affect the ABI of a
               function with a "nullptr_t" parameter, as parameters have a
               minimum alignment.

               This was fixed in -fabi-version=9, the default for GCC 5.2.

           *   Target-specific attributes that affect the identity of a type,
               such as ia32 calling conventions on a function type (stdcall,
               regparm, etc.), did not affect the mangled name, leading to name
               collisions when function pointers were used as template
               arguments.

               This was fixed in -fabi-version=10, the default for GCC 6.1.

           This option also enables warnings about psABI-related changes.  The
           known psABI changes at this point include:

           *   For SysV/x86-64, unions with "long double" members are passed in
               memory as specified in psABI.  Prior to GCC 4.4, this was not the
               case.  For example:

                       union U {
                         long double ld;
                         int i;
                       };

               "union U" is now always passed in memory.

       -Wchar-subscripts
           Warn if an array subscript has type "char".  This is a common cause
           of error, as programmers often forget that this type is signed on
           some machines.  This warning is enabled by -Wall.

       -Wno-coverage-mismatch
           Warn if feedback profiles do not match when using the -fprofile-use
           option.  If a source file is changed between compiling with
           -fprofile-generate and with -fprofile-use, the files with the profile
           feedback can fail to match the source file and GCC cannot use the
           profile feedback information.  By default, this warning is enabled
           and is treated as an error.  -Wno-coverage-mismatch can be used to
           disable the warning or -Wno-error=coverage-mismatch can be used to
           disable the error.  Disabling the error for this warning can result
           in poorly optimized code and is useful only in the case of very minor
           changes such as bug fixes to an existing code-base.  Completely
           disabling the warning is not recommended.

       -Wno-cpp
           (C, Objective-C, C++, Objective-C++ and Fortran only) Suppress
           warning messages emitted by "#warning" directives.

       -Wdouble-promotion (C, C++, Objective-C and Objective-C++ only)
           Give a warning when a value of type "float" is implicitly promoted to
           "double".  CPUs with a 32-bit "single-precision" floating-point unit
           implement "float" in hardware, but emulate "double" in software.  On
           such a machine, doing computations using "double" values is much more
           expensive because of the overhead required for software emulation.

           It is easy to accidentally do computations with "double" because
           floating-point literals are implicitly of type "double".  For
           example, in:

                   float area(float radius)
                   {
                      return 3.14159 * radius * radius;
                   }

           the compiler performs the entire computation with "double" because
           the floating-point literal is a "double".

       -Wduplicate-decl-specifier (C and Objective-C only)
           Warn if a declaration has duplicate "const", "volatile", "restrict"
           or "_Atomic" specifier.  This warning is enabled by -Wall.

       -Wformat
       -Wformat=n
           Check calls to "printf" and "scanf", etc., to make sure that the
           arguments supplied have types appropriate to the format string
           specified, and that the conversions specified in the format string
           make sense.  This includes standard functions, and others specified
           by format attributes, in the "printf", "scanf", "strftime" and
           "strfmon" (an X/Open extension, not in the C standard) families (or
           other target-specific families).  Which functions are checked without
           format attributes having been specified depends on the standard
           version selected, and such checks of functions without the attribute
           specified are disabled by -ffreestanding or -fno-builtin.

           The formats are checked against the format features supported by GNU
           libc version 2.2.  These include all ISO C90 and C99 features, as
           well as features from the Single Unix Specification and some BSD and
           GNU extensions.  Other library implementations may not support all
           these features; GCC does not support warning about features that go
           beyond a particular library's limitations.  However, if -Wpedantic is
           used with -Wformat, warnings are given about format features not in
           the selected standard version (but not for "strfmon" formats, since
           those are not in any version of the C standard).

           -Wformat=1
           -Wformat
               Option -Wformat is equivalent to -Wformat=1, and -Wno-format is
               equivalent to -Wformat=0.  Since -Wformat also checks for null
               format arguments for several functions, -Wformat also implies
               -Wnonnull.  Some aspects of this level of format checking can be
               disabled by the options: -Wno-format-contains-nul,
               -Wno-format-extra-args, and -Wno-format-zero-length.  -Wformat is
               enabled by -Wall.

           -Wformat=2
               Enable -Wformat plus additional format checks.  Currently
               equivalent to -Wformat -Wformat-nonliteral -Wformat-security
               -Wformat-y2k.

       -Wno-format-contains-nul
           If -Wformat is specified, do not warn about format strings that
           contain NUL bytes.

       -Wno-format-extra-args
           If -Wformat is specified, do not warn about excess arguments to a
           "printf" or "scanf" format function.  The C standard specifies that
           such arguments are ignored.

           Where the unused arguments lie between used arguments that are
           specified with $ operand number specifications, normally warnings are
           still given, since the implementation could not know what type to
           pass to "va_arg" to skip the unused arguments.  However, in the case
           of "scanf" formats, this option suppresses the warning if the unused
           arguments are all pointers, since the Single Unix Specification says
           that such unused arguments are allowed.

       -Wformat-overflow
       -Wformat-overflow=level
           Warn about calls to formatted input/output functions such as
           "sprintf" and "vsprintf" that might overflow the destination buffer.
           When the exact number of bytes written by a format directive cannot
           be determined at compile-time it is estimated based on heuristics
           that depend on the level argument and on optimization.  While
           enabling optimization will in most cases improve the accuracy of the
           warning, it may also result in false positives.

           -Wformat-overflow
           -Wformat-overflow=1
               Level 1 of -Wformat-overflow enabled by -Wformat employs a
               conservative approach that warns only about calls that most
               likely overflow the buffer.  At this level, numeric arguments to
               format directives with unknown values are assumed to have the
               value of one, and strings of unknown length to be empty.  Numeric
               arguments that are known to be bounded to a subrange of their
               type, or string arguments whose output is bounded either by their
               directive's precision or by a finite set of string literals, are
               assumed to take on the value within the range that results in the
               most bytes on output.  For example, the call to "sprintf" below
               is diagnosed because even with both a and b equal to zero, the
               terminating NUL character ('\0') appended by the function to the
               destination buffer will be written past its end.  Increasing the
               size of the buffer by a single byte is sufficient to avoid the
               warning, though it may not be sufficient to avoid the overflow.

                       void f (int a, int b)
                       {
                         char buf [13];
                         sprintf (buf, "a = %i, b = %i\n", a, b);
                       }

           -Wformat-overflow=2
               Level 2 warns also about calls that might overflow the
               destination buffer given an argument of sufficient length or
               magnitude.  At level 2, unknown numeric arguments are assumed to
               have the minimum representable value for signed types with a
               precision greater than 1, and the maximum representable value
               otherwise.  Unknown string arguments whose length cannot be
               assumed to be bounded either by the directive's precision, or by
               a finite set of string literals they may evaluate to, or the
               character array they may point to, are assumed to be 1 character
               long.

               At level 2, the call in the example above is again diagnosed, but
               this time because with a equal to a 32-bit "INT_MIN" the first %i
               directive will write some of its digits beyond the end of the
               destination buffer.  To make the call safe regardless of the
               values of the two variables, the size of the destination buffer
               must be increased to at least 34 bytes.  GCC includes the minimum
               size of the buffer in an informational note following the
               warning.

               An alternative to increasing the size of the destination buffer
               is to constrain the range of formatted values.  The maximum
               length of string arguments can be bounded by specifying the
               precision in the format directive.  When numeric arguments of
               format directives can be assumed to be bounded by less than the
               precision of their type, choosing an appropriate length modifier
               to the format specifier will reduce the required buffer size.
               For example, if a and b in the example above can be assumed to be
               within the precision of the "short int" type then using either
               the %hi format directive or casting the argument to "short"
               reduces the maximum required size of the buffer to 24 bytes.

                       void f (int a, int b)
                       {
                         char buf [23];
                         sprintf (buf, "a = %hi, b = %i\n", a, (short)b);
                       }

       -Wno-format-zero-length
           If -Wformat is specified, do not warn about zero-length formats.  The
           C standard specifies that zero-length formats are allowed.

       -Wformat-nonliteral
           If -Wformat is specified, also warn if the format string is not a
           string literal and so cannot be checked, unless the format function
           takes its format arguments as a "va_list".

       -Wformat-security
           If -Wformat is specified, also warn about uses of format functions
           that represent possible security problems.  At present, this warns
           about calls to "printf" and "scanf" functions where the format string
           is not a string literal and there are no format arguments, as in
           "printf (foo);".  This may be a security hole if the format string
           came from untrusted input and contains %n.  (This is currently a
           subset of what -Wformat-nonliteral warns about, but in future
           warnings may be added to -Wformat-security that are not included in
           -Wformat-nonliteral.)

       -Wformat-signedness
           If -Wformat is specified, also warn if the format string requires an
           unsigned argument and the argument is signed and vice versa.

       -Wformat-truncation
       -Wformat-truncation=level
           Warn about calls to formatted input/output functions such as
           "snprintf" and "vsnprintf" that might result in output truncation.
           When the exact number of bytes written by a format directive cannot
           be determined at compile-time it is estimated based on heuristics
           that depend on the level argument and on optimization.  While
           enabling optimization will in most cases improve the accuracy of the
           warning, it may also result in false positives.  Except as noted
           otherwise, the option uses the same logic -Wformat-overflow.

           -Wformat-truncation
           -Wformat-truncation=1
               Level 1 of -Wformat-truncation enabled by -Wformat employs a
               conservative approach that warns only about calls to bounded
               functions whose return value is unused and that will most likely
               result in output truncation.

           -Wformat-truncation=2
               Level 2 warns also about calls to bounded functions whose return
               value is used and that might result in truncation given an
               argument of sufficient length or magnitude.

       -Wformat-y2k
           If -Wformat is specified, also warn about "strftime" formats that may
           yield only a two-digit year.

       -Wnonnull
           Warn about passing a null pointer for arguments marked as requiring a
           non-null value by the "nonnull" function attribute.

           -Wnonnull is included in -Wall and -Wformat.  It can be disabled with
           the -Wno-nonnull option.

       -Wnonnull-compare
           Warn when comparing an argument marked with the "nonnull" function
           attribute against null inside the function.

           -Wnonnull-compare is included in -Wall.  It can be disabled with the
           -Wno-nonnull-compare option.

       -Wnull-dereference
           Warn if the compiler detects paths that trigger erroneous or
           undefined behavior due to dereferencing a null pointer.  This option
           is only active when -fdelete-null-pointer-checks is active, which is
           enabled by optimizations in most targets.  The precision of the
           warnings depends on the optimization options used.

       -Winit-self (C, C++, Objective-C and Objective-C++ only)
           Warn about uninitialized variables that are initialized with
           themselves.  Note this option can only be used with the
           -Wuninitialized option.

           For example, GCC warns about "i" being uninitialized in the following
           snippet only when -Winit-self has been specified:

                   int f()
                   {
                     int i = i;
                     return i;
                   }

           This warning is enabled by -Wall in C++.

       -Wno-implicit-int (C and Objective-C only)
           This option controls warnings when a declaration does not specify a
           type.  This warning is enabled by default in C99 and later dialects
           of C, and also by -Wall.

       -Wno-implicit-function-declaration (C and Objective-C only)
           This option controls warnings when a function is used before being
           declared.  This warning is enabled by default in C99 and later
           dialects of C, and also by -Wall.  The warning is made into an error
           by -pedantic-errors.

       -Wimplicit (C and Objective-C only)
           Same as -Wimplicit-int and -Wimplicit-function-declaration.  This
           warning is enabled by -Wall.

       -Wimplicit-fallthrough
           -Wimplicit-fallthrough is the same as -Wimplicit-fallthrough=3 and
           -Wno-implicit-fallthrough is the same as -Wimplicit-fallthrough=0.

       -Wimplicit-fallthrough=n
           Warn when a switch case falls through.  For example:

                   switch (cond)
                     {
                     case 1:
                       a = 1;
                       break;
                     case 2:
                       a = 2;
                     case 3:
                       a = 3;
                       break;
                     }

           This warning does not warn when the last statement of a case cannot
           fall through, e.g. when there is a return statement or a call to
           function declared with the noreturn attribute.
           -Wimplicit-fallthrough= also takes into account control flow
           statements, such as ifs, and only warns when appropriate.  E.g.

                   switch (cond)
                     {
                     case 1:
                       if (i > 3) {
                         bar (5);
                         break;
                       } else if (i < 1) {
                         bar (0);
                       } else
                         return;
                     default:
                       ...
                     }

           Since there are occasions where a switch case fall through is
           desirable, GCC provides an attribute, "__attribute__
           ((fallthrough))", that is to be used along with a null statement to
           suppress this warning that would normally occur:

                   switch (cond)
                     {
                     case 1:
                       bar (0);
                       __attribute__ ((fallthrough));
                     default:
                       ...
                     }

           C++17 provides a standard way to suppress the -Wimplicit-fallthrough
           warning using "[[fallthrough]];" instead of the GNU attribute.  In
           C++11 or C++14 users can use "[[gnu::fallthrough]];", which is a GNU
           extension.  Instead of these attributes, it is also possible to add a
           fallthrough comment to silence the warning.  The whole body of the C
           or C++ style comment should match the given regular expressions
           listed below.  The option argument n specifies what kind of comments
           are accepted:

           *<-Wimplicit-fallthrough=0 disables the warning altogether.>
           *<-Wimplicit-fallthrough=1 matches ".*" regular>
               expression, any comment is used as fallthrough comment.

           *<-Wimplicit-fallthrough=2 case insensitively matches>
               ".*falls?[ \t-]*thr(ough|u).*" regular expression.

           *<-Wimplicit-fallthrough=3 case sensitively matches one of the>
               following regular expressions:

               *<"-fallthrough">
               *<"@fallthrough@">
               *<"lint -fallthrough[ \t]*">
               *<"[ \t.!]*(ELSE,? |INTENTIONAL(LY)? )?FALL(S | |-)?THR(OUGH|U)[
               \t.!]*(-[^\n\r]*)?">
               *<"[ \t.!]*(Else,? |Intentional(ly)? )?Fall((s |
               |-)[Tt]|t)hr(ough|u)[ \t.!]*(-[^\n\r]*)?">
               *<"[ \t.!]*([Ee]lse,? |[Ii]ntentional(ly)? )?fall(s |
               |-)?thr(ough|u)[ \t.!]*(-[^\n\r]*)?">
           *<-Wimplicit-fallthrough=4 case sensitively matches one of the>
               following regular expressions:

               *<"-fallthrough">
               *<"@fallthrough@">
               *<"lint -fallthrough[ \t]*">
               *<"[ \t]*FALLTHR(OUGH|U)[ \t]*">
           *<-Wimplicit-fallthrough=5 doesn't recognize any comments as>
               fallthrough comments, only attributes disable the warning.

           The comment needs to be followed after optional whitespace and other
           comments by "case" or "default" keywords or by a user label that
           precedes some "case" or "default" label.

                   switch (cond)
                     {
                     case 1:
                       bar (0);
                       /* FALLTHRU */
                     default:
                       ...
                     }

           The -Wimplicit-fallthrough=3 warning is enabled by -Wextra.

       -Wno-if-not-aligned (C, C++, Objective-C and Objective-C++ only)
           Control if warnings triggered by the "warn_if_not_aligned" attribute
           should be issued.  These warnings are enabled by default.

       -Wignored-qualifiers (C and C++ only)
           Warn if the return type of a function has a type qualifier such as
           "const".  For ISO C such a type qualifier has no effect, since the
           value returned by a function is not an lvalue.  For C++, the warning
           is only emitted for scalar types or "void".  ISO C prohibits
           qualified "void" return types on function definitions, so such return
           types always receive a warning even without this option.

           This warning is also enabled by -Wextra.

       -Wno-ignored-attributes (C and C++ only)
           This option controls warnings when an attribute is ignored.  This is
           different from the -Wattributes option in that it warns whenever the
           compiler decides to drop an attribute, not that the attribute is
           either unknown, used in a wrong place, etc.  This warning is enabled
           by default.

       -Wmain
           Warn if the type of "main" is suspicious.  "main" should be a
           function with external linkage, returning int, taking either zero
           arguments, two, or three arguments of appropriate types.  This
           warning is enabled by default in C++ and is enabled by either -Wall
           or -Wpedantic.

       -Wmisleading-indentation (C and C++ only)
           Warn when the indentation of the code does not reflect the block
           structure.  Specifically, a warning is issued for "if", "else",
           "while", and "for" clauses with a guarded statement that does not use
           braces, followed by an unguarded statement with the same indentation.

           In the following example, the call to "bar" is misleadingly indented
           as if it were guarded by the "if" conditional.

                     if (some_condition ())
                       foo ();
                       bar ();  /* Gotcha: this is not guarded by the "if".  */

           In the case of mixed tabs and spaces, the warning uses the -ftabstop=
           option to determine if the statements line up (defaulting to 8).

           The warning is not issued for code involving multiline preprocessor
           logic such as the following example.

                     if (flagA)
                       foo (0);
                   #if SOME_CONDITION_THAT_DOES_NOT_HOLD
                     if (flagB)
                   #endif
                       foo (1);

           The warning is not issued after a "#line" directive, since this
           typically indicates autogenerated code, and no assumptions can be
           made about the layout of the file that the directive references.

           This warning is enabled by -Wall in C and C++.

       -Wmissing-attributes
           Warn when a declaration of a function is missing one or more
           attributes that a related function is declared with and whose absence
           may adversely affect the correctness or efficiency of generated code.
           For example, the warning is issued for declarations of aliases that
           use attributes to specify less restrictive requirements than those of
           their targets.  This typically represents a potential optimization
           opportunity.  By contrast, the -Wattribute-alias=2 option controls
           warnings issued when the alias is more restrictive than the target,
           which could lead to incorrect code generation.  Attributes considered
           include "alloc_align", "alloc_size", "cold", "const", "hot", "leaf",
           "malloc", "nonnull", "noreturn", "nothrow", "pure",
           "returns_nonnull", and "returns_twice".

           In C++, the warning is issued when an explicit specialization of a
           primary template declared with attribute "alloc_align", "alloc_size",
           "assume_aligned", "format", "format_arg", "malloc", or "nonnull" is
           declared without it.  Attributes "deprecated", "error", and "warning"
           suppress the warning..

           You can use the "copy" attribute to apply the same set of attributes
           to a declaration as that on another declaration without explicitly
           enumerating the attributes. This attribute can be applied to
           declarations of functions, variables, or types.

           -Wmissing-attributes is enabled by -Wall.

           For example, since the declaration of the primary function template
           below makes use of both attribute "malloc" and "alloc_size" the
           declaration of the explicit specialization of the template is
           diagnosed because it is missing one of the attributes.

                   template <class T>
                   T* __attribute__ ((malloc, alloc_size (1)))
                   allocate (size_t);

                   template <>
                   void* __attribute__ ((malloc))   // missing alloc_size
                   allocate<void> (size_t);

       -Wmissing-braces
           Warn if an aggregate or union initializer is not fully bracketed.  In
           the following example, the initializer for "a" is not fully
           bracketed, but that for "b" is fully bracketed.

                   int a[2][2] = { 0, 1, 2, 3 };
                   int b[2][2] = { { 0, 1 }, { 2, 3 } };

           This warning is enabled by -Wall.

       -Wmissing-include-dirs (C, C++, Objective-C and Objective-C++ only)
           Warn if a user-supplied include directory does not exist.

       -Wno-missing-profile
           This option controls warnings if feedback profiles are missing when
           using the -fprofile-use option.  This option diagnoses those cases
           where a new function or a new file is added between compiling with
           -fprofile-generate and with -fprofile-use, without regenerating the
           profiles.  In these cases, the profile feedback data files do not
           contain any profile feedback information for the newly added function
           or file respectively.  Also, in the case when profile count data
           (.gcda) files are removed, GCC cannot use any profile feedback
           information.  In all these cases, warnings are issued to inform you
           that a profile generation step is due.  Ignoring the warning can
           result in poorly optimized code.  -Wno-missing-profile can be used to
           disable the warning, but this is not recommended and should be done
           only when non-existent profile data is justified.

       -Wno-mismatched-dealloc
           Warn for calls to deallocation functions with pointer arguments
           returned from from allocations functions for which the former isn't a
           suitable deallocator.  A pair of functions can be associated as
           matching allocators and deallocators by use of attribute "malloc".
           Unless disabled by the -fno-builtin option the standard functions
           "calloc", "malloc", "realloc", and "free", as well as the
           corresponding forms of C++ "operator new" and "operator delete" are
           implicitly associated as matching allocators and deallocators.  In
           the following example "mydealloc" is the deallocator for pointers
           returned from "myalloc".

                   void mydealloc (void*);

                   __attribute__ ((malloc (mydealloc, 1))) void*
                   myalloc (size_t);

                   void f (void)
                   {
                     void *p = myalloc (32);
                     // ...use p...
                     free (p);   // warning: not a matching deallocator for myalloc
                     mydealloc (p);   // ok
                   }

           In C++, the related option -Wmismatched-new-delete diagnoses
           mismatches involving either "operator new" or "operator delete".

           Option -Wmismatched-dealloc is enabled by default.

       -Wmultistatement-macros
           Warn about unsafe multiple statement macros that appear to be guarded
           by a clause such as "if", "else", "for", "switch", or "while", in
           which only the first statement is actually guarded after the macro is
           expanded.

           For example:

                   #define DOIT x++; y++
                   if (c)
                     DOIT;

           will increment "y" unconditionally, not just when "c" holds.  The can
           usually be fixed by wrapping the macro in a do-while loop:

                   #define DOIT do { x++; y++; } while (0)
                   if (c)
                     DOIT;

           This warning is enabled by -Wall in C and C++.

       -Wparentheses
           Warn if parentheses are omitted in certain contexts, such as when
           there is an assignment in a context where a truth value is expected,
           or when operators are nested whose precedence people often get
           confused about.

           Also warn if a comparison like "x<=y<=z" appears; this is equivalent
           to "(x<=y ? 1 : 0) <= z", which is a different interpretation from
           that of ordinary mathematical notation.

           Also warn for dangerous uses of the GNU extension to "?:" with
           omitted middle operand. When the condition in the "?": operator is a
           boolean expression, the omitted value is always 1.  Often programmers
           expect it to be a value computed inside the conditional expression
           instead.

           For C++ this also warns for some cases of unnecessary parentheses in
           declarations, which can indicate an attempt at a function call
           instead of a declaration:

                   {
                     // Declares a local variable called mymutex.
                     std::unique_lock<std::mutex> (mymutex);
                     // User meant std::unique_lock<std::mutex> lock (mymutex);
                   }

           This warning is enabled by -Wall.

       -Wsequence-point
           Warn about code that may have undefined semantics because of
           violations of sequence point rules in the C and C++ standards.

           The C and C++ standards define the order in which expressions in a
           C/C++ program are evaluated in terms of sequence points, which
           represent a partial ordering between the execution of parts of the
           program: those executed before the sequence point, and those executed
           after it.  These occur after the evaluation of a full expression (one
           which is not part of a larger expression), after the evaluation of
           the first operand of a "&&", "||", "? :" or "," (comma) operator,
           before a function is called (but after the evaluation of its
           arguments and the expression denoting the called function), and in
           certain other places.  Other than as expressed by the sequence point
           rules, the order of evaluation of subexpressions of an expression is
           not specified.  All these rules describe only a partial order rather
           than a total order, since, for example, if two functions are called
           within one expression with no sequence point between them, the order
           in which the functions are called is not specified.  However, the
           standards committee have ruled that function calls do not overlap.

           It is not specified when between sequence points modifications to the
           values of objects take effect.  Programs whose behavior depends on
           this have undefined behavior; the C and C++ standards specify that
           "Between the previous and next sequence point an object shall have
           its stored value modified at most once by the evaluation of an
           expression.  Furthermore, the prior value shall be read only to
           determine the value to be stored.".  If a program breaks these rules,
           the results on any particular implementation are entirely
           unpredictable.

           Examples of code with undefined behavior are "a = a++;", "a[n] =
           b[n++]" and "a[i++] = i;".  Some more complicated cases are not
           diagnosed by this option, and it may give an occasional false
           positive result, but in general it has been found fairly effective at
           detecting this sort of problem in programs.

           The C++17 standard will define the order of evaluation of operands in
           more cases: in particular it requires that the right-hand side of an
           assignment be evaluated before the left-hand side, so the above
           examples are no longer undefined.  But this option will still warn
           about them, to help people avoid writing code that is undefined in C
           and earlier revisions of C++.

           The standard is worded confusingly, therefore there is some debate
           over the precise meaning of the sequence point rules in subtle cases.
           Links to discussions of the problem, including proposed formal
           definitions, may be found on the GCC readings page, at
           <http://gcc.gnu.org/readings.html>.

           This warning is enabled by -Wall for C and C++.

       -Wno-return-local-addr
           Do not warn about returning a pointer (or in C++, a reference) to a
           variable that goes out of scope after the function returns.

       -Wreturn-type
           Warn whenever a function is defined with a return type that defaults
           to "int".  Also warn about any "return" statement with no return
           value in a function whose return type is not "void" (falling off the
           end of the function body is considered returning without a value).

           For C only, warn about a "return" statement with an expression in a
           function whose return type is "void", unless the expression type is
           also "void".  As a GNU extension, the latter case is accepted without
           a warning unless -Wpedantic is used.  Attempting to use the return
           value of a non-"void" function other than "main" that flows off the
           end by reaching the closing curly brace that terminates the function
           is undefined.

           Unlike in C, in C++, flowing off the end of a non-"void" function
           other than "main" results in undefined behavior even when the value
           of the function is not used.

           This warning is enabled by default in C++ and by -Wall otherwise.

       -Wno-shift-count-negative
           Controls warnings if a shift count is negative.  This warning is
           enabled by default.

       -Wno-shift-count-overflow
           Controls warnings if a shift count is greater than or equal to the
           bit width of the type.  This warning is enabled by default.

       -Wshift-negative-value
           Warn if left shifting a negative value.  This warning is enabled by
           -Wextra in C99 and C++11 modes (and newer).

       -Wno-shift-overflow
       -Wshift-overflow=n
           These options control warnings about left shift overflows.

           -Wshift-overflow=1
               This is the warning level of -Wshift-overflow and is enabled by
               default in C99 and C++11 modes (and newer).  This warning level
               does not warn about left-shifting 1 into the sign bit.  (However,
               in C, such an overflow is still rejected in contexts where an
               integer constant expression is required.)  No warning is emitted
               in C++20 mode (and newer), as signed left shifts always wrap.

           -Wshift-overflow=2
               This warning level also warns about left-shifting 1 into the sign
               bit, unless C++14 mode (or newer) is active.

       -Wswitch
           Warn whenever a "switch" statement has an index of enumerated type
           and lacks a "case" for one or more of the named codes of that
           enumeration.  (The presence of a "default" label prevents this
           warning.)  "case" labels outside the enumeration range also provoke
           warnings when this option is used (even if there is a "default"
           label).  This warning is enabled by -Wall.

       -Wswitch-default
           Warn whenever a "switch" statement does not have a "default" case.

       -Wswitch-enum
           Warn whenever a "switch" statement has an index of enumerated type
           and lacks a "case" for one or more of the named codes of that
           enumeration.  "case" labels outside the enumeration range also
           provoke warnings when this option is used.  The only difference
           between -Wswitch and this option is that this option gives a warning
           about an omitted enumeration code even if there is a "default" label.

       -Wno-switch-bool
           Do not warn when a "switch" statement has an index of boolean type
           and the case values are outside the range of a boolean type.  It is
           possible to suppress this warning by casting the controlling
           expression to a type other than "bool".  For example:

                   switch ((int) (a == 4))
                     {
                     ...
                     }

           This warning is enabled by default for C and C++ programs.

       -Wno-switch-outside-range
           This option controls warnings when a "switch" case has a value that
           is outside of its respective type range.  This warning is enabled by
           default for C and C++ programs.

       -Wno-switch-unreachable
           Do not warn when a "switch" statement contains statements between the
           controlling expression and the first case label, which will never be
           executed.  For example:

                   switch (cond)
                     {
                      i = 15;
                     ...
                      case 5:
                     ...
                     }

           -Wswitch-unreachable does not warn if the statement between the
           controlling expression and the first case label is just a
           declaration:

                   switch (cond)
                     {
                      int i;
                     ...
                      case 5:
                      i = 5;
                     ...
                     }

           This warning is enabled by default for C and C++ programs.

       -Wsync-nand (C and C++ only)
           Warn when "__sync_fetch_and_nand" and "__sync_nand_and_fetch" built-
           in functions are used.  These functions changed semantics in GCC 4.4.

       -Wunused-but-set-parameter
           Warn whenever a function parameter is assigned to, but otherwise
           unused (aside from its declaration).

           To suppress this warning use the "unused" attribute.

           This warning is also enabled by -Wunused together with -Wextra.

       -Wunused-but-set-variable
           Warn whenever a local variable is assigned to, but otherwise unused
           (aside from its declaration).  This warning is enabled by -Wall.

           To suppress this warning use the "unused" attribute.

           This warning is also enabled by -Wunused, which is enabled by -Wall.

       -Wunused-function
           Warn whenever a static function is declared but not defined or a non-
           inline static function is unused.  This warning is enabled by -Wall.

       -Wunused-label
           Warn whenever a label is declared but not used.  This warning is
           enabled by -Wall.

           To suppress this warning use the "unused" attribute.

       -Wunused-local-typedefs (C, Objective-C, C++ and Objective-C++ only)
           Warn when a typedef locally defined in a function is not used.  This
           warning is enabled by -Wall.

       -Wunused-parameter
           Warn whenever a function parameter is unused aside from its
           declaration.

           To suppress this warning use the "unused" attribute.

       -Wno-unused-result
           Do not warn if a caller of a function marked with attribute
           "warn_unused_result" does not use its return value. The default is
           -Wunused-result.

       -Wunused-variable
           Warn whenever a local or static variable is unused aside from its
           declaration. This option implies -Wunused-const-variable=1 for C, but
           not for C++. This warning is enabled by -Wall.

           To suppress this warning use the "unused" attribute.

       -Wunused-const-variable
       -Wunused-const-variable=n
           Warn whenever a constant static variable is unused aside from its
           declaration.  -Wunused-const-variable=1 is enabled by
           -Wunused-variable for C, but not for C++. In C this declares variable
           storage, but in C++ this is not an error since const variables take
           the place of "#define"s.

           To suppress this warning use the "unused" attribute.

           -Wunused-const-variable=1
               This is the warning level that is enabled by -Wunused-variable
               for C.  It warns only about unused static const variables defined
               in the main compilation unit, but not about static const
               variables declared in any header included.

           -Wunused-const-variable=2
               This warning level also warns for unused constant static
               variables in headers (excluding system headers).  This is the
               warning level of -Wunused-const-variable and must be explicitly
               requested since in C++ this isn't an error and in C it might be
               harder to clean up all headers included.

       -Wunused-value
           Warn whenever a statement computes a result that is explicitly not
           used. To suppress this warning cast the unused expression to "void".
           This includes an expression-statement or the left-hand side of a
           comma expression that contains no side effects. For example, an
           expression such as "x[i,j]" causes a warning, while "x[(void)i,j]"
           does not.

           This warning is enabled by -Wall.

       -Wunused
           All the above -Wunused options combined.

           In order to get a warning about an unused function parameter, you
           must either specify -Wextra -Wunused (note that -Wall implies
           -Wunused), or separately specify -Wunused-parameter.

       -Wuninitialized
           Warn if an object with automatic or allocated storage duration is
           used without having been initialized.  In C++, also warn if a non-
           static reference or non-static "const" member appears in a class
           without constructors.

           In addition, passing a pointer (or in C++, a reference) to an
           uninitialized object to a "const"-qualified argument of a built-in
           function known to read the object is also diagnosed by this warning.
           (-Wmaybe-uninitialized is issued for ordinary functions.)

           If you want to warn about code that uses the uninitialized value of
           the variable in its own initializer, use the -Winit-self option.

           These warnings occur for individual uninitialized elements of
           structure, union or array variables as well as for variables that are
           uninitialized as a whole.  They do not occur for variables or
           elements declared "volatile".  Because these warnings depend on
           optimization, the exact variables or elements for which there are
           warnings depend on the precise optimization options and version of
           GCC used.

           Note that there may be no warning about a variable that is used only
           to compute a value that itself is never used, because such
           computations may be deleted by data flow analysis before the warnings
           are printed.

       -Wno-invalid-memory-model
           This option controls warnings for invocations of __atomic Builtins,
           __sync Builtins, and the C11 atomic generic functions with a memory
           consistency argument that is either invalid for the operation or
           outside the range of values of the "memory_order" enumeration.  For
           example, since the "__atomic_store" and "__atomic_store_n" built-ins
           are only defined for the relaxed, release, and sequentially
           consistent memory orders the following code is diagnosed:

                   void store (int *i)
                   {
                     __atomic_store_n (i, 0, memory_order_consume);
                   }

           -Winvalid-memory-model is enabled by default.

       -Wmaybe-uninitialized
           For an object with automatic or allocated storage duration, if there
           exists a path from the function entry to a use of the object that is
           initialized, but there exist some other paths for which the object is
           not initialized, the compiler emits a warning if it cannot prove the
           uninitialized paths are not executed at run time.

           In addition, passing a pointer (or in C++, a reference) to an
           uninitialized object to a "const"-qualified function argument is also
           diagnosed by this warning.  (-Wuninitialized is issued for built-in
           functions known to read the object.)  Annotating the function with
           attribute "access (none)" indicates that the argument isn't used to
           access the object and avoids the warning.

           These warnings are only possible in optimizing compilation, because
           otherwise GCC does not keep track of the state of variables.

           These warnings are made optional because GCC may not be able to
           determine when the code is correct in spite of appearing to have an
           error.  Here is one example of how this can happen:

                   {
                     int x;
                     switch (y)
                       {
                       case 1: x = 1;
                         break;
                       case 2: x = 4;
                         break;
                       case 3: x = 5;
                       }
                     foo (x);
                   }

           If the value of "y" is always 1, 2 or 3, then "x" is always
           initialized, but GCC doesn't know this. To suppress the warning, you
           need to provide a default case with assert(0) or similar code.

           This option also warns when a non-volatile automatic variable might
           be changed by a call to "longjmp".  The compiler sees only the calls
           to "setjmp".  It cannot know where "longjmp" will be called; in fact,
           a signal handler could call it at any point in the code.  As a
           result, you may get a warning even when there is in fact no problem
           because "longjmp" cannot in fact be called at the place that would
           cause a problem.

           Some spurious warnings can be avoided if you declare all the
           functions you use that never return as "noreturn".

           This warning is enabled by -Wall or -Wextra.

       -Wunknown-pragmas
           Warn when a "#pragma" directive is encountered that is not understood
           by GCC.  If this command-line option is used, warnings are even
           issued for unknown pragmas in system header files.  This is not the
           case if the warnings are only enabled by the -Wall command-line
           option.

       -Wno-pragmas
           Do not warn about misuses of pragmas, such as incorrect parameters,
           invalid syntax, or conflicts between pragmas.  See also
           -Wunknown-pragmas.

       -Wno-prio-ctor-dtor
           Do not warn if a priority from 0 to 100 is used for constructor or
           destructor.  The use of constructor and destructor attributes allow
           you to assign a priority to the constructor/destructor to control its
           order of execution before "main" is called or after it returns.  The
           priority values must be greater than 100 as the compiler reserves
           priority values between 0--100 for the implementation.

       -Wstrict-aliasing
           This option is only active when -fstrict-aliasing is active.  It
           warns about code that might break the strict aliasing rules that the
           compiler is using for optimization.  The warning does not catch all
           cases, but does attempt to catch the more common pitfalls.  It is
           included in -Wall.  It is equivalent to -Wstrict-aliasing=3

       -Wstrict-aliasing=n
           This option is only active when -fstrict-aliasing is active.  It
           warns about code that might break the strict aliasing rules that the
           compiler is using for optimization.  Higher levels correspond to
           higher accuracy (fewer false positives).  Higher levels also
           correspond to more effort, similar to the way -O works.
           -Wstrict-aliasing is equivalent to -Wstrict-aliasing=3.

           Level 1: Most aggressive, quick, least accurate.  Possibly useful
           when higher levels do not warn but -fstrict-aliasing still breaks the
           code, as it has very few false negatives.  However, it has many false
           positives.  Warns for all pointer conversions between possibly
           incompatible types, even if never dereferenced.  Runs in the front
           end only.

           Level 2: Aggressive, quick, not too precise.  May still have many
           false positives (not as many as level 1 though), and few false
           negatives (but possibly more than level 1).  Unlike level 1, it only
           warns when an address is taken.  Warns about incomplete types.  Runs
           in the front end only.

           Level 3 (default for -Wstrict-aliasing): Should have very few false
           positives and few false negatives.  Slightly slower than levels 1 or
           2 when optimization is enabled.  Takes care of the common
           pun+dereference pattern in the front end: "*(int*)&some_float".  If
           optimization is enabled, it also runs in the back end, where it deals
           with multiple statement cases using flow-sensitive points-to
           information.  Only warns when the converted pointer is dereferenced.
           Does not warn about incomplete types.

       -Wstrict-overflow
       -Wstrict-overflow=n
           This option is only active when signed overflow is undefined.  It
           warns about cases where the compiler optimizes based on the
           assumption that signed overflow does not occur.  Note that it does
           not warn about all cases where the code might overflow: it only warns
           about cases where the compiler implements some optimization.  Thus
           this warning depends on the optimization level.

           An optimization that assumes that signed overflow does not occur is
           perfectly safe if the values of the variables involved are such that
           overflow never does, in fact, occur.  Therefore this warning can
           easily give a false positive: a warning about code that is not
           actually a problem.  To help focus on important issues, several
           warning levels are defined.  No warnings are issued for the use of
           undefined signed overflow when estimating how many iterations a loop
           requires, in particular when determining whether a loop will be
           executed at all.

           -Wstrict-overflow=1
               Warn about cases that are both questionable and easy to avoid.
               For example the compiler simplifies "x + 1 > x" to 1.  This level
               of -Wstrict-overflow is enabled by -Wall; higher levels are not,
               and must be explicitly requested.

           -Wstrict-overflow=2
               Also warn about other cases where a comparison is simplified to a
               constant.  For example: "abs (x) >= 0".  This can only be
               simplified when signed integer overflow is undefined, because
               "abs (INT_MIN)" overflows to "INT_MIN", which is less than zero.
               -Wstrict-overflow (with no level) is the same as
               -Wstrict-overflow=2.

           -Wstrict-overflow=3
               Also warn about other cases where a comparison is simplified.
               For example: "x + 1 > 1" is simplified to "x > 0".

           -Wstrict-overflow=4
               Also warn about other simplifications not covered by the above
               cases.  For example: "(x * 10) / 5" is simplified to "x * 2".

           -Wstrict-overflow=5
               Also warn about cases where the compiler reduces the magnitude of
               a constant involved in a comparison.  For example: "x + 2 > y" is
               simplified to "x + 1 >= y".  This is reported only at the highest
               warning level because this simplification applies to many
               comparisons, so this warning level gives a very large number of
               false positives.

       -Wstring-compare
           Warn for calls to "strcmp" and "strncmp" whose result is determined
           to be either zero or non-zero in tests for such equality owing to the
           length of one argument being greater than the size of the array the
           other argument is stored in (or the bound in the case of "strncmp").
           Such calls could be mistakes.  For example, the call to "strcmp"
           below is diagnosed because its result is necessarily non-zero
           irrespective of the contents of the array "a".

                   extern char a[4];
                   void f (char *d)
                   {
                     strcpy (d, "string");
                     ...
                     if (0 == strcmp (a, d))   // cannot be true
                       puts ("a and d are the same");
                   }

           -Wstring-compare is enabled by -Wextra.

       -Wno-stringop-overflow
       -Wstringop-overflow
       -Wstringop-overflow=type
           Warn for calls to string manipulation functions such as "memcpy" and
           "strcpy" that are determined to overflow the destination buffer.  The
           optional argument is one greater than the type of Object Size
           Checking to perform to determine the size of the destination.  The
           argument is meaningful only for functions that operate on character
           arrays but not for raw memory functions like "memcpy" which always
           make use of Object Size type-0.  The option also warns for calls that
           specify a size in excess of the largest possible object or at most
           "SIZE_MAX / 2" bytes.  The option produces the best results with
           optimization enabled but can detect a small subset of simple buffer
           overflows even without optimization in calls to the GCC built-in
           functions like "__builtin_memcpy" that correspond to the standard
           functions.  In any case, the option warns about just a subset of
           buffer overflows detected by the corresponding overflow checking
           built-ins.  For example, the option issues a warning for the "strcpy"
           call below because it copies at least 5 characters (the string "blue"
           including the terminating NUL) into the buffer of size 4.

                   enum Color { blue, purple, yellow };
                   const char* f (enum Color clr)
                   {
                     static char buf [4];
                     const char *str;
                     switch (clr)
                       {
                         case blue: str = "blue"; break;
                         case purple: str = "purple"; break;
                         case yellow: str = "yellow"; break;
                       }

                     return strcpy (buf, str);   // warning here
                   }

           Option -Wstringop-overflow=2 is enabled by default.

           -Wstringop-overflow
           -Wstringop-overflow=1
               The -Wstringop-overflow=1 option uses type-zero Object Size
               Checking to determine the sizes of destination objects.  At this
               setting the option does not warn for writes past the end of
               subobjects of larger objects accessed by pointers unless the size
               of the largest surrounding object is known.  When the destination
               may be one of several objects it is assumed to be the largest one
               of them.  On Linux systems, when optimization is enabled at this
               setting the option warns for the same code as when the
               "_FORTIFY_SOURCE" macro is defined to a non-zero value.

           -Wstringop-overflow=2
               The -Wstringop-overflow=2 option uses type-one Object Size
               Checking to determine the sizes of destination objects.  At this
               setting the option warns about overflows when writing to members
               of the largest complete objects whose exact size is known.
               However, it does not warn for excessive writes to the same
               members of unknown objects referenced by pointers since they may
               point to arrays containing unknown numbers of elements.  This is
               the default setting of the option.

           -Wstringop-overflow=3
               The -Wstringop-overflow=3 option uses type-two Object Size
               Checking to determine the sizes of destination objects.  At this
               setting the option warns about overflowing the smallest object or
               data member.  This is the most restrictive setting of the option
               that may result in warnings for safe code.

           -Wstringop-overflow=4
               The -Wstringop-overflow=4 option uses type-three Object Size
               Checking to determine the sizes of destination objects.  At this
               setting the option warns about overflowing any data members, and
               when the destination is one of several objects it uses the size
               of the largest of them to decide whether to issue a warning.
               Similarly to -Wstringop-overflow=3 this setting of the option may
               result in warnings for benign code.

       -Wno-stringop-overread
           Warn for calls to string manipulation functions such as "memchr", or
           "strcpy" that are determined to read past the end of the source
           sequence.

           Option -Wstringop-overread is enabled by default.

       -Wno-stringop-truncation
           Do not warn for calls to bounded string manipulation functions such
           as "strncat", "strncpy", and "stpncpy" that may either truncate the
           copied string or leave the destination unchanged.

           In the following example, the call to "strncat" specifies a bound
           that is less than the length of the source string.  As a result, the
           copy of the source will be truncated and so the call is diagnosed.
           To avoid the warning use "bufsize - strlen (buf) - 1)" as the bound.

                   void append (char *buf, size_t bufsize)
                   {
                     strncat (buf, ".txt", 3);
                   }

           As another example, the following call to "strncpy" results in
           copying to "d" just the characters preceding the terminating NUL,
           without appending the NUL to the end.  Assuming the result of
           "strncpy" is necessarily a NUL-terminated string is a common mistake,
           and so the call is diagnosed.  To avoid the warning when the result
           is not expected to be NUL-terminated, call "memcpy" instead.

                   void copy (char *d, const char *s)
                   {
                     strncpy (d, s, strlen (s));
                   }

           In the following example, the call to "strncpy" specifies the size of
           the destination buffer as the bound.  If the length of the source
           string is equal to or greater than this size the result of the copy
           will not be NUL-terminated.  Therefore, the call is also diagnosed.
           To avoid the warning, specify "sizeof buf - 1" as the bound and set
           the last element of the buffer to "NUL".

                   void copy (const char *s)
                   {
                     char buf[80];
                     strncpy (buf, s, sizeof buf);
                     ...
                   }

           In situations where a character array is intended to store a sequence
           of bytes with no terminating "NUL" such an array may be annotated
           with attribute "nonstring" to avoid this warning.  Such arrays,
           however, are not suitable arguments to functions that expect
           "NUL"-terminated strings.  To help detect accidental misuses of such
           arrays GCC issues warnings unless it can prove that the use is safe.

       -Wsuggest-attribute=[pure|const|noreturn|format|cold|malloc]
           Warn for cases where adding an attribute may be beneficial. The
           attributes currently supported are listed below.

           -Wsuggest-attribute=pure
           -Wsuggest-attribute=const
           -Wsuggest-attribute=noreturn
           -Wmissing-noreturn
           -Wsuggest-attribute=malloc
               Warn about functions that might be candidates for attributes
               "pure", "const" or "noreturn" or "malloc". The compiler only
               warns for functions visible in other compilation units or (in the
               case of "pure" and "const") if it cannot prove that the function
               returns normally. A function returns normally if it doesn't
               contain an infinite loop or return abnormally by throwing,
               calling "abort" or trapping.  This analysis requires option
               -fipa-pure-const, which is enabled by default at -O and higher.
               Higher optimization levels improve the accuracy of the analysis.

           -Wsuggest-attribute=format
           -Wmissing-format-attribute
               Warn about function pointers that might be candidates for
               "format" attributes.  Note these are only possible candidates,
               not absolute ones.  GCC guesses that function pointers with
               "format" attributes that are used in assignment, initialization,
               parameter passing or return statements should have a
               corresponding "format" attribute in the resulting type.  I.e. the
               left-hand side of the assignment or initialization, the type of
               the parameter variable, or the return type of the containing
               function respectively should also have a "format" attribute to
               avoid the warning.

               GCC also warns about function definitions that might be
               candidates for "format" attributes.  Again, these are only
               possible candidates.  GCC guesses that "format" attributes might
               be appropriate for any function that calls a function like
               "vprintf" or "vscanf", but this might not always be the case, and
               some functions for which "format" attributes are appropriate may
               not be detected.

           -Wsuggest-attribute=cold
               Warn about functions that might be candidates for "cold"
               attribute.  This is based on static detection and generally only
               warns about functions which always leads to a call to another
               "cold" function such as wrappers of C++ "throw" or fatal error
               reporting functions leading to "abort".

       -Walloc-zero
           Warn about calls to allocation functions decorated with attribute
           "alloc_size" that specify zero bytes, including those to the built-in
           forms of the functions "aligned_alloc", "alloca", "calloc", "malloc",
           and "realloc".  Because the behavior of these functions when called
           with a zero size differs among implementations (and in the case of
           "realloc" has been deprecated) relying on it may result in subtle
           portability bugs and should be avoided.

       -Walloc-size-larger-than=byte-size
           Warn about calls to functions decorated with attribute "alloc_size"
           that attempt to allocate objects larger than the specified number of
           bytes, or where the result of the size computation in an integer type
           with infinite precision would exceed the value of PTRDIFF_MAX on the
           target.  -Walloc-size-larger-than=PTRDIFF_MAX is enabled by default.
           Warnings controlled by the option can be disabled either by
           specifying byte-size of SIZE_MAX or more or by
           -Wno-alloc-size-larger-than.

       -Wno-alloc-size-larger-than
           Disable -Walloc-size-larger-than= warnings.  The option is equivalent
           to -Walloc-size-larger-than=SIZE_MAX or larger.

       -Walloca
           This option warns on all uses of "alloca" in the source.

       -Walloca-larger-than=byte-size
           This option warns on calls to "alloca" with an integer argument whose
           value is either zero, or that is not bounded by a controlling
           predicate that limits its value to at most byte-size.  It also warns
           for calls to "alloca" where the bound value is unknown.  Arguments of
           non-integer types are considered unbounded even if they appear to be
           constrained to the expected range.

           For example, a bounded case of "alloca" could be:

                   void func (size_t n)
                   {
                     void *p;
                     if (n <= 1000)
                       p = alloca (n);
                     else
                       p = malloc (n);
                     f (p);
                   }

           In the above example, passing "-Walloca-larger-than=1000" would not
           issue a warning because the call to "alloca" is known to be at most
           1000 bytes.  However, if "-Walloca-larger-than=500" were passed, the
           compiler would emit a warning.

           Unbounded uses, on the other hand, are uses of "alloca" with no
           controlling predicate constraining its integer argument.  For
           example:

                   void func ()
                   {
                     void *p = alloca (n);
                     f (p);
                   }

           If "-Walloca-larger-than=500" were passed, the above would trigger a
           warning, but this time because of the lack of bounds checking.

           Note, that even seemingly correct code involving signed integers
           could cause a warning:

                   void func (signed int n)
                   {
                     if (n < 500)
                       {
                         p = alloca (n);
                         f (p);
                       }
                   }

           In the above example, n could be negative, causing a larger than
           expected argument to be implicitly cast into the "alloca" call.

           This option also warns when "alloca" is used in a loop.

           -Walloca-larger-than=PTRDIFF_MAX is enabled by default but is usually
           only effective  when -ftree-vrp is active (default for -O2 and
           above).

           See also -Wvla-larger-than=byte-size.

       -Wno-alloca-larger-than
           Disable -Walloca-larger-than= warnings.  The option is equivalent to
           -Walloca-larger-than=SIZE_MAX or larger.

       -Warith-conversion
           Do warn about implicit conversions from arithmetic operations even
           when conversion of the operands to the same type cannot change their
           values.  This affects warnings from -Wconversion, -Wfloat-conversion,
           and -Wsign-conversion.

                   void f (char c, int i)
                   {
                     c = c + i; // warns with B<-Wconversion>
                     c = c + 1; // only warns with B<-Warith-conversion>
                   }

       -Warray-bounds
       -Warray-bounds=n
           This option is only active when -ftree-vrp is active (default for -O2
           and above). It warns about subscripts to arrays that are always out
           of bounds. This warning is enabled by -Wall.

           -Warray-bounds=1
               This is the warning level of -Warray-bounds and is enabled by
               -Wall; higher levels are not, and must be explicitly requested.

           -Warray-bounds=2
               This warning level also warns about out of bounds access for
               arrays at the end of a struct and for arrays accessed through
               pointers. This warning level may give a larger number of false
               positives and is deactivated by default.

       -Warray-parameter
       -Warray-parameter=n
           Warn about redeclarations of functions involving arguments of array
           or pointer types of inconsistent kinds or forms, and enable the
           detection of out-of-bounds accesses to such parameters by warnings
           such as -Warray-bounds.

           If the first function declaration uses the array form the bound
           specified in the array is assumed to be the minimum number of
           elements expected to be provided in calls to the function and the
           maximum number of elements accessed by it.  Failing to provide
           arguments of sufficient size or accessing more than the maximum
           number of elements may be diagnosed by warnings such as
           -Warray-bounds.  At level 1 the warning diagnoses inconsistencies
           involving array parameters declared using the "T[static N]" form.

           For example, the warning triggers for the following redeclarations
           because the first one allows an array of any size to be passed to "f"
           while the second one with the keyword "static" specifies that the
           array argument must have at least four elements.

                   void f (int[static 4]);
                   void f (int[]);           // warning (inconsistent array form)

                   void g (void)
                   {
                     int *p = (int *)malloc (4);
                     f (p);                  // warning (array too small)
                     ...
                   }

           At level 2 the warning also triggers for redeclarations involving any
           other inconsistency in array or pointer argument forms denoting array
           sizes.  Pointers and arrays of unspecified bound are considered
           equivalent and do not trigger a warning.

                   void g (int*);
                   void g (int[]);     // no warning
                   void g (int[8]);    // warning (inconsistent array bound)

           -Warray-parameter=2 is included in -Wall.  The -Wvla-parameter option
           triggers warnings for similar inconsistencies involving Variable
           Length Array arguments.

       -Wattribute-alias=n
       -Wno-attribute-alias
           Warn about declarations using the "alias" and similar attributes
           whose target is incompatible with the type of the alias.

           -Wattribute-alias=1
               The default warning level of the -Wattribute-alias option
               diagnoses incompatibilities between the type of the alias
               declaration and that of its target.  Such incompatibilities are
               typically indicative of bugs.

           -Wattribute-alias=2
               At this level -Wattribute-alias also diagnoses cases where the
               attributes of the alias declaration are more restrictive than the
               attributes applied to its target.  These mismatches can
               potentially result in incorrect code generation.  In other cases
               they may be benign and could be resolved simply by adding the
               missing attribute to the target.  For comparison, see the
               -Wmissing-attributes option, which controls diagnostics when the
               alias declaration is less restrictive than the target, rather
               than more restrictive.

               Attributes considered include "alloc_align", "alloc_size",
               "cold", "const", "hot", "leaf", "malloc", "nonnull", "noreturn",
               "nothrow", "pure", "returns_nonnull", and "returns_twice".

           -Wattribute-alias is equivalent to -Wattribute-alias=1.  This is the
           default.  You can disable these warnings with either
           -Wno-attribute-alias or -Wattribute-alias=0.

       -Wbool-compare
           Warn about boolean expression compared with an integer value
           different from "true"/"false".  For instance, the following
           comparison is always false:

                   int n = 5;
                   ...
                   if ((n > 1) == 2) { ... }

           This warning is enabled by -Wall.

       -Wbool-operation
           Warn about suspicious operations on expressions of a boolean type.
           For instance, bitwise negation of a boolean is very likely a bug in
           the program.  For C, this warning also warns about incrementing or
           decrementing a boolean, which rarely makes sense.  (In C++,
           decrementing a boolean is always invalid.  Incrementing a boolean is
           invalid in C++17, and deprecated otherwise.)

           This warning is enabled by -Wall.

       -Wduplicated-branches
           Warn when an if-else has identical branches.  This warning detects
           cases like

                   if (p != NULL)
                     return 0;
                   else
                     return 0;

           It doesn't warn when both branches contain just a null statement.
           This warning also warn for conditional operators:

                     int i = x ? *p : *p;

       -Wduplicated-cond
           Warn about duplicated conditions in an if-else-if chain.  For
           instance, warn for the following code:

                   if (p->q != NULL) { ... }
                   else if (p->q != NULL) { ... }

       -Wframe-address
           Warn when the __builtin_frame_address or __builtin_return_address is
           called with an argument greater than 0.  Such calls may return
           indeterminate values or crash the program.  The warning is included
           in -Wall.

       -Wno-discarded-qualifiers (C and Objective-C only)
           Do not warn if type qualifiers on pointers are being discarded.
           Typically, the compiler warns if a "const char *" variable is passed
           to a function that takes a "char *" parameter.  This option can be
           used to suppress such a warning.

       -Wno-discarded-array-qualifiers (C and Objective-C only)
           Do not warn if type qualifiers on arrays which are pointer targets
           are being discarded.  Typically, the compiler warns if a "const int
           (*)[]" variable is passed to a function that takes a "int (*)[]"
           parameter.  This option can be used to suppress such a warning.

       -Wno-incompatible-pointer-types (C and Objective-C only)
           Do not warn when there is a conversion between pointers that have
           incompatible types.  This warning is for cases not covered by
           -Wno-pointer-sign, which warns for pointer argument passing or
           assignment with different signedness.

       -Wno-int-conversion (C and Objective-C only)
           Do not warn about incompatible integer to pointer and pointer to
           integer conversions.  This warning is about implicit conversions; for
           explicit conversions the warnings -Wno-int-to-pointer-cast and
           -Wno-pointer-to-int-cast may be used.

       -Wzero-length-bounds
           Warn about accesses to elements of zero-length array members that
           might overlap other members of the same object.  Declaring interior
           zero-length arrays is discouraged because accesses to them are
           undefined.  See

           For example, the first two stores in function "bad" are diagnosed
           because the array elements overlap the subsequent members "b" and
           "c".  The third store is diagnosed by -Warray-bounds because it is
           beyond the bounds of the enclosing object.

                   struct X { int a[0]; int b, c; };
                   struct X x;

                   void bad (void)
                   {
                     x.a[0] = 0;   // -Wzero-length-bounds
                     x.a[1] = 1;   // -Wzero-length-bounds
                     x.a[2] = 2;   // -Warray-bounds
                   }

           Option -Wzero-length-bounds is enabled by -Warray-bounds.

       -Wno-div-by-zero
           Do not warn about compile-time integer division by zero.  Floating-
           point division by zero is not warned about, as it can be a legitimate
           way of obtaining infinities and NaNs.

       -Wsystem-headers
           Print warning messages for constructs found in system header files.
           Warnings from system headers are normally suppressed, on the
           assumption that they usually do not indicate real problems and would
           only make the compiler output harder to read.  Using this command-
           line option tells GCC to emit warnings from system headers as if they
           occurred in user code.  However, note that using -Wall in conjunction
           with this option does not warn about unknown pragmas in system
           headers---for that, -Wunknown-pragmas must also be used.

       -Wtautological-compare
           Warn if a self-comparison always evaluates to true or false.  This
           warning detects various mistakes such as:

                   int i = 1;
                   ...
                   if (i > i) { ... }

           This warning also warns about bitwise comparisons that always
           evaluate to true or false, for instance:

                   if ((a & 16) == 10) { ... }

           will always be false.

           This warning is enabled by -Wall.

       -Wtrampolines
           Warn about trampolines generated for pointers to nested functions.  A
           trampoline is a small piece of data or code that is created at run
           time on the stack when the address of a nested function is taken, and
           is used to call the nested function indirectly.  For some targets, it
           is made up of data only and thus requires no special treatment.  But,
           for most targets, it is made up of code and thus requires the stack
           to be made executable in order for the program to work properly.

       -Wfloat-equal
           Warn if floating-point values are used in equality comparisons.

           The idea behind this is that sometimes it is convenient (for the
           programmer) to consider floating-point values as approximations to
           infinitely precise real numbers.  If you are doing this, then you
           need to compute (by analyzing the code, or in some other way) the
           maximum or likely maximum error that the computation introduces, and
           allow for it when performing comparisons (and when producing output,
           but that's a different problem).  In particular, instead of testing
           for equality, you should check to see whether the two values have
           ranges that overlap; and this is done with the relational operators,
           so equality comparisons are probably mistaken.

       -Wtraditional (C and Objective-C only)
           Warn about certain constructs that behave differently in traditional
           and ISO C.  Also warn about ISO C constructs that have no traditional
           C equivalent, and/or problematic constructs that should be avoided.

           *   Macro parameters that appear within string literals in the macro
               body.  In traditional C macro replacement takes place within
               string literals, but in ISO C it does not.

           *   In traditional C, some preprocessor directives did not exist.
               Traditional preprocessors only considered a line to be a
               directive if the # appeared in column 1 on the line.  Therefore
               -Wtraditional warns about directives that traditional C
               understands but ignores because the # does not appear as the
               first character on the line.  It also suggests you hide
               directives like "#pragma" not understood by traditional C by
               indenting them.  Some traditional implementations do not
               recognize "#elif", so this option suggests avoiding it
               altogether.

           *   A function-like macro that appears without arguments.

           *   The unary plus operator.

           *   The U integer constant suffix, or the F or L floating-point
               constant suffixes.  (Traditional C does support the L suffix on
               integer constants.)  Note, these suffixes appear in macros
               defined in the system headers of most modern systems, e.g. the
               _MIN/_MAX macros in "<limits.h>".  Use of these macros in user
               code might normally lead to spurious warnings, however GCC's
               integrated preprocessor has enough context to avoid warning in
               these cases.

           *   A function declared external in one block and then used after the
               end of the block.

           *   A "switch" statement has an operand of type "long".

           *   A non-"static" function declaration follows a "static" one.  This
               construct is not accepted by some traditional C compilers.

           *   The ISO type of an integer constant has a different width or
               signedness from its traditional type.  This warning is only
               issued if the base of the constant is ten.  I.e. hexadecimal or
               octal values, which typically represent bit patterns, are not
               warned about.

           *   Usage of ISO string concatenation is detected.

           *   Initialization of automatic aggregates.

           *   Identifier conflicts with labels.  Traditional C lacks a separate
               namespace for labels.

           *   Initialization of unions.  If the initializer is zero, the
               warning is omitted.  This is done under the assumption that the
               zero initializer in user code appears conditioned on e.g.
               "__STDC__" to avoid missing initializer warnings and relies on
               default initialization to zero in the traditional C case.

           *   Conversions by prototypes between fixed/floating-point values and
               vice versa.  The absence of these prototypes when compiling with
               traditional C causes serious problems.  This is a subset of the
               possible conversion warnings; for the full set use
               -Wtraditional-conversion.

           *   Use of ISO C style function definitions.  This warning
               intentionally is not issued for prototype declarations or
               variadic functions because these ISO C features appear in your
               code when using libiberty's traditional C compatibility macros,
               "PARAMS" and "VPARAMS".  This warning is also bypassed for nested
               functions because that feature is already a GCC extension and
               thus not relevant to traditional C compatibility.

       -Wtraditional-conversion (C and Objective-C only)
           Warn if a prototype causes a type conversion that is different from
           what would happen to the same argument in the absence of a prototype.
           This includes conversions of fixed point to floating and vice versa,
           and conversions changing the width or signedness of a fixed-point
           argument except when the same as the default promotion.

       -Wdeclaration-after-statement (C and Objective-C only)
           Warn when a declaration is found after a statement in a block.  This
           construct, known from C++, was introduced with ISO C99 and is by
           default allowed in GCC.  It is not supported by ISO C90.

       -Wshadow
           Warn whenever a local variable or type declaration shadows another
           variable, parameter, type, class member (in C++), or instance
           variable (in Objective-C) or whenever a built-in function is
           shadowed.  Note that in C++, the compiler warns if a local variable
           shadows an explicit typedef, but not if it shadows a
           struct/class/enum.  If this warning is enabled, it includes also all
           instances of local shadowing.  This means that -Wno-shadow=local and
           -Wno-shadow=compatible-local are ignored when -Wshadow is used.  Same
           as -Wshadow=global.

       -Wno-shadow-ivar (Objective-C only)
           Do not warn whenever a local variable shadows an instance variable in
           an Objective-C method.

       -Wshadow=global
           Warn for any shadowing.  Same as -Wshadow.

       -Wshadow=local
           Warn when a local variable shadows another local variable or
           parameter.

       -Wshadow=compatible-local
           Warn when a local variable shadows another local variable or
           parameter whose type is compatible with that of the shadowing
           variable.  In C++, type compatibility here means the type of the
           shadowing variable can be converted to that of the shadowed variable.
           The creation of this flag (in addition to -Wshadow=local) is based on
           the idea that when a local variable shadows another one of
           incompatible type, it is most likely intentional, not a bug or typo,
           as shown in the following example:

                   for (SomeIterator i = SomeObj.begin(); i != SomeObj.end(); ++i)
                   {
                     for (int i = 0; i < N; ++i)
                     {
                       ...
                     }
                     ...
                   }

           Since the two variable "i" in the example above have incompatible
           types, enabling only -Wshadow=compatible-local does not emit a
           warning.  Because their types are incompatible, if a programmer
           accidentally uses one in place of the other, type checking is
           expected to catch that and emit an error or warning.  Use of this
           flag instead of -Wshadow=local can possibly reduce the number of
           warnings triggered by intentional shadowing.  Note that this also
           means that shadowing "const char *i" by "char *i" does not emit a
           warning.

           This warning is also enabled by -Wshadow=local.

       -Wlarger-than=byte-size
           Warn whenever an object is defined whose size exceeds byte-size.
           -Wlarger-than=PTRDIFF_MAX is enabled by default.  Warnings controlled
           by the option can be disabled either by specifying byte-size of
           SIZE_MAX or more or by -Wno-larger-than.

           Also warn for calls to bounded functions such as "memchr" or
           "strnlen" that specify a bound greater than the largest possible
           object, which is PTRDIFF_MAX bytes by default.  These warnings can
           only be disabled by -Wno-larger-than.

       -Wno-larger-than
           Disable -Wlarger-than= warnings.  The option is equivalent to
           -Wlarger-than=SIZE_MAX or larger.

       -Wframe-larger-than=byte-size
           Warn if the size of a function frame exceeds byte-size.  The
           computation done to determine the stack frame size is approximate and
           not conservative.  The actual requirements may be somewhat greater
           than byte-size even if you do not get a warning.  In addition, any
           space allocated via "alloca", variable-length arrays, or related
           constructs is not included by the compiler when determining whether
           or not to issue a warning.  -Wframe-larger-than=PTRDIFF_MAX is
           enabled by default.  Warnings controlled by the option can be
           disabled either by specifying byte-size of SIZE_MAX or more or by
           -Wno-frame-larger-than.

       -Wno-frame-larger-than
           Disable -Wframe-larger-than= warnings.  The option is equivalent to
           -Wframe-larger-than=SIZE_MAX or larger.

       -Wno-free-nonheap-object
           Warn when attempting to deallocate an object that was either not
           allocated on the heap, or by using a pointer that was not returned
           from a prior call to the corresponding allocation function.  For
           example, because the call to "stpcpy" returns a pointer to the
           terminating nul character and not to the begginning of the object,
           the call to "free" below is diagnosed.

                   void f (char *p)
                   {
                     p = stpcpy (p, "abc");
                     // ...
                     free (p);   // warning
                   }

           -Wfree-nonheap-object is enabled by default.

       -Wstack-usage=byte-size
           Warn if the stack usage of a function might exceed byte-size.  The
           computation done to determine the stack usage is conservative.  Any
           space allocated via "alloca", variable-length arrays, or related
           constructs is included by the compiler when determining whether or
           not to issue a warning.

           The message is in keeping with the output of -fstack-usage.

           *   If the stack usage is fully static but exceeds the specified
               amount, it's:

                         warning: stack usage is 1120 bytes

           *   If the stack usage is (partly) dynamic but bounded, it's:

                         warning: stack usage might be 1648 bytes

           *   If the stack usage is (partly) dynamic and not bounded, it's:

                         warning: stack usage might be unbounded

           -Wstack-usage=PTRDIFF_MAX is enabled by default.  Warnings controlled
           by the option can be disabled either by specifying byte-size of
           SIZE_MAX or more or by -Wno-stack-usage.

       -Wno-stack-usage
           Disable -Wstack-usage= warnings.  The option is equivalent to
           -Wstack-usage=SIZE_MAX or larger.

       -Wunsafe-loop-optimizations
           Warn if the loop cannot be optimized because the compiler cannot
           assume anything on the bounds of the loop indices.  With
           -funsafe-loop-optimizations warn if the compiler makes such
           assumptions.

       -Wno-pedantic-ms-format (MinGW targets only)
           When used in combination with -Wformat and -pedantic without GNU
           extensions, this option disables the warnings about non-ISO "printf"
           / "scanf" format width specifiers "I32", "I64", and "I" used on
           Windows targets, which depend on the MS runtime.

       -Wpointer-arith
           Warn about anything that depends on the "size of" a function type or
           of "void".  GNU C assigns these types a size of 1, for convenience in
           calculations with "void *" pointers and pointers to functions.  In
           C++, warn also when an arithmetic operation involves "NULL".  This
           warning is also enabled by -Wpedantic.

       -Wno-pointer-compare
           Do not warn if a pointer is compared with a zero character constant.
           This usually means that the pointer was meant to be dereferenced.
           For example:

                   const char *p = foo ();
                   if (p == '\0')
                     return 42;

           Note that the code above is invalid in C++11.

           This warning is enabled by default.

       -Wtsan
           Warn about unsupported features in ThreadSanitizer.

           ThreadSanitizer does not support "std::atomic_thread_fence" and can
           report false positives.

           This warning is enabled by default.

       -Wtype-limits
           Warn if a comparison is always true or always false due to the
           limited range of the data type, but do not warn for constant
           expressions.  For example, warn if an unsigned variable is compared
           against zero with "<" or ">=".  This warning is also enabled by
           -Wextra.

       -Wabsolute-value (C and Objective-C only)
           Warn for calls to standard functions that compute the absolute value
           of an argument when a more appropriate standard function is
           available.  For example, calling "abs(3.14)" triggers the warning
           because the appropriate function to call to compute the absolute
           value of a double argument is "fabs".  The option also triggers
           warnings when the argument in a call to such a function has an
           unsigned type.  This warning can be suppressed with an explicit type
           cast and it is also enabled by -Wextra.

       -Wcomment
       -Wcomments
           Warn whenever a comment-start sequence /* appears in a /* comment, or
           whenever a backslash-newline appears in a // comment.  This warning
           is enabled by -Wall.

       -Wtrigraphs
           Warn if any trigraphs are encountered that might change the meaning
           of the program.  Trigraphs within comments are not warned about,
           except those that would form escaped newlines.

           This option is implied by -Wall.  If -Wall is not given, this option
           is still enabled unless trigraphs are enabled.  To get trigraph
           conversion without warnings, but get the other -Wall warnings, use
           -trigraphs -Wall -Wno-trigraphs.

       -Wundef
           Warn if an undefined identifier is evaluated in an "#if" directive.
           Such identifiers are replaced with zero.

       -Wexpansion-to-defined
           Warn whenever defined is encountered in the expansion of a macro
           (including the case where the macro is expanded by an #if directive).
           Such usage is not portable.  This warning is also enabled by
           -Wpedantic and -Wextra.

       -Wunused-macros
           Warn about macros defined in the main file that are unused.  A macro
           is used if it is expanded or tested for existence at least once.  The
           preprocessor also warns if the macro has not been used at the time it
           is redefined or undefined.

           Built-in macros, macros defined on the command line, and macros
           defined in include files are not warned about.

           Note: If a macro is actually used, but only used in skipped
           conditional blocks, then the preprocessor reports it as unused.  To
           avoid the warning in such a case, you might improve the scope of the
           macro's definition by, for example, moving it into the first skipped
           block.  Alternatively, you could provide a dummy use with something
           like:

                   #if defined the_macro_causing_the_warning
                   #endif

       -Wno-endif-labels
           Do not warn whenever an "#else" or an "#endif" are followed by text.
           This sometimes happens in older programs with code of the form

                   #if FOO
                   ...
                   #else FOO
                   ...
                   #endif FOO

           The second and third "FOO" should be in comments.  This warning is on
           by default.

       -Wbad-function-cast (C and Objective-C only)
           Warn when a function call is cast to a non-matching type.  For
           example, warn if a call to a function returning an integer type is
           cast to a pointer type.

       -Wc90-c99-compat (C and Objective-C only)
           Warn about features not present in ISO C90, but present in ISO C99.
           For instance, warn about use of variable length arrays, "long long"
           type, "bool" type, compound literals, designated initializers, and so
           on.  This option is independent of the standards mode.  Warnings are
           disabled in the expression that follows "__extension__".

       -Wc99-c11-compat (C and Objective-C only)
           Warn about features not present in ISO C99, but present in ISO C11.
           For instance, warn about use of anonymous structures and unions,
           "_Atomic" type qualifier, "_Thread_local" storage-class specifier,
           "_Alignas" specifier, "Alignof" operator, "_Generic" keyword, and so
           on.  This option is independent of the standards mode.  Warnings are
           disabled in the expression that follows "__extension__".

       -Wc11-c2x-compat (C and Objective-C only)
           Warn about features not present in ISO C11, but present in ISO C2X.
           For instance, warn about omitting the string in "_Static_assert", use
           of [[]] syntax for attributes, use of decimal floating-point types,
           and so on.  This option is independent of the standards mode.
           Warnings are disabled in the expression that follows "__extension__".

       -Wc++-compat (C and Objective-C only)
           Warn about ISO C constructs that are outside of the common subset of
           ISO C and ISO C++, e.g. request for implicit conversion from "void *"
           to a pointer to non-"void" type.

       -Wc++11-compat (C++ and Objective-C++ only)
           Warn about C++ constructs whose meaning differs between ISO C++ 1998
           and ISO C++ 2011, e.g., identifiers in ISO C++ 1998 that are keywords
           in ISO C++ 2011.  This warning turns on -Wnarrowing and is enabled by
           -Wall.

       -Wc++14-compat (C++ and Objective-C++ only)
           Warn about C++ constructs whose meaning differs between ISO C++ 2011
           and ISO C++ 2014.  This warning is enabled by -Wall.

       -Wc++17-compat (C++ and Objective-C++ only)
           Warn about C++ constructs whose meaning differs between ISO C++ 2014
           and ISO C++ 2017.  This warning is enabled by -Wall.

       -Wc++20-compat (C++ and Objective-C++ only)
           Warn about C++ constructs whose meaning differs between ISO C++ 2017
           and ISO C++ 2020.  This warning is enabled by -Wall.

       -Wcast-qual
           Warn whenever a pointer is cast so as to remove a type qualifier from
           the target type.  For example, warn if a "const char *" is cast to an
           ordinary "char *".

           Also warn when making a cast that introduces a type qualifier in an
           unsafe way.  For example, casting "char **" to "const char **" is
           unsafe, as in this example:

                     /* p is char ** value.  */
                     const char **q = (const char **) p;
                     /* Assignment of readonly string to const char * is OK.  */
                     *q = "string";
                     /* Now char** pointer points to read-only memory.  */
                     **p = 'b';

       -Wcast-align
           Warn whenever a pointer is cast such that the required alignment of
           the target is increased.  For example, warn if a "char *" is cast to
           an "int *" on machines where integers can only be accessed at two- or
           four-byte boundaries.

       -Wcast-align=strict
           Warn whenever a pointer is cast such that the required alignment of
           the target is increased.  For example, warn if a "char *" is cast to
           an "int *" regardless of the target machine.

       -Wcast-function-type
           Warn when a function pointer is cast to an incompatible function
           pointer.  In a cast involving function types with a variable argument
           list only the types of initial arguments that are provided are
           considered.  Any parameter of pointer-type matches any other pointer-
           type.  Any benign differences in integral types are ignored, like
           "int" vs. "long" on ILP32 targets.  Likewise type qualifiers are
           ignored.  The function type "void (*) (void)" is special and matches
           everything, which can be used to suppress this warning.  In a cast
           involving pointer to member types this warning warns whenever the
           type cast is changing the pointer to member type.  This warning is
           enabled by -Wextra.

       -Wwrite-strings
           When compiling C, give string constants the type "const char[length]"
           so that copying the address of one into a non-"const" "char *"
           pointer produces a warning.  These warnings help you find at compile
           time code that can try to write into a string constant, but only if
           you have been very careful about using "const" in declarations and
           prototypes.  Otherwise, it is just a nuisance. This is why we did not
           make -Wall request these warnings.

           When compiling C++, warn about the deprecated conversion from string
           literals to "char *".  This warning is enabled by default for C++
           programs.

       -Wclobbered
           Warn for variables that might be changed by "longjmp" or "vfork".
           This warning is also enabled by -Wextra.

       -Wconversion
           Warn for implicit conversions that may alter a value. This includes
           conversions between real and integer, like "abs (x)" when "x" is
           "double"; conversions between signed and unsigned, like "unsigned ui
           = -1"; and conversions to smaller types, like "sqrtf (M_PI)". Do not
           warn for explicit casts like "abs ((int) x)" and "ui = (unsigned)
           -1", or if the value is not changed by the conversion like in "abs
           (2.0)".  Warnings about conversions between signed and unsigned
           integers can be disabled by using -Wno-sign-conversion.

           For C++, also warn for confusing overload resolution for user-defined
           conversions; and conversions that never use a type conversion
           operator: conversions to "void", the same type, a base class or a
           reference to them. Warnings about conversions between signed and
           unsigned integers are disabled by default in C++ unless
           -Wsign-conversion is explicitly enabled.

           Warnings about conversion from arithmetic on a small type back to
           that type are only given with -Warith-conversion.

       -Wdangling-else
           Warn about constructions where there may be confusion to which "if"
           statement an "else" branch belongs.  Here is an example of such a
           case:

                   {
                     if (a)
                       if (b)
                         foo ();
                     else
                       bar ();
                   }

           In C/C++, every "else" branch belongs to the innermost possible "if"
           statement, which in this example is "if (b)".  This is often not what
           the programmer expected, as illustrated in the above example by
           indentation the programmer chose.  When there is the potential for
           this confusion, GCC issues a warning when this flag is specified.  To
           eliminate the warning, add explicit braces around the innermost "if"
           statement so there is no way the "else" can belong to the enclosing
           "if".  The resulting code looks like this:

                   {
                     if (a)
                       {
                         if (b)
                           foo ();
                         else
                           bar ();
                       }
                   }

           This warning is enabled by -Wparentheses.

       -Wdate-time
           Warn when macros "__TIME__", "__DATE__" or "__TIMESTAMP__" are
           encountered as they might prevent bit-wise-identical reproducible
           compilations.

       -Wempty-body
           Warn if an empty body occurs in an "if", "else" or "do while"
           statement.  This warning is also enabled by -Wextra.

       -Wno-endif-labels
           Do not warn about stray tokens after "#else" and "#endif".

       -Wenum-compare
           Warn about a comparison between values of different enumerated types.
           In C++ enumerated type mismatches in conditional expressions are also
           diagnosed and the warning is enabled by default.  In C this warning
           is enabled by -Wall.

       -Wenum-conversion
           Warn when a value of enumerated type is implicitly converted to a
           different enumerated type.  This warning is enabled by -Wextra in C.

       -Wjump-misses-init (C, Objective-C only)
           Warn if a "goto" statement or a "switch" statement jumps forward
           across the initialization of a variable, or jumps backward to a label
           after the variable has been initialized.  This only warns about
           variables that are initialized when they are declared.  This warning
           is only supported for C and Objective-C; in C++ this sort of branch
           is an error in any case.

           -Wjump-misses-init is included in -Wc++-compat.  It can be disabled
           with the -Wno-jump-misses-init option.

       -Wsign-compare
           Warn when a comparison between signed and unsigned values could
           produce an incorrect result when the signed value is converted to
           unsigned.  In C++, this warning is also enabled by -Wall.  In C, it
           is also enabled by -Wextra.

       -Wsign-conversion
           Warn for implicit conversions that may change the sign of an integer
           value, like assigning a signed integer expression to an unsigned
           integer variable. An explicit cast silences the warning. In C, this
           option is enabled also by -Wconversion.

       -Wfloat-conversion
           Warn for implicit conversions that reduce the precision of a real
           value.  This includes conversions from real to integer, and from
           higher precision real to lower precision real values.  This option is
           also enabled by -Wconversion.

       -Wno-scalar-storage-order
           Do not warn on suspicious constructs involving reverse scalar storage
           order.

       -Wsizeof-array-div
           Warn about divisions of two sizeof operators when the first one is
           applied to an array and the divisor does not equal the size of the
           array element.  In such a case, the computation will not yield the
           number of elements in the array, which is likely what the user
           intended.  This warning warns e.g. about

                   int fn ()
                   {
                     int arr[10];
                     return sizeof (arr) / sizeof (short);
                   }

           This warning is enabled by -Wall.

       -Wsizeof-pointer-div
           Warn for suspicious divisions of two sizeof expressions that divide
           the pointer size by the element size, which is the usual way to
           compute the array size but won't work out correctly with pointers.
           This warning warns e.g. about "sizeof (ptr) / sizeof (ptr[0])" if
           "ptr" is not an array, but a pointer.  This warning is enabled by
           -Wall.

       -Wsizeof-pointer-memaccess
           Warn for suspicious length parameters to certain string and memory
           built-in functions if the argument uses "sizeof".  This warning
           triggers for example for "memset (ptr, 0, sizeof (ptr));" if "ptr" is
           not an array, but a pointer, and suggests a possible fix, or about
           "memcpy (&foo, ptr, sizeof (&foo));".  -Wsizeof-pointer-memaccess
           also warns about calls to bounded string copy functions like
           "strncat" or "strncpy" that specify as the bound a "sizeof"
           expression of the source array.  For example, in the following
           function the call to "strncat" specifies the size of the source
           string as the bound.  That is almost certainly a mistake and so the
           call is diagnosed.

                   void make_file (const char *name)
                   {
                     char path[PATH_MAX];
                     strncpy (path, name, sizeof path - 1);
                     strncat (path, ".text", sizeof ".text");
                     ...
                   }

           The -Wsizeof-pointer-memaccess option is enabled by -Wall.

       -Wno-sizeof-array-argument
           Do not warn when the "sizeof" operator is applied to a parameter that
           is declared as an array in a function definition.  This warning is
           enabled by default for C and C++ programs.

       -Wmemset-elt-size
           Warn for suspicious calls to the "memset" built-in function, if the
           first argument references an array, and the third argument is a
           number equal to the number of elements, but not equal to the size of
           the array in memory.  This indicates that the user has omitted a
           multiplication by the element size.  This warning is enabled by
           -Wall.

       -Wmemset-transposed-args
           Warn for suspicious calls to the "memset" built-in function where the
           second argument is not zero and the third argument is zero.  For
           example, the call "memset (buf, sizeof buf, 0)" is diagnosed because
           "memset (buf, 0, sizeof buf)" was meant instead.  The diagnostic is
           only emitted if the third argument is a literal zero.  Otherwise, if
           it is an expression that is folded to zero, or a cast of zero to some
           type, it is far less likely that the arguments have been mistakenly
           transposed and no warning is emitted.  This warning is enabled by
           -Wall.

       -Waddress
           Warn about suspicious uses of memory addresses. These include using
           the address of a function in a conditional expression, such as "void
           func(void); if (func)", and comparisons against the memory address of
           a string literal, such as "if (x == "abc")".  Such uses typically
           indicate a programmer error: the address of a function always
           evaluates to true, so their use in a conditional usually indicate
           that the programmer forgot the parentheses in a function call; and
           comparisons against string literals result in unspecified behavior
           and are not portable in C, so they usually indicate that the
           programmer intended to use "strcmp".  This warning is enabled by
           -Wall.

       -Wno-address-of-packed-member
           Do not warn when the address of packed member of struct or union is
           taken, which usually results in an unaligned pointer value.  This is
           enabled by default.

       -Wlogical-op
           Warn about suspicious uses of logical operators in expressions.  This
           includes using logical operators in contexts where a bit-wise
           operator is likely to be expected.  Also warns when the operands of a
           logical operator are the same:

                   extern int a;
                   if (a < 0 && a < 0) { ... }

       -Wlogical-not-parentheses
           Warn about logical not used on the left hand side operand of a
           comparison.  This option does not warn if the right operand is
           considered to be a boolean expression.  Its purpose is to detect
           suspicious code like the following:

                   int a;
                   ...
                   if (!a > 1) { ... }

           It is possible to suppress the warning by wrapping the LHS into
           parentheses:

                   if ((!a) > 1) { ... }

           This warning is enabled by -Wall.

       -Waggregate-return
           Warn if any functions that return structures or unions are defined or
           called.  (In languages where you can return an array, this also
           elicits a warning.)

       -Wno-aggressive-loop-optimizations
           Warn if in a loop with constant number of iterations the compiler
           detects undefined behavior in some statement during one or more of
           the iterations.

       -Wno-attributes
           Do not warn if an unexpected "__attribute__" is used, such as
           unrecognized attributes, function attributes applied to variables,
           etc.  This does not stop errors for incorrect use of supported
           attributes.

       -Wno-builtin-declaration-mismatch
           Warn if a built-in function is declared with an incompatible
           signature or as a non-function, or when a built-in function declared
           with a type that does not include a prototype is called with
           arguments whose promoted types do not match those expected by the
           function.  When -Wextra is specified, also warn when a built-in
           function that takes arguments is declared without a prototype.  The
           -Wbuiltin-declaration-mismatch warning is enabled by default.  To
           avoid the warning include the appropriate header to bring the
           prototypes of built-in functions into scope.

           For example, the call to "memset" below is diagnosed by the warning
           because the function expects a value of type "size_t" as its argument
           but the type of 32 is "int".  With -Wextra, the declaration of the
           function is diagnosed as well.

                   extern void* memset ();
                   void f (void *d)
                   {
                     memset (d, '\0', 32);
                   }

       -Wno-builtin-macro-redefined
           Do not warn if certain built-in macros are redefined.  This
           suppresses warnings for redefinition of "__TIMESTAMP__", "__TIME__",
           "__DATE__", "__FILE__", and "__BASE_FILE__".

       -Wstrict-prototypes (C and Objective-C only)
           Warn if a function is declared or defined without specifying the
           argument types.  (An old-style function definition is permitted
           without a warning if preceded by a declaration that specifies the
           argument types.)

       -Wold-style-declaration (C and Objective-C only)
           Warn for obsolescent usages, according to the C Standard, in a
           declaration. For example, warn if storage-class specifiers like
           "static" are not the first things in a declaration.  This warning is
           also enabled by -Wextra.

       -Wold-style-definition (C and Objective-C only)
           Warn if an old-style function definition is used.  A warning is given
           even if there is a previous prototype.  A definition using () is not
           considered an old-style definition in C2X mode, because it is
           equivalent to (void) in that case, but is considered an old-style
           definition for older standards.

       -Wmissing-parameter-type (C and Objective-C only)
           A function parameter is declared without a type specifier in
           K&R-style functions:

                   void foo(bar) { }

           This warning is also enabled by -Wextra.

       -Wmissing-prototypes (C and Objective-C only)
           Warn if a global function is defined without a previous prototype
           declaration.  This warning is issued even if the definition itself
           provides a prototype.  Use this option to detect global functions
           that do not have a matching prototype declaration in a header file.
           This option is not valid for C++ because all function declarations
           provide prototypes and a non-matching declaration declares an
           overload rather than conflict with an earlier declaration.  Use
           -Wmissing-declarations to detect missing declarations in C++.

       -Wmissing-declarations
           Warn if a global function is defined without a previous declaration.
           Do so even if the definition itself provides a prototype.  Use this
           option to detect global functions that are not declared in header
           files.  In C, no warnings are issued for functions with previous non-
           prototype declarations; use -Wmissing-prototypes to detect missing
           prototypes.  In C++, no warnings are issued for function templates,
           or for inline functions, or for functions in anonymous namespaces.

       -Wmissing-field-initializers
           Warn if a structure's initializer has some fields missing.  For
           example, the following code causes such a warning, because "x.h" is
           implicitly zero:

                   struct s { int f, g, h; };
                   struct s x = { 3, 4 };

           This option does not warn about designated initializers, so the
           following modification does not trigger a warning:

                   struct s { int f, g, h; };
                   struct s x = { .f = 3, .g = 4 };

           In C this option does not warn about the universal zero initializer {
           0 }:

                   struct s { int f, g, h; };
                   struct s x = { 0 };

           Likewise, in C++ this option does not warn about the empty { }
           initializer, for example:

                   struct s { int f, g, h; };
                   s x = { };

           This warning is included in -Wextra.  To get other -Wextra warnings
           without this one, use -Wextra -Wno-missing-field-initializers.

       -Wno-multichar
           Do not warn if a multicharacter constant ('FOOF') is used.  Usually
           they indicate a typo in the user's code, as they have implementation-
           defined values, and should not be used in portable code.

       -Wnormalized=[none|id|nfc|nfkc]
           In ISO C and ISO C++, two identifiers are different if they are
           different sequences of characters.  However, sometimes when
           characters outside the basic ASCII character set are used, you can
           have two different character sequences that look the same.  To avoid
           confusion, the ISO 10646 standard sets out some normalization rules
           which when applied ensure that two sequences that look the same are
           turned into the same sequence.  GCC can warn you if you are using
           identifiers that have not been normalized; this option controls that
           warning.

           There are four levels of warning supported by GCC.  The default is
           -Wnormalized=nfc, which warns about any identifier that is not in the
           ISO 10646 "C" normalized form, NFC.  NFC is the recommended form for
           most uses.  It is equivalent to -Wnormalized.

           Unfortunately, there are some characters allowed in identifiers by
           ISO C and ISO C++ that, when turned into NFC, are not allowed in
           identifiers.  That is, there's no way to use these symbols in
           portable ISO C or C++ and have all your identifiers in NFC.
           -Wnormalized=id suppresses the warning for these characters.  It is
           hoped that future versions of the standards involved will correct
           this, which is why this option is not the default.

           You can switch the warning off for all characters by writing
           -Wnormalized=none or -Wno-normalized.  You should only do this if you
           are using some other normalization scheme (like "D"), because
           otherwise you can easily create bugs that are literally impossible to
           see.

           Some characters in ISO 10646 have distinct meanings but look
           identical in some fonts or display methodologies, especially once
           formatting has been applied.  For instance "\u207F", "SUPERSCRIPT
           LATIN SMALL LETTER N", displays just like a regular "n" that has been
           placed in a superscript.  ISO 10646 defines the NFKC normalization
           scheme to convert all these into a standard form as well, and GCC
           warns if your code is not in NFKC if you use -Wnormalized=nfkc.  This
           warning is comparable to warning about every identifier that contains
           the letter O because it might be confused with the digit 0, and so is
           not the default, but may be useful as a local coding convention if
           the programming environment cannot be fixed to display these
           characters distinctly.

       -Wno-attribute-warning
           Do not warn about usage of functions declared with "warning"
           attribute.  By default, this warning is enabled.
           -Wno-attribute-warning can be used to disable the warning or
           -Wno-error=attribute-warning can be used to disable the error when
           compiled with -Werror flag.

       -Wno-deprecated
           Do not warn about usage of deprecated features.

       -Wno-deprecated-declarations
           Do not warn about uses of functions, variables, and types marked as
           deprecated by using the "deprecated" attribute.

       -Wno-overflow
           Do not warn about compile-time overflow in constant expressions.

       -Wno-odr
           Warn about One Definition Rule violations during link-time
           optimization.  Enabled by default.

       -Wopenmp-simd
           Warn if the vectorizer cost model overrides the OpenMP simd directive
           set by user.  The -fsimd-cost-model=unlimited option can be used to
           relax the cost model.

       -Woverride-init (C and Objective-C only)
           Warn if an initialized field without side effects is overridden when
           using designated initializers.

           This warning is included in -Wextra.  To get other -Wextra warnings
           without this one, use -Wextra -Wno-override-init.

       -Wno-override-init-side-effects (C and Objective-C only)
           Do not warn if an initialized field with side effects is overridden
           when using designated initializers.  This warning is enabled by
           default.

       -Wpacked
           Warn if a structure is given the packed attribute, but the packed
           attribute has no effect on the layout or size of the structure.  Such
           structures may be mis-aligned for little benefit.  For instance, in
           this code, the variable "f.x" in "struct bar" is misaligned even
           though "struct bar" does not itself have the packed attribute:

                   struct foo {
                     int x;
                     char a, b, c, d;
                   } __attribute__((packed));
                   struct bar {
                     char z;
                     struct foo f;
                   };

       -Wnopacked-bitfield-compat
           The 4.1, 4.2 and 4.3 series of GCC ignore the "packed" attribute on
           bit-fields of type "char".  This was fixed in GCC 4.4 but the change
           can lead to differences in the structure layout.  GCC informs you
           when the offset of such a field has changed in GCC 4.4.  For example
           there is no longer a 4-bit padding between field "a" and "b" in this
           structure:

                   struct foo
                   {
                     char a:4;
                     char b:8;
                   } __attribute__ ((packed));

           This warning is enabled by default.  Use -Wno-packed-bitfield-compat
           to disable this warning.

       -Wpacked-not-aligned (C, C++, Objective-C and Objective-C++ only)
           Warn if a structure field with explicitly specified alignment in a
           packed struct or union is misaligned.  For example, a warning will be
           issued on "struct S", like, "warning: alignment 1 of 'struct S' is
           less than 8", in this code:

                   struct __attribute__ ((aligned (8))) S8 { char a[8]; };
                   struct __attribute__ ((packed)) S {
                     struct S8 s8;
                   };

           This warning is enabled by -Wall.

       -Wpadded
           Warn if padding is included in a structure, either to align an
           element of the structure or to align the whole structure.  Sometimes
           when this happens it is possible to rearrange the fields of the
           structure to reduce the padding and so make the structure smaller.

       -Wredundant-decls
           Warn if anything is declared more than once in the same scope, even
           in cases where multiple declaration is valid and changes nothing.

       -Wrestrict
           Warn when an object referenced by a "restrict"-qualified parameter
           (or, in C++, a "__restrict"-qualified parameter) is aliased by
           another argument, or when copies between such objects overlap.  For
           example, the call to the "strcpy" function below attempts to truncate
           the string by replacing its initial characters with the last four.
           However, because the call writes the terminating NUL into "a[4]", the
           copies overlap and the call is diagnosed.

                   void foo (void)
                   {
                     char a[] = "abcd1234";
                     strcpy (a, a + 4);
                     ...
                   }

           The -Wrestrict option detects some instances of simple overlap even
           without optimization but works best at -O2 and above.  It is included
           in -Wall.

       -Wnested-externs (C and Objective-C only)
           Warn if an "extern" declaration is encountered within a function.

       -Winline
           Warn if a function that is declared as inline cannot be inlined.
           Even with this option, the compiler does not warn about failures to
           inline functions declared in system headers.

           The compiler uses a variety of heuristics to determine whether or not
           to inline a function.  For example, the compiler takes into account
           the size of the function being inlined and the amount of inlining
           that has already been done in the current function.  Therefore,
           seemingly insignificant changes in the source program can cause the
           warnings produced by -Winline to appear or disappear.

       -Wint-in-bool-context
           Warn for suspicious use of integer values where boolean values are
           expected, such as conditional expressions (?:) using non-boolean
           integer constants in boolean context, like "if (a <= b ? 2 : 3)".  Or
           left shifting of signed integers in boolean context, like "for (a =
           0; 1 << a; a++);".  Likewise for all kinds of multiplications
           regardless of the data type.  This warning is enabled by -Wall.

       -Wno-int-to-pointer-cast
           Suppress warnings from casts to pointer type of an integer of a
           different size. In C++, casting to a pointer type of smaller size is
           an error. Wint-to-pointer-cast is enabled by default.

       -Wno-pointer-to-int-cast (C and Objective-C only)
           Suppress warnings from casts from a pointer to an integer type of a
           different size.

       -Winvalid-pch
           Warn if a precompiled header is found in the search path but cannot
           be used.

       -Wlong-long
           Warn if "long long" type is used.  This is enabled by either
           -Wpedantic or -Wtraditional in ISO C90 and C++98 modes.  To inhibit
           the warning messages, use -Wno-long-long.

       -Wvariadic-macros
           Warn if variadic macros are used in ISO C90 mode, or if the GNU
           alternate syntax is used in ISO C99 mode.  This is enabled by either
           -Wpedantic or -Wtraditional.  To inhibit the warning messages, use
           -Wno-variadic-macros.

       -Wno-varargs
           Do not warn upon questionable usage of the macros used to handle
           variable arguments like "va_start".  These warnings are enabled by
           default.

       -Wvector-operation-performance
           Warn if vector operation is not implemented via SIMD capabilities of
           the architecture.  Mainly useful for the performance tuning.  Vector
           operation can be implemented "piecewise", which means that the scalar
           operation is performed on every vector element; "in parallel", which
           means that the vector operation is implemented using scalars of wider
           type, which normally is more performance efficient; and "as a single
           scalar", which means that vector fits into a scalar type.

       -Wvla
           Warn if a variable-length array is used in the code.  -Wno-vla
           prevents the -Wpedantic warning of the variable-length array.

       -Wvla-larger-than=byte-size
           If this option is used, the compiler warns for declarations of
           variable-length arrays whose size is either unbounded, or bounded by
           an argument that allows the array size to exceed byte-size bytes.
           This is similar to how -Walloca-larger-than=byte-size works, but with
           variable-length arrays.

           Note that GCC may optimize small variable-length arrays of a known
           value into plain arrays, so this warning may not get triggered for
           such arrays.

           -Wvla-larger-than=PTRDIFF_MAX is enabled by default but is typically
           only effective when -ftree-vrp is active (default for -O2 and above).

           See also -Walloca-larger-than=byte-size.

       -Wno-vla-larger-than
           Disable -Wvla-larger-than= warnings.  The option is equivalent to
           -Wvla-larger-than=SIZE_MAX or larger.

       -Wvla-parameter
           Warn about redeclarations of functions involving arguments of
           Variable Length Array types of inconsistent kinds or forms, and
           enable the detection of out-of-bounds accesses to such parameters by
           warnings such as -Warray-bounds.

           If the first function declaration uses the VLA form the bound
           specified in the array is assumed to be the minimum number of
           elements expected to be provided in calls to the function and the
           maximum number of elements accessed by it.  Failing to provide
           arguments of sufficient size or accessing more than the maximum
           number of elements may be diagnosed.

           For example, the warning triggers for the following redeclarations
           because the first one allows an array of any size to be passed to "f"
           while the second one specifies that the array argument must have at
           least "n" elements.  In addition, calling "f" with the assotiated VLA
           bound parameter in excess of the actual VLA bound triggers a warning
           as well.

                   void f (int n, int[n]);
                   void f (int, int[]);     // warning: argument 2 previously declared as a VLA

                   void g (int n)
                   {
                       if (n > 4)
                         return;
                       int a[n];
                       f (sizeof a, a);     // warning: access to a by f may be out of bounds
                     ...
                   }

           -Wvla-parameter is included in -Wall.  The -Warray-parameter option
           triggers warnings for similar problems involving ordinary array
           arguments.

       -Wvolatile-register-var
           Warn if a register variable is declared volatile.  The volatile
           modifier does not inhibit all optimizations that may eliminate reads
           and/or writes to register variables.  This warning is enabled by
           -Wall.

       -Wdisabled-optimization
           Warn if a requested optimization pass is disabled.  This warning does
           not generally indicate that there is anything wrong with your code;
           it merely indicates that GCC's optimizers are unable to handle the
           code effectively.  Often, the problem is that your code is too big or
           too complex; GCC refuses to optimize programs when the optimization
           itself is likely to take inordinate amounts of time.

       -Wpointer-sign (C and Objective-C only)
           Warn for pointer argument passing or assignment with different
           signedness.  This option is only supported for C and Objective-C.  It
           is implied by -Wall and by -Wpedantic, which can be disabled with
           -Wno-pointer-sign.

       -Wstack-protector
           This option is only active when -fstack-protector is active.  It
           warns about functions that are not protected against stack smashing.

       -Woverlength-strings
           Warn about string constants that are longer than the "minimum
           maximum" length specified in the C standard.  Modern compilers
           generally allow string constants that are much longer than the
           standard's minimum limit, but very portable programs should avoid
           using longer strings.

           The limit applies after string constant concatenation, and does not
           count the trailing NUL.  In C90, the limit was 509 characters; in
           C99, it was raised to 4095.  C++98 does not specify a normative
           minimum maximum, so we do not diagnose overlength strings in C++.

           This option is implied by -Wpedantic, and can be disabled with
           -Wno-overlength-strings.

       -Wunsuffixed-float-constants (C and Objective-C only)
           Issue a warning for any floating constant that does not have a
           suffix.  When used together with -Wsystem-headers it warns about such
           constants in system header files.  This can be useful when preparing
           code to use with the "FLOAT_CONST_DECIMAL64" pragma from the decimal
           floating-point extension to C99.

       -Wno-lto-type-mismatch
           During the link-time optimization, do not warn about type mismatches
           in global declarations from different compilation units.  Requires
           -flto to be enabled.  Enabled by default.

       -Wno-designated-init (C and Objective-C only)
           Suppress warnings when a positional initializer is used to initialize
           a structure that has been marked with the "designated_init"
           attribute.

   Options That Control Static Analysis
       -fanalyzer
           This option enables an static analysis of program flow which looks
           for "interesting" interprocedural paths through the code, and issues
           warnings for problems found on them.

           This analysis is much more expensive than other GCC warnings.

           Enabling this option effectively enables the following warnings:

           -Wanalyzer-double-fclose -Wanalyzer-double-free
           -Wanalyzer-exposure-through-output-file -Wanalyzer-file-leak
           -Wanalyzer-free-of-non-heap -Wanalyzer-malloc-leak
           -Wanalyzer-mismatching-deallocation -Wanalyzer-possible-null-argument
           -Wanalyzer-possible-null-dereference -Wanalyzer-null-argument
           -Wanalyzer-null-dereference -Wanalyzer-shift-count-negative
           -Wanalyzer-shift-count-overflow -Wanalyzer-stale-setjmp-buffer
           -Wanalyzer-tainted-array-index
           -Wanalyzer-unsafe-call-within-signal-handler
           -Wanalyzer-use-after-free
           -Wanalyzer-use-of-pointer-in-stale-stack-frame
           -Wanalyzer-write-to-const -Wanalyzer-write-to-string-literal

           This option is only available if GCC was configured with analyzer
           support enabled.

       -Wanalyzer-too-complex
           If -fanalyzer is enabled, the analyzer uses various heuristics to
           attempt to explore the control flow and data flow in the program, but
           these can be defeated by sufficiently complicated code.

           By default, the analysis silently stops if the code is too
           complicated for the analyzer to fully explore and it reaches an
           internal limit.  The -Wanalyzer-too-complex option warns if this
           occurs.

       -Wno-analyzer-double-fclose
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-double-fclose to disable it.

           This diagnostic warns for paths through the code in which a "FILE *"
           can have "fclose" called on it more than once.

       -Wno-analyzer-double-free
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-double-free to disable it.

           This diagnostic warns for paths through the code in which a pointer
           can have a deallocator called on it more than once, either "free", or
           a deallocator referenced by attribute "malloc".

       -Wno-analyzer-exposure-through-output-file
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-exposure-through-output-file to disable it.

           This diagnostic warns for paths through the code in which a security-
           sensitive value is written to an output file (such as writing a
           password to a log file).

       -Wno-analyzer-file-leak
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-file-leak to disable it.

           This diagnostic warns for paths through the code in which a
           "<stdio.h>" "FILE *" stream object is leaked.

       -Wno-analyzer-free-of-non-heap
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-free-of-non-heap to disable it.

           This diagnostic warns for paths through the code in which "free" is
           called on a non-heap pointer (e.g. an on-stack buffer, or a global).

       -Wno-analyzer-malloc-leak
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-malloc-leak to disable it.

           This diagnostic warns for paths through the code in which a pointer
           allocated via an allocator is leaked: either "malloc", or a function
           marked with attribute "malloc".

       -Wno-analyzer-mismatching-deallocation
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-mismatching-deallocation to disable it.

           This diagnostic warns for paths through the code in which the wrong
           deallocation function is called on a pointer value, based on which
           function was used to allocate the pointer value.  The diagnostic will
           warn about mismatches between "free", scalar "delete" and vector
           "delete[]", and those marked as allocator/deallocator pairs using
           attribute "malloc".

       -Wno-analyzer-possible-null-argument
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-possible-null-argument to disable it.

           This diagnostic warns for paths through the code in which a possibly-
           NULL value is passed to a function argument marked with
           "__attribute__((nonnull))" as requiring a non-NULL value.

       -Wno-analyzer-possible-null-dereference
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-possible-null-dereference to disable it.

           This diagnostic warns for paths through the code in which a possibly-
           NULL value is dereferenced.

       -Wno-analyzer-null-argument
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-null-argument to disable it.

           This diagnostic warns for paths through the code in which a value
           known to be NULL is passed to a function argument marked with
           "__attribute__((nonnull))" as requiring a non-NULL value.

       -Wno-analyzer-null-dereference
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-null-dereference to disable it.

           This diagnostic warns for paths through the code in which a value
           known to be NULL is dereferenced.

       -Wno-analyzer-shift-count-negative
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-shift-count-negative to disable it.

           This diagnostic warns for paths through the code in which a shift is
           attempted with a negative count.  It is analogous to the
           -Wshift-count-negative diagnostic implemented in the C/C++ front
           ends, but is implemented based on analyzing interprocedural paths,
           rather than merely parsing the syntax tree.  However, the analyzer
           does not prioritize detection of such paths, so false negatives are
           more likely relative to other warnings.

       -Wno-analyzer-shift-count-overflow
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-shift-count-overflow to disable it.

           This diagnostic warns for paths through the code in which a shift is
           attempted with a count greater than or equal to the precision of the
           operand's type.  It is analogous to the -Wshift-count-overflow
           diagnostic implemented in the C/C++ front ends, but is implemented
           based on analyzing interprocedural paths, rather than merely parsing
           the syntax tree.  However, the analyzer does not prioritize detection
           of such paths, so false negatives are more likely relative to other
           warnings.

       -Wno-analyzer-stale-setjmp-buffer
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-stale-setjmp-buffer to disable it.

           This diagnostic warns for paths through the code in which "longjmp"
           is called to rewind to a "jmp_buf" relating to a "setjmp" call in a
           function that has returned.

           When "setjmp" is called on a "jmp_buf" to record a rewind location,
           it records the stack frame.  The stack frame becomes invalid when the
           function containing the "setjmp" call returns.  Attempting to rewind
           to it via "longjmp" would reference a stack frame that no longer
           exists, and likely lead to a crash (or worse).

       -Wno-analyzer-tainted-array-index
           This warning requires both -fanalyzer and -fanalyzer-checker=taint to
           enable it; use -Wno-analyzer-tainted-array-index to disable it.

           This diagnostic warns for paths through the code in which a value
           that could be under an attacker's control is used as the index of an
           array access without being sanitized.

       -Wno-analyzer-unsafe-call-within-signal-handler
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-unsafe-call-within-signal-handler to disable it.

           This diagnostic warns for paths through the code in which a function
           known to be async-signal-unsafe (such as "fprintf") is called from a
           signal handler.

       -Wno-analyzer-use-after-free
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-use-after-free to disable it.

           This diagnostic warns for paths through the code in which a pointer
           is used after a deallocator is called on it: either "free", or a
           deallocator referenced by attribute "malloc".

       -Wno-analyzer-use-of-pointer-in-stale-stack-frame
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-use-of-pointer-in-stale-stack-frame to disable it.

           This diagnostic warns for paths through the code in which a pointer
           is dereferenced that points to a variable in a stale stack frame.

       -Wno-analyzer-write-to-const
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-write-to-const to disable it.

           This diagnostic warns for paths through the code in which the
           analyzer detects an attempt to write through a pointer to a "const"
           object.  However, the analyzer does not prioritize detection of such
           paths, so false negatives are more likely relative to other warnings.

       -Wno-analyzer-write-to-string-literal
           This warning requires -fanalyzer, which enables it; use
           -Wno-analyzer-write-to-string-literal to disable it.

           This diagnostic warns for paths through the code in which the
           analyzer detects an attempt to write through a pointer to a string
           literal.  However, the analyzer does not prioritize detection of such
           paths, so false negatives are more likely relative to other warnings.

       Pertinent parameters for controlling the exploration are: --param
       analyzer-bb-explosion-factor=value, --param
       analyzer-max-enodes-per-program-point=value, --param
       analyzer-max-recursion-depth=value, and --param
       analyzer-min-snodes-for-call-summary=value.

       The following options control the analyzer.

       -fanalyzer-call-summaries
           Simplify interprocedural analysis by computing the effect of certain
           calls, rather than exploring all paths through the function from
           callsite to each possible return.

           If enabled, call summaries are only used for functions with more than
           one call site, and that are sufficiently complicated (as per --param
           analyzer-min-snodes-for-call-summary=value).

       -fanalyzer-checker=name
           Restrict the analyzer to run just the named checker, and enable it.

           Some checkers are disabled by default (even with -fanalyzer), such as
           the "taint" checker that implements -Wanalyzer-tainted-array-index,
           and this option is required to enable them.

       -fno-analyzer-feasibility
           This option is intended for analyzer developers.

           By default the analyzer verifies that there is a feasible control
           flow path for each diagnostic it emits: that the conditions that hold
           are not mutually exclusive.  Diagnostics for which no feasible path
           can be found are rejected.  This filtering can be suppressed with
           -fno-analyzer-feasibility, for debugging issues in this code.

       -fanalyzer-fine-grained
           This option is intended for analyzer developers.

           Internally the analyzer builds an "exploded graph" that combines
           control flow graphs with data flow information.

           By default, an edge in this graph can contain the effects of a run of
           multiple statements within a basic block.  With
           -fanalyzer-fine-grained, each statement gets its own edge.

       -fanalyzer-show-duplicate-count
           This option is intended for analyzer developers: if multiple
           diagnostics have been detected as being duplicates of each other, it
           emits a note when reporting the best diagnostic, giving the number of
           additional diagnostics that were suppressed by the deduplication
           logic.

       -fno-analyzer-state-merge
           This option is intended for analyzer developers.

           By default the analyzer attempts to simplify analysis by merging
           sufficiently similar states at each program point as it builds its
           "exploded graph".  With -fno-analyzer-state-merge this merging can be
           suppressed, for debugging state-handling issues.

       -fno-analyzer-state-purge
           This option is intended for analyzer developers.

           By default the analyzer attempts to simplify analysis by purging
           aspects of state at a program point that appear to no longer be
           relevant e.g. the values of locals that aren't accessed later in the
           function and which aren't relevant to leak analysis.

           With -fno-analyzer-state-purge this purging of state can be
           suppressed, for debugging state-handling issues.

       -fanalyzer-transitivity
           This option enables transitivity of constraints within the analyzer.

       -fanalyzer-verbose-edges
           This option is intended for analyzer developers.  It enables more
           verbose, lower-level detail in the descriptions of control flow
           within diagnostic paths.

       -fanalyzer-verbose-state-changes
           This option is intended for analyzer developers.  It enables more
           verbose, lower-level detail in the descriptions of events relating to
           state machines within diagnostic paths.

       -fanalyzer-verbosity=level
           This option controls the complexity of the control flow paths that
           are emitted for analyzer diagnostics.

           The level can be one of:

           0   At this level, interprocedural call and return events are
               displayed, along with the most pertinent state-change events
               relating to a diagnostic.  For example, for a double-"free"
               diagnostic, both calls to "free" will be shown.

           1   As per the previous level, but also show events for the entry to
               each function.

           2   As per the previous level, but also show events relating to
               control flow that are significant to triggering the issue (e.g.
               "true path taken" at a conditional).

               This level is the default.

           3   As per the previous level, but show all control flow events, not
               just significant ones.

           4   This level is intended for analyzer developers; it adds various
               other events intended for debugging the analyzer.

       -fdump-analyzer
           Dump internal details about what the analyzer is doing to
           file.analyzer.txt.  This option is overridden by
           -fdump-analyzer-stderr.

       -fdump-analyzer-stderr
           Dump internal details about what the analyzer is doing to stderr.
           This option overrides -fdump-analyzer.

       -fdump-analyzer-callgraph
           Dump a representation of the call graph suitable for viewing with
           GraphViz to file.callgraph.dot.

       -fdump-analyzer-exploded-graph
           Dump a representation of the "exploded graph" suitable for viewing
           with GraphViz to file.eg.dot.  Nodes are color-coded based on state-
           machine states to emphasize state changes.

       -fdump-analyzer-exploded-nodes
           Emit diagnostics showing where nodes in the "exploded graph" are in
           relation to the program source.

       -fdump-analyzer-exploded-nodes-2
           Dump a textual representation of the "exploded graph" to file.eg.txt.

       -fdump-analyzer-exploded-nodes-3
           Dump a textual representation of the "exploded graph" to one dump
           file per node, to file.eg-id.txt.  This is typically a large number
           of dump files.

       -fdump-analyzer-feasibility
           Dump internal details about the analyzer's search for feasible paths.
           The details are written in a form suitable for viewing with GraphViz
           to filenames of the form file.*.fg.dot and file.*.tg.dot.

       -fdump-analyzer-json
           Dump a compressed JSON representation of analyzer internals to
           file.analyzer.json.gz.  The precise format is subject to change.

       -fdump-analyzer-state-purge
           As per -fdump-analyzer-supergraph, dump a representation of the
           "supergraph" suitable for viewing with GraphViz, but annotate the
           graph with information on what state will be purged at each node.
           The graph is written to file.state-purge.dot.

       -fdump-analyzer-supergraph
           Dump representations of the "supergraph" suitable for viewing with
           GraphViz to file.supergraph.dot and to file.supergraph-eg.dot.  These
           show all of the control flow graphs in the program, with
           interprocedural edges for calls and returns.  The second dump
           contains annotations showing nodes in the "exploded graph" and
           diagnostics associated with them.

   Options for Debugging Your Program
       To tell GCC to emit extra information for use by a debugger, in almost
       all cases you need only to add -g to your other options.

       GCC allows you to use -g with -O.  The shortcuts taken by optimized code
       may occasionally be surprising: some variables you declared may not exist
       at all; flow of control may briefly move where you did not expect it;
       some statements may not be executed because they compute constant results
       or their values are already at hand; some statements may execute in
       different places because they have been moved out of loops.  Nevertheless
       it is possible to debug optimized output.  This makes it reasonable to
       use the optimizer for programs that might have bugs.

       If you are not using some other optimization option, consider using -Og
       with -g.  With no -O option at all, some compiler passes that collect
       information useful for debugging do not run at all, so that -Og may
       result in a better debugging experience.

       -g  Produce debugging information in the operating system's native format
           (stabs, COFF, XCOFF, or DWARF).  GDB can work with this debugging
           information.

           On most systems that use stabs format, -g enables use of extra
           debugging information that only GDB can use; this extra information
           makes debugging work better in GDB but probably makes other debuggers
           crash or refuse to read the program.  If you want to control for
           certain whether to generate the extra information, use -gstabs+,
           -gstabs, -gxcoff+, -gxcoff, or -gvms (see below).

       -ggdb
           Produce debugging information for use by GDB.  This means to use the
           most expressive format available (DWARF, stabs, or the native format
           if neither of those are supported), including GDB extensions if at
           all possible.

       -gdwarf
       -gdwarf-version
           Produce debugging information in DWARF format (if that is supported).
           The value of version may be either 2, 3, 4 or 5; the default version
           for most targets is 5 (with the exception of VxWorks, TPF and
           Darwin/Mac OS X, which default to version 2, and AIX, which defaults
           to version 4).

           Note that with DWARF Version 2, some ports require and always use
           some non-conflicting DWARF 3 extensions in the unwind tables.

           Version 4 may require GDB 7.0 and -fvar-tracking-assignments for
           maximum benefit. Version 5 requires GDB 8.0 or higher.

           GCC no longer supports DWARF Version 1, which is substantially
           different than Version 2 and later.  For historical reasons, some
           other DWARF-related options such as -fno-dwarf2-cfi-asm) retain a
           reference to DWARF Version 2 in their names, but apply to all
           currently-supported versions of DWARF.

       -gstabs
           Produce debugging information in stabs format (if that is supported),
           without GDB extensions.  This is the format used by DBX on most BSD
           systems.  On MIPS, Alpha and System V Release 4 systems this option
           produces stabs debugging output that is not understood by DBX.  On
           System V Release 4 systems this option requires the GNU assembler.

       -gstabs+
           Produce debugging information in stabs format (if that is supported),
           using GNU extensions understood only by the GNU debugger (GDB).  The
           use of these extensions is likely to make other debuggers crash or
           refuse to read the program.

       -gxcoff
           Produce debugging information in XCOFF format (if that is supported).
           This is the format used by the DBX debugger on IBM RS/6000 systems.

       -gxcoff+
           Produce debugging information in XCOFF format (if that is supported),
           using GNU extensions understood only by the GNU debugger (GDB).  The
           use of these extensions is likely to make other debuggers crash or
           refuse to read the program, and may cause assemblers other than the
           GNU assembler (GAS) to fail with an error.

       -gvms
           Produce debugging information in Alpha/VMS debug format (if that is
           supported).  This is the format used by DEBUG on Alpha/VMS systems.

       -glevel
       -ggdblevel
       -gstabslevel
       -gxcofflevel
       -gvmslevel
           Request debugging information and also use level to specify how much
           information.  The default level is 2.

           Level 0 produces no debug information at all.  Thus, -g0 negates -g.

           Level 1 produces minimal information, enough for making backtraces in
           parts of the program that you don't plan to debug.  This includes
           descriptions of functions and external variables, and line number
           tables, but no information about local variables.

           Level 3 includes extra information, such as all the macro definitions
           present in the program.  Some debuggers support macro expansion when
           you use -g3.

           If you use multiple -g options, with or without level numbers, the
           last such option is the one that is effective.

           -gdwarf does not accept a concatenated debug level, to avoid
           confusion with -gdwarf-level.  Instead use an additional -glevel
           option to change the debug level for DWARF.

       -fno-eliminate-unused-debug-symbols
           By default, no debug information is produced for symbols that are not
           actually used. Use this option if you want debug information for all
           symbols.

       -femit-class-debug-always
           Instead of emitting debugging information for a C++ class in only one
           object file, emit it in all object files using the class.  This
           option should be used only with debuggers that are unable to handle
           the way GCC normally emits debugging information for classes because
           using this option increases the size of debugging information by as
           much as a factor of two.

       -fno-merge-debug-strings
           Direct the linker to not merge together strings in the debugging
           information that are identical in different object files.  Merging is
           not supported by all assemblers or linkers.  Merging decreases the
           size of the debug information in the output file at the cost of
           increasing link processing time.  Merging is enabled by default.

       -fdebug-prefix-map=old=new
           When compiling files residing in directory old, record debugging
           information describing them as if the files resided in directory new
           instead.  This can be used to replace a build-time path with an
           install-time path in the debug info.  It can also be used to change
           an absolute path to a relative path by using . for new.  This can
           give more reproducible builds, which are location independent, but
           may require an extra command to tell GDB where to find the source
           files. See also -ffile-prefix-map.

       -fvar-tracking
           Run variable tracking pass.  It computes where variables are stored
           at each position in code.  Better debugging information is then
           generated (if the debugging information format supports this
           information).

           It is enabled by default when compiling with optimization (-Os, -O,
           -O2, ...), debugging information (-g) and the debug info format
           supports it.

       -fvar-tracking-assignments
           Annotate assignments to user variables early in the compilation and
           attempt to carry the annotations over throughout the compilation all
           the way to the end, in an attempt to improve debug information while
           optimizing.  Use of -gdwarf-4 is recommended along with it.

           It can be enabled even if var-tracking is disabled, in which case
           annotations are created and maintained, but discarded at the end.  By
           default, this flag is enabled together with -fvar-tracking, except
           when selective scheduling is enabled.

       -gsplit-dwarf
           If DWARF debugging information is enabled, separate as much debugging
           information as possible into a separate output file with the
           extension .dwo.  This option allows the build system to avoid linking
           files with debug information.  To be useful, this option requires a
           debugger capable of reading .dwo files.

       -gdwarf32
       -gdwarf64
           If DWARF debugging information is enabled, the -gdwarf32 selects the
           32-bit DWARF format and the -gdwarf64 selects the 64-bit DWARF
           format.  The default is target specific, on most targets it is
           -gdwarf32 though.  The 32-bit DWARF format is smaller, but can't
           support more than 2GiB of debug information in any of the DWARF debug
           information sections.  The 64-bit DWARF format allows larger debug
           information and might not be well supported by all consumers yet.

       -gdescribe-dies
           Add description attributes to some DWARF DIEs that have no name
           attribute, such as artificial variables, external references and call
           site parameter DIEs.

       -gpubnames
           Generate DWARF ".debug_pubnames" and ".debug_pubtypes" sections.

       -ggnu-pubnames
           Generate ".debug_pubnames" and ".debug_pubtypes" sections in a format
           suitable for conversion into a GDB index.  This option is only useful
           with a linker that can produce GDB index version 7.

       -fdebug-types-section
           When using DWARF Version 4 or higher, type DIEs can be put into their
           own ".debug_types" section instead of making them part of the
           ".debug_info" section.  It is more efficient to put them in a
           separate comdat section since the linker can then remove duplicates.
           But not all DWARF consumers support ".debug_types" sections yet and
           on some objects ".debug_types" produces larger instead of smaller
           debugging information.

       -grecord-gcc-switches
       -gno-record-gcc-switches
           This switch causes the command-line options used to invoke the
           compiler that may affect code generation to be appended to the
           DW_AT_producer attribute in DWARF debugging information.  The options
           are concatenated with spaces separating them from each other and from
           the compiler version.  It is enabled by default.  See also
           -frecord-gcc-switches for another way of storing compiler options
           into the object file.

       -gstrict-dwarf
           Disallow using extensions of later DWARF standard version than
           selected with -gdwarf-version.  On most targets using non-conflicting
           DWARF extensions from later standard versions is allowed.

       -gno-strict-dwarf
           Allow using extensions of later DWARF standard version than selected
           with -gdwarf-version.

       -gas-loc-support
           Inform the compiler that the assembler supports ".loc" directives.
           It may then use them for the assembler to generate DWARF2+ line
           number tables.

           This is generally desirable, because assembler-generated line-number
           tables are a lot more compact than those the compiler can generate
           itself.

           This option will be enabled by default if, at GCC configure time, the
           assembler was found to support such directives.

       -gno-as-loc-support
           Force GCC to generate DWARF2+ line number tables internally, if
           DWARF2+ line number tables are to be generated.

       -gas-locview-support
           Inform the compiler that the assembler supports "view" assignment and
           reset assertion checking in ".loc" directives.

           This option will be enabled by default if, at GCC configure time, the
           assembler was found to support them.

       -gno-as-locview-support
           Force GCC to assign view numbers internally, if
           -gvariable-location-views are explicitly requested.

       -gcolumn-info
       -gno-column-info
           Emit location column information into DWARF debugging information,
           rather than just file and line.  This option is enabled by default.

       -gstatement-frontiers
       -gno-statement-frontiers
           This option causes GCC to create markers in the internal
           representation at the beginning of statements, and to keep them
           roughly in place throughout compilation, using them to guide the
           output of "is_stmt" markers in the line number table.  This is
           enabled by default when compiling with optimization (-Os, -O, -O2,
           ...), and outputting DWARF 2 debug information at the normal level.

       -gvariable-location-views
       -gvariable-location-views=incompat5
       -gno-variable-location-views
           Augment variable location lists with progressive view numbers implied
           from the line number table.  This enables debug information consumers
           to inspect state at certain points of the program, even if no
           instructions associated with the corresponding source locations are
           present at that point.  If the assembler lacks support for view
           numbers in line number tables, this will cause the compiler to emit
           the line number table, which generally makes them somewhat less
           compact.  The augmented line number tables and location lists are
           fully backward-compatible, so they can be consumed by debug
           information consumers that are not aware of these augmentations, but
           they won't derive any benefit from them either.

           This is enabled by default when outputting DWARF 2 debug information
           at the normal level, as long as there is assembler support,
           -fvar-tracking-assignments is enabled and -gstrict-dwarf is not.
           When assembler support is not available, this may still be enabled,
           but it will force GCC to output internal line number tables, and if
           -ginternal-reset-location-views is not enabled, that will most
           certainly lead to silently mismatching location views.

           There is a proposed representation for view numbers that is not
           backward compatible with the location list format introduced in DWARF
           5, that can be enabled with -gvariable-location-views=incompat5.
           This option may be removed in the future, is only provided as a
           reference implementation of the proposed representation.  Debug
           information consumers are not expected to support this extended
           format, and they would be rendered unable to decode location lists
           using it.

       -ginternal-reset-location-views
       -gno-internal-reset-location-views
           Attempt to determine location views that can be omitted from location
           view lists.  This requires the compiler to have very accurate insn
           length estimates, which isn't always the case, and it may cause
           incorrect view lists to be generated silently when using an assembler
           that does not support location view lists.  The GNU assembler will
           flag any such error as a "view number mismatch".  This is only
           enabled on ports that define a reliable estimation function.

       -ginline-points
       -gno-inline-points
           Generate extended debug information for inlined functions.  Location
           view tracking markers are inserted at inlined entry points, so that
           address and view numbers can be computed and output in debug
           information.  This can be enabled independently of location views, in
           which case the view numbers won't be output, but it can only be
           enabled along with statement frontiers, and it is only enabled by
           default if location views are enabled.

       -gz[=type]
           Produce compressed debug sections in DWARF format, if that is
           supported.  If type is not given, the default type depends on the
           capabilities of the assembler and linker used.  type may be one of
           none (don't compress debug sections), zlib (use zlib compression in
           ELF gABI format), or zlib-gnu (use zlib compression in traditional
           GNU format).  If the linker doesn't support writing compressed debug
           sections, the option is rejected.  Otherwise, if the assembler does
           not support them, -gz is silently ignored when producing object
           files.

       -femit-struct-debug-baseonly
           Emit debug information for struct-like types only when the base name
           of the compilation source file matches the base name of file in which
           the struct is defined.

           This option substantially reduces the size of debugging information,
           but at significant potential loss in type information to the
           debugger.  See -femit-struct-debug-reduced for a less aggressive
           option.  See -femit-struct-debug-detailed for more detailed control.

           This option works only with DWARF debug output.

       -femit-struct-debug-reduced
           Emit debug information for struct-like types only when the base name
           of the compilation source file matches the base name of file in which
           the type is defined, unless the struct is a template or defined in a
           system header.

           This option significantly reduces the size of debugging information,
           with some potential loss in type information to the debugger.  See
           -femit-struct-debug-baseonly for a more aggressive option.  See
           -femit-struct-debug-detailed for more detailed control.

           This option works only with DWARF debug output.

       -femit-struct-debug-detailed[=spec-list]
           Specify the struct-like types for which the compiler generates debug
           information.  The intent is to reduce duplicate struct debug
           information between different object files within the same program.

           This option is a detailed version of -femit-struct-debug-reduced and
           -femit-struct-debug-baseonly, which serves for most needs.

           A specification has the
           syntax[dir:|ind:][ord:|gen:](any|sys|base|none)

           The optional first word limits the specification to structs that are
           used directly (dir:) or used indirectly (ind:).  A struct type is
           used directly when it is the type of a variable, member.  Indirect
           uses arise through pointers to structs.  That is, when use of an
           incomplete struct is valid, the use is indirect.  An example is
           struct one direct; struct two * indirect;.

           The optional second word limits the specification to ordinary structs
           (ord:) or generic structs (gen:).  Generic structs are a bit
           complicated to explain.  For C++, these are non-explicit
           specializations of template classes, or non-template classes within
           the above.  Other programming languages have generics, but
           -femit-struct-debug-detailed does not yet implement them.

           The third word specifies the source files for those structs for which
           the compiler should emit debug information.  The values none and any
           have the normal meaning.  The value base means that the base of name
           of the file in which the type declaration appears must match the base
           of the name of the main compilation file.  In practice, this means
           that when compiling foo.c, debug information is generated for types
           declared in that file and foo.h, but not other header files.  The
           value sys means those types satisfying base or declared in system or
           compiler headers.

           You may need to experiment to determine the best settings for your
           application.

           The default is -femit-struct-debug-detailed=all.

           This option works only with DWARF debug output.

       -fno-dwarf2-cfi-asm
           Emit DWARF unwind info as compiler generated ".eh_frame" section
           instead of using GAS ".cfi_*" directives.

       -fno-eliminate-unused-debug-types
           Normally, when producing DWARF output, GCC avoids producing debug
           symbol output for types that are nowhere used in the source file
           being compiled.  Sometimes it is useful to have GCC emit debugging
           information for all types declared in a compilation unit, regardless
           of whether or not they are actually used in that compilation unit,
           for example if, in the debugger, you want to cast a value to a type
           that is not actually used in your program (but is declared).  More
           often, however, this results in a significant amount of wasted space.

   Options That Control Optimization
       These options control various sorts of optimizations.

       Without any optimization option, the compiler's goal is to reduce the
       cost of compilation and to make debugging produce the expected results.
       Statements are independent: if you stop the program with a breakpoint
       between statements, you can then assign a new value to any variable or
       change the program counter to any other statement in the function and get
       exactly the results you expect from the source code.

       Turning on optimization flags makes the compiler attempt to improve the
       performance and/or code size at the expense of compilation time and
       possibly the ability to debug the program.

       The compiler performs optimization based on the knowledge it has of the
       program.  Compiling multiple files at once to a single output file mode
       allows the compiler to use information gained from all of the files when
       compiling each of them.

       Not all optimizations are controlled directly by a flag.  Only
       optimizations that have a flag are listed in this section.

       Most optimizations are completely disabled at -O0 or if an -O level is
       not set on the command line, even if individual optimization flags are
       specified.  Similarly, -Og suppresses many optimization passes.

       Depending on the target and how GCC was configured, a slightly different
       set of optimizations may be enabled at each -O level than those listed
       here.  You can invoke GCC with -Q --help=optimizers to find out the exact
       set of optimizations that are enabled at each level.

       -O
       -O1 Optimize.  Optimizing compilation takes somewhat more time, and a lot
           more memory for a large function.

           With -O, the compiler tries to reduce code size and execution time,
           without performing any optimizations that take a great deal of
           compilation time.

           -O turns on the following optimization flags:

           -fauto-inc-dec -fbranch-count-reg -fcombine-stack-adjustments
           -fcompare-elim -fcprop-registers -fdce -fdefer-pop -fdelayed-branch
           -fdse -fforward-propagate -fguess-branch-probability -fif-conversion
           -fif-conversion2 -finline-functions-called-once -fipa-modref
           -fipa-profile -fipa-pure-const -fipa-reference
           -fipa-reference-addressable -fmerge-constants -fmove-loop-invariants
           -fomit-frame-pointer -freorder-blocks -fshrink-wrap
           -fshrink-wrap-separate -fsplit-wide-types -fssa-backprop -fssa-phiopt
           -ftree-bit-ccp -ftree-ccp -ftree-ch -ftree-coalesce-vars
           -ftree-copy-prop -ftree-dce -ftree-dominator-opts -ftree-dse
           -ftree-forwprop -ftree-fre -ftree-phiprop -ftree-pta
           -ftree-scev-cprop -ftree-sink -ftree-slsr -ftree-sra -ftree-ter
           -funit-at-a-time

       -O2 Optimize even more.  GCC performs nearly all supported optimizations
           that do not involve a space-speed tradeoff.  As compared to -O, this
           option increases both compilation time and the performance of the
           generated code.

           -O2 turns on all optimization flags specified by -O.  It also turns
           on the following optimization flags:

           -falign-functions  -falign-jumps -falign-labels  -falign-loops
           -fcaller-saves -fcode-hoisting -fcrossjumping -fcse-follow-jumps
           -fcse-skip-blocks -fdelete-null-pointer-checks -fdevirtualize
           -fdevirtualize-speculatively -fexpensive-optimizations -ffinite-loops
           -fgcse  -fgcse-lm -fhoist-adjacent-loads -finline-functions
           -finline-small-functions -findirect-inlining -fipa-bit-cp  -fipa-cp
           -fipa-icf -fipa-ra  -fipa-sra  -fipa-vrp
           -fisolate-erroneous-paths-dereference -flra-remat
           -foptimize-sibling-calls -foptimize-strlen -fpartial-inlining
           -fpeephole2 -freorder-blocks-algorithm=stc
           -freorder-blocks-and-partition  -freorder-functions
           -frerun-cse-after-loop -fschedule-insns  -fschedule-insns2
           -fsched-interblock  -fsched-spec -fstore-merging -fstrict-aliasing
           -fthread-jumps -ftree-builtin-call-dce -ftree-pre
           -ftree-switch-conversion  -ftree-tail-merge -ftree-vrp

           Please note the warning under -fgcse about invoking -O2 on programs
           that use computed gotos.

       -O3 Optimize yet more.  -O3 turns on all optimizations specified by -O2
           and also turns on the following optimization flags:

           -fgcse-after-reload -fipa-cp-clone -floop-interchange
           -floop-unroll-and-jam -fpeel-loops -fpredictive-commoning
           -fsplit-loops -fsplit-paths -ftree-loop-distribution
           -ftree-loop-vectorize -ftree-partial-pre -ftree-slp-vectorize
           -funswitch-loops -fvect-cost-model -fvect-cost-model=dynamic
           -fversion-loops-for-strides

       -O0 Reduce compilation time and make debugging produce the expected
           results.  This is the default.

       -Os Optimize for size.  -Os enables all -O2 optimizations except those
           that often increase code size:

           -falign-functions  -falign-jumps -falign-labels  -falign-loops
           -fprefetch-loop-arrays  -freorder-blocks-algorithm=stc

           It also enables -finline-functions, causes the compiler to tune for
           code size rather than execution speed, and performs further
           optimizations designed to reduce code size.

       -Ofast
           Disregard strict standards compliance.  -Ofast enables all -O3
           optimizations.  It also enables optimizations that are not valid for
           all standard-compliant programs.  It turns on -ffast-math,
           -fallow-store-data-races and the Fortran-specific -fstack-arrays,
           unless -fmax-stack-var-size is specified, and -fno-protect-parens.

       -Og Optimize debugging experience.  -Og should be the optimization level
           of choice for the standard edit-compile-debug cycle, offering a
           reasonable level of optimization while maintaining fast compilation
           and a good debugging experience.  It is a better choice than -O0 for
           producing debuggable code because some compiler passes that collect
           debug information are disabled at -O0.

           Like -O0, -Og completely disables a number of optimization passes so
           that individual options controlling them have no effect.  Otherwise
           -Og enables all -O1 optimization flags except for those that may
           interfere with debugging:

           -fbranch-count-reg  -fdelayed-branch -fdse  -fif-conversion
           -fif-conversion2 -finline-functions-called-once
           -fmove-loop-invariants  -fssa-phiopt -ftree-bit-ccp  -ftree-dse
           -ftree-pta  -ftree-sra

       If you use multiple -O options, with or without level numbers, the last
       such option is the one that is effective.

       Options of the form -fflag specify machine-independent flags.  Most flags
       have both positive and negative forms; the negative form of -ffoo is
       -fno-foo.  In the table below, only one of the forms is listed---the one
       you typically use.  You can figure out the other form by either removing
       no- or adding it.

       The following options control specific optimizations.  They are either
       activated by -O options or are related to ones that are.  You can use the
       following flags in the rare cases when "fine-tuning" of optimizations to
       be performed is desired.

       -fno-defer-pop
           For machines that must pop arguments after a function call, always
           pop the arguments as soon as each function returns.  At levels -O1
           and higher, -fdefer-pop is the default; this allows the compiler to
           let arguments accumulate on the stack for several function calls and
           pop them all at once.

       -fforward-propagate
           Perform a forward propagation pass on RTL.  The pass tries to combine
           two instructions and checks if the result can be simplified.  If loop
           unrolling is active, two passes are performed and the second is
           scheduled after loop unrolling.

           This option is enabled by default at optimization levels -O, -O2,
           -O3, -Os.

       -ffp-contract=style
           -ffp-contract=off disables floating-point expression contraction.
           -ffp-contract=fast enables floating-point expression contraction such
           as forming of fused multiply-add operations if the target has native
           support for them.  -ffp-contract=on enables floating-point expression
           contraction if allowed by the language standard.  This is currently
           not implemented and treated equal to -ffp-contract=off.

           The default is -ffp-contract=fast.

       -fomit-frame-pointer
           Omit the frame pointer in functions that don't need one.  This avoids
           the instructions to save, set up and restore the frame pointer; on
           many targets it also makes an extra register available.

           On some targets this flag has no effect because the standard calling
           sequence always uses a frame pointer, so it cannot be omitted.

           Note that -fno-omit-frame-pointer doesn't guarantee the frame pointer
           is used in all functions.  Several targets always omit the frame
           pointer in leaf functions.

           Enabled by default at -O and higher.

       -foptimize-sibling-calls
           Optimize sibling and tail recursive calls.

           Enabled at levels -O2, -O3, -Os.

       -foptimize-strlen
           Optimize various standard C string functions (e.g. "strlen", "strchr"
           or "strcpy") and their "_FORTIFY_SOURCE" counterparts into faster
           alternatives.

           Enabled at levels -O2, -O3.

       -fno-inline
           Do not expand any functions inline apart from those marked with the
           "always_inline" attribute.  This is the default when not optimizing.

           Single functions can be exempted from inlining by marking them with
           the "noinline" attribute.

       -finline-small-functions
           Integrate functions into their callers when their body is smaller
           than expected function call code (so overall size of program gets
           smaller).  The compiler heuristically decides which functions are
           simple enough to be worth integrating in this way.  This inlining
           applies to all functions, even those not declared inline.

           Enabled at levels -O2, -O3, -Os.

       -findirect-inlining
           Inline also indirect calls that are discovered to be known at compile
           time thanks to previous inlining.  This option has any effect only
           when inlining itself is turned on by the -finline-functions or
           -finline-small-functions options.

           Enabled at levels -O2, -O3, -Os.

       -finline-functions
           Consider all functions for inlining, even if they are not declared
           inline.  The compiler heuristically decides which functions are worth
           integrating in this way.

           If all calls to a given function are integrated, and the function is
           declared "static", then the function is normally not output as
           assembler code in its own right.

           Enabled at levels -O2, -O3, -Os.  Also enabled by -fprofile-use and
           -fauto-profile.

       -finline-functions-called-once
           Consider all "static" functions called once for inlining into their
           caller even if they are not marked "inline".  If a call to a given
           function is integrated, then the function is not output as assembler
           code in its own right.

           Enabled at levels -O1, -O2, -O3 and -Os, but not -Og.

       -fearly-inlining
           Inline functions marked by "always_inline" and functions whose body
           seems smaller than the function call overhead early before doing
           -fprofile-generate instrumentation and real inlining pass.  Doing so
           makes profiling significantly cheaper and usually inlining faster on
           programs having large chains of nested wrapper functions.

           Enabled by default.

       -fipa-sra
           Perform interprocedural scalar replacement of aggregates, removal of
           unused parameters and replacement of parameters passed by reference
           by parameters passed by value.

           Enabled at levels -O2, -O3 and -Os.

       -finline-limit=n
           By default, GCC limits the size of functions that can be inlined.
           This flag allows coarse control of this limit.  n is the size of
           functions that can be inlined in number of pseudo instructions.

           Inlining is actually controlled by a number of parameters, which may
           be specified individually by using --param name=value.  The
           -finline-limit=n option sets some of these parameters as follows:

           max-inline-insns-single
               is set to n/2.

           max-inline-insns-auto
               is set to n/2.

           See below for a documentation of the individual parameters
           controlling inlining and for the defaults of these parameters.

           Note: there may be no value to -finline-limit that results in default
           behavior.

           Note: pseudo instruction represents, in this particular context, an
           abstract measurement of function's size.  In no way does it represent
           a count of assembly instructions and as such its exact meaning might
           change from one release to an another.

       -fno-keep-inline-dllexport
           This is a more fine-grained version of -fkeep-inline-functions, which
           applies only to functions that are declared using the "dllexport"
           attribute or declspec.

       -fkeep-inline-functions
           In C, emit "static" functions that are declared "inline" into the
           object file, even if the function has been inlined into all of its
           callers.  This switch does not affect functions using the "extern
           inline" extension in GNU C90.  In C++, emit any and all inline
           functions into the object file.

       -fkeep-static-functions
           Emit "static" functions into the object file, even if the function is
           never used.

       -fkeep-static-consts
           Emit variables declared "static const" when optimization isn't turned
           on, even if the variables aren't referenced.

           GCC enables this option by default.  If you want to force the
           compiler to check if a variable is referenced, regardless of whether
           or not optimization is turned on, use the -fno-keep-static-consts
           option.

       -fmerge-constants
           Attempt to merge identical constants (string constants and floating-
           point constants) across compilation units.

           This option is the default for optimized compilation if the assembler
           and linker support it.  Use -fno-merge-constants to inhibit this
           behavior.

           Enabled at levels -O, -O2, -O3, -Os.

       -fmerge-all-constants
           Attempt to merge identical constants and identical variables.

           This option implies -fmerge-constants.  In addition to
           -fmerge-constants this considers e.g. even constant initialized
           arrays or initialized constant variables with integral or floating-
           point types.  Languages like C or C++ require each variable,
           including multiple instances of the same variable in recursive calls,
           to have distinct locations, so using this option results in non-
           conforming behavior.

       -fmodulo-sched
           Perform swing modulo scheduling immediately before the first
           scheduling pass.  This pass looks at innermost loops and reorders
           their instructions by overlapping different iterations.

       -fmodulo-sched-allow-regmoves
           Perform more aggressive SMS-based modulo scheduling with register
           moves allowed.  By setting this flag certain anti-dependences edges
           are deleted, which triggers the generation of reg-moves based on the
           life-range analysis.  This option is effective only with
           -fmodulo-sched enabled.

       -fno-branch-count-reg
           Disable the optimization pass that scans for opportunities to use
           "decrement and branch" instructions on a count register instead of
           instruction sequences that decrement a register, compare it against
           zero, and then branch based upon the result.  This option is only
           meaningful on architectures that support such instructions, which
           include x86, PowerPC, IA-64 and S/390.  Note that the
           -fno-branch-count-reg option doesn't remove the decrement and branch
           instructions from the generated instruction stream introduced by
           other optimization passes.

           The default is -fbranch-count-reg at -O1 and higher, except for -Og.

       -fno-function-cse
           Do not put function addresses in registers; make each instruction
           that calls a constant function contain the function's address
           explicitly.

           This option results in less efficient code, but some strange hacks
           that alter the assembler output may be confused by the optimizations
           performed when this option is not used.

           The default is -ffunction-cse

       -fno-zero-initialized-in-bss
           If the target supports a BSS section, GCC by default puts variables
           that are initialized to zero into BSS.  This can save space in the
           resulting code.

           This option turns off this behavior because some programs explicitly
           rely on variables going to the data section---e.g., so that the
           resulting executable can find the beginning of that section and/or
           make assumptions based on that.

           The default is -fzero-initialized-in-bss.

       -fthread-jumps
           Perform optimizations that check to see if a jump branches to a
           location where another comparison subsumed by the first is found.  If
           so, the first branch is redirected to either the destination of the
           second branch or a point immediately following it, depending on
           whether the condition is known to be true or false.

           Enabled at levels -O2, -O3, -Os.

       -fsplit-wide-types
           When using a type that occupies multiple registers, such as "long
           long" on a 32-bit system, split the registers apart and allocate them
           independently.  This normally generates better code for those types,
           but may make debugging more difficult.

           Enabled at levels -O, -O2, -O3, -Os.

       -fsplit-wide-types-early
           Fully split wide types early, instead of very late.  This option has
           no effect unless -fsplit-wide-types is turned on.

           This is the default on some targets.

       -fcse-follow-jumps
           In common subexpression elimination (CSE), scan through jump
           instructions when the target of the jump is not reached by any other
           path.  For example, when CSE encounters an "if" statement with an
           "else" clause, CSE follows the jump when the condition tested is
           false.

           Enabled at levels -O2, -O3, -Os.

       -fcse-skip-blocks
           This is similar to -fcse-follow-jumps, but causes CSE to follow jumps
           that conditionally skip over blocks.  When CSE encounters a simple
           "if" statement with no else clause, -fcse-skip-blocks causes CSE to
           follow the jump around the body of the "if".

           Enabled at levels -O2, -O3, -Os.

       -frerun-cse-after-loop
           Re-run common subexpression elimination after loop optimizations are
           performed.

           Enabled at levels -O2, -O3, -Os.

       -fgcse
           Perform a global common subexpression elimination pass.  This pass
           also performs global constant and copy propagation.

           Note: When compiling a program using computed gotos, a GCC extension,
           you may get better run-time performance if you disable the global
           common subexpression elimination pass by adding -fno-gcse to the
           command line.

           Enabled at levels -O2, -O3, -Os.

       -fgcse-lm
           When -fgcse-lm is enabled, global common subexpression elimination
           attempts to move loads that are only killed by stores into
           themselves.  This allows a loop containing a load/store sequence to
           be changed to a load outside the loop, and a copy/store within the
           loop.

           Enabled by default when -fgcse is enabled.

       -fgcse-sm
           When -fgcse-sm is enabled, a store motion pass is run after global
           common subexpression elimination.  This pass attempts to move stores
           out of loops.  When used in conjunction with -fgcse-lm, loops
           containing a load/store sequence can be changed to a load before the
           loop and a store after the loop.

           Not enabled at any optimization level.

       -fgcse-las
           When -fgcse-las is enabled, the global common subexpression
           elimination pass eliminates redundant loads that come after stores to
           the same memory location (both partial and full redundancies).

           Not enabled at any optimization level.

       -fgcse-after-reload
           When -fgcse-after-reload is enabled, a redundant load elimination
           pass is performed after reload.  The purpose of this pass is to clean
           up redundant spilling.

           Enabled by -fprofile-use and -fauto-profile.

       -faggressive-loop-optimizations
           This option tells the loop optimizer to use language constraints to
           derive bounds for the number of iterations of a loop.  This assumes
           that loop code does not invoke undefined behavior by for example
           causing signed integer overflows or out-of-bound array accesses.  The
           bounds for the number of iterations of a loop are used to guide loop
           unrolling and peeling and loop exit test optimizations.  This option
           is enabled by default.

       -funconstrained-commons
           This option tells the compiler that variables declared in common
           blocks (e.g. Fortran) may later be overridden with longer trailing
           arrays. This prevents certain optimizations that depend on knowing
           the array bounds.

       -fcrossjumping
           Perform cross-jumping transformation.  This transformation unifies
           equivalent code and saves code size.  The resulting code may or may
           not perform better than without cross-jumping.

           Enabled at levels -O2, -O3, -Os.

       -fauto-inc-dec
           Combine increments or decrements of addresses with memory accesses.
           This pass is always skipped on architectures that do not have
           instructions to support this.  Enabled by default at -O and higher on
           architectures that support this.

       -fdce
           Perform dead code elimination (DCE) on RTL.  Enabled by default at -O
           and higher.

       -fdse
           Perform dead store elimination (DSE) on RTL.  Enabled by default at
           -O and higher.

       -fif-conversion
           Attempt to transform conditional jumps into branch-less equivalents.
           This includes use of conditional moves, min, max, set flags and abs
           instructions, and some tricks doable by standard arithmetics.  The
           use of conditional execution on chips where it is available is
           controlled by -fif-conversion2.

           Enabled at levels -O, -O2, -O3, -Os, but not with -Og.

       -fif-conversion2
           Use conditional execution (where available) to transform conditional
           jumps into branch-less equivalents.

           Enabled at levels -O, -O2, -O3, -Os, but not with -Og.

       -fdeclone-ctor-dtor
           The C++ ABI requires multiple entry points for constructors and
           destructors: one for a base subobject, one for a complete object, and
           one for a virtual destructor that calls operator delete afterwards.
           For a hierarchy with virtual bases, the base and complete variants
           are clones, which means two copies of the function.  With this
           option, the base and complete variants are changed to be thunks that
           call a common implementation.

           Enabled by -Os.

       -fdelete-null-pointer-checks
           Assume that programs cannot safely dereference null pointers, and
           that no code or data element resides at address zero.  This option
           enables simple constant folding optimizations at all optimization
           levels.  In addition, other optimization passes in GCC use this flag
           to control global dataflow analyses that eliminate useless checks for
           null pointers; these assume that a memory access to address zero
           always results in a trap, so that if a pointer is checked after it
           has already been dereferenced, it cannot be null.

           Note however that in some environments this assumption is not true.
           Use -fno-delete-null-pointer-checks to disable this optimization for
           programs that depend on that behavior.

           This option is enabled by default on most targets.  On Nios II ELF,
           it defaults to off.  On AVR, CR16, and MSP430, this option is
           completely disabled.

           Passes that use the dataflow information are enabled independently at
           different optimization levels.

       -fdevirtualize
           Attempt to convert calls to virtual functions to direct calls.  This
           is done both within a procedure and interprocedurally as part of
           indirect inlining (-findirect-inlining) and interprocedural constant
           propagation (-fipa-cp).  Enabled at levels -O2, -O3, -Os.

       -fdevirtualize-speculatively
           Attempt to convert calls to virtual functions to speculative direct
           calls.  Based on the analysis of the type inheritance graph,
           determine for a given call the set of likely targets. If the set is
           small, preferably of size 1, change the call into a conditional
           deciding between direct and indirect calls.  The speculative calls
           enable more optimizations, such as inlining.  When they seem useless
           after further optimization, they are converted back into original
           form.

       -fdevirtualize-at-ltrans
           Stream extra information needed for aggressive devirtualization when
           running the link-time optimizer in local transformation mode.  This
           option enables more devirtualization but significantly increases the
           size of streamed data. For this reason it is disabled by default.

       -fexpensive-optimizations
           Perform a number of minor optimizations that are relatively
           expensive.

           Enabled at levels -O2, -O3, -Os.

       -free
           Attempt to remove redundant extension instructions.  This is
           especially helpful for the x86-64 architecture, which implicitly
           zero-extends in 64-bit registers after writing to their lower 32-bit
           half.

           Enabled for Alpha, AArch64 and x86 at levels -O2, -O3, -Os.

       -fno-lifetime-dse
           In C++ the value of an object is only affected by changes within its
           lifetime: when the constructor begins, the object has an
           indeterminate value, and any changes during the lifetime of the
           object are dead when the object is destroyed.  Normally dead store
           elimination will take advantage of this; if your code relies on the
           value of the object storage persisting beyond the lifetime of the
           object, you can use this flag to disable this optimization.  To
           preserve stores before the constructor starts (e.g. because your
           operator new clears the object storage) but still treat the object as
           dead after the destructor, you can use -flifetime-dse=1.  The default
           behavior can be explicitly selected with -flifetime-dse=2.
           -flifetime-dse=0 is equivalent to -fno-lifetime-dse.

       -flive-range-shrinkage
           Attempt to decrease register pressure through register live range
           shrinkage.  This is helpful for fast processors with small or
           moderate size register sets.

       -fira-algorithm=algorithm
           Use the specified coloring algorithm for the integrated register
           allocator.  The algorithm argument can be priority, which specifies
           Chow's priority coloring, or CB, which specifies Chaitin-Briggs
           coloring.  Chaitin-Briggs coloring is not implemented for all
           architectures, but for those targets that do support it, it is the
           default because it generates better code.

       -fira-region=region
           Use specified regions for the integrated register allocator.  The
           region argument should be one of the following:

           all Use all loops as register allocation regions.  This can give the
               best results for machines with a small and/or irregular register
               set.

           mixed
               Use all loops except for loops with small register pressure as
               the regions.  This value usually gives the best results in most
               cases and for most architectures, and is enabled by default when
               compiling with optimization for speed (-O, -O2, ...).

           one Use all functions as a single region.  This typically results in
               the smallest code size, and is enabled by default for -Os or -O0.

       -fira-hoist-pressure
           Use IRA to evaluate register pressure in the code hoisting pass for
           decisions to hoist expressions.  This option usually results in
           smaller code, but it can slow the compiler down.

           This option is enabled at level -Os for all targets.

       -fira-loop-pressure
           Use IRA to evaluate register pressure in loops for decisions to move
           loop invariants.  This option usually results in generation of faster
           and smaller code on machines with large register files (>= 32
           registers), but it can slow the compiler down.

           This option is enabled at level -O3 for some targets.

       -fno-ira-share-save-slots
           Disable sharing of stack slots used for saving call-used hard
           registers living through a call.  Each hard register gets a separate
           stack slot, and as a result function stack frames are larger.

       -fno-ira-share-spill-slots
           Disable sharing of stack slots allocated for pseudo-registers.  Each
           pseudo-register that does not get a hard register gets a separate
           stack slot, and as a result function stack frames are larger.

       -flra-remat
           Enable CFG-sensitive rematerialization in LRA.  Instead of loading
           values of spilled pseudos, LRA tries to rematerialize (recalculate)
           values if it is profitable.

           Enabled at levels -O2, -O3, -Os.

       -fdelayed-branch
           If supported for the target machine, attempt to reorder instructions
           to exploit instruction slots available after delayed branch
           instructions.

           Enabled at levels -O, -O2, -O3, -Os, but not at -Og.

       -fschedule-insns
           If supported for the target machine, attempt to reorder instructions
           to eliminate execution stalls due to required data being unavailable.
           This helps machines that have slow floating point or memory load
           instructions by allowing other instructions to be issued until the
           result of the load or floating-point instruction is required.

           Enabled at levels -O2, -O3.

       -fschedule-insns2
           Similar to -fschedule-insns, but requests an additional pass of
           instruction scheduling after register allocation has been done.  This
           is especially useful on machines with a relatively small number of
           registers and where memory load instructions take more than one
           cycle.

           Enabled at levels -O2, -O3, -Os.

       -fno-sched-interblock
           Disable instruction scheduling across basic blocks, which is normally
           enabled when scheduling before register allocation, i.e.  with
           -fschedule-insns or at -O2 or higher.

       -fno-sched-spec
           Disable speculative motion of non-load instructions, which is
           normally enabled when scheduling before register allocation, i.e.
           with -fschedule-insns or at -O2 or higher.

       -fsched-pressure
           Enable register pressure sensitive insn scheduling before register
           allocation.  This only makes sense when scheduling before register
           allocation is enabled, i.e. with -fschedule-insns or at -O2 or
           higher.  Usage of this option can improve the generated code and
           decrease its size by preventing register pressure increase above the
           number of available hard registers and subsequent spills in register
           allocation.

       -fsched-spec-load
           Allow speculative motion of some load instructions.  This only makes
           sense when scheduling before register allocation, i.e. with
           -fschedule-insns or at -O2 or higher.

       -fsched-spec-load-dangerous
           Allow speculative motion of more load instructions.  This only makes
           sense when scheduling before register allocation, i.e. with
           -fschedule-insns or at -O2 or higher.

       -fsched-stalled-insns
       -fsched-stalled-insns=n
           Define how many insns (if any) can be moved prematurely from the
           queue of stalled insns into the ready list during the second
           scheduling pass.  -fno-sched-stalled-insns means that no insns are
           moved prematurely, -fsched-stalled-insns=0 means there is no limit on
           how many queued insns can be moved prematurely.
           -fsched-stalled-insns without a value is equivalent to
           -fsched-stalled-insns=1.

       -fsched-stalled-insns-dep
       -fsched-stalled-insns-dep=n
           Define how many insn groups (cycles) are examined for a dependency on
           a stalled insn that is a candidate for premature removal from the
           queue of stalled insns.  This has an effect only during the second
           scheduling pass, and only if -fsched-stalled-insns is used.
           -fno-sched-stalled-insns-dep is equivalent to
           -fsched-stalled-insns-dep=0.  -fsched-stalled-insns-dep without a
           value is equivalent to -fsched-stalled-insns-dep=1.

       -fsched2-use-superblocks
           When scheduling after register allocation, use superblock scheduling.
           This allows motion across basic block boundaries, resulting in faster
           schedules.  This option is experimental, as not all machine
           descriptions used by GCC model the CPU closely enough to avoid
           unreliable results from the algorithm.

           This only makes sense when scheduling after register allocation, i.e.
           with -fschedule-insns2 or at -O2 or higher.

       -fsched-group-heuristic
           Enable the group heuristic in the scheduler.  This heuristic favors
           the instruction that belongs to a schedule group.  This is enabled by
           default when scheduling is enabled, i.e. with -fschedule-insns or
           -fschedule-insns2 or at -O2 or higher.

       -fsched-critical-path-heuristic
           Enable the critical-path heuristic in the scheduler.  This heuristic
           favors instructions on the critical path.  This is enabled by default
           when scheduling is enabled, i.e. with -fschedule-insns or
           -fschedule-insns2 or at -O2 or higher.

       -fsched-spec-insn-heuristic
           Enable the speculative instruction heuristic in the scheduler.  This
           heuristic favors speculative instructions with greater dependency
           weakness.  This is enabled by default when scheduling is enabled,
           i.e.  with -fschedule-insns or -fschedule-insns2 or at -O2 or higher.

       -fsched-rank-heuristic
           Enable the rank heuristic in the scheduler.  This heuristic favors
           the instruction belonging to a basic block with greater size or
           frequency.  This is enabled by default when scheduling is enabled,
           i.e.  with -fschedule-insns or -fschedule-insns2 or at -O2 or higher.

       -fsched-last-insn-heuristic
           Enable the last-instruction heuristic in the scheduler.  This
           heuristic favors the instruction that is less dependent on the last
           instruction scheduled.  This is enabled by default when scheduling is
           enabled, i.e. with -fschedule-insns or -fschedule-insns2 or at -O2 or
           higher.

       -fsched-dep-count-heuristic
           Enable the dependent-count heuristic in the scheduler.  This
           heuristic favors the instruction that has more instructions depending
           on it.  This is enabled by default when scheduling is enabled, i.e.
           with -fschedule-insns or -fschedule-insns2 or at -O2 or higher.

       -freschedule-modulo-scheduled-loops
           Modulo scheduling is performed before traditional scheduling.  If a
           loop is modulo scheduled, later scheduling passes may change its
           schedule.  Use this option to control that behavior.

       -fselective-scheduling
           Schedule instructions using selective scheduling algorithm.
           Selective scheduling runs instead of the first scheduler pass.

       -fselective-scheduling2
           Schedule instructions using selective scheduling algorithm.
           Selective scheduling runs instead of the second scheduler pass.

       -fsel-sched-pipelining
           Enable software pipelining of innermost loops during selective
           scheduling.  This option has no effect unless one of
           -fselective-scheduling or -fselective-scheduling2 is turned on.

       -fsel-sched-pipelining-outer-loops
           When pipelining loops during selective scheduling, also pipeline
           outer loops.  This option has no effect unless -fsel-sched-pipelining
           is turned on.

       -fsemantic-interposition
           Some object formats, like ELF, allow interposing of symbols by the
           dynamic linker.  This means that for symbols exported from the DSO,
           the compiler cannot perform interprocedural propagation, inlining and
           other optimizations in anticipation that the function or variable in
           question may change. While this feature is useful, for example, to
           rewrite memory allocation functions by a debugging implementation, it
           is expensive in the terms of code quality.  With
           -fno-semantic-interposition the compiler assumes that if
           interposition happens for functions the overwriting function will
           have precisely the same semantics (and side effects).  Similarly if
           interposition happens for variables, the constructor of the variable
           will be the same. The flag has no effect for functions explicitly
           declared inline (where it is never allowed for interposition to
           change semantics) and for symbols explicitly declared weak.

       -fshrink-wrap
           Emit function prologues only before parts of the function that need
           it, rather than at the top of the function.  This flag is enabled by
           default at -O and higher.

       -fshrink-wrap-separate
           Shrink-wrap separate parts of the prologue and epilogue separately,
           so that those parts are only executed when needed.  This option is on
           by default, but has no effect unless -fshrink-wrap is also turned on
           and the target supports this.

       -fcaller-saves
           Enable allocation of values to registers that are clobbered by
           function calls, by emitting extra instructions to save and restore
           the registers around such calls.  Such allocation is done only when
           it seems to result in better code.

           This option is always enabled by default on certain machines, usually
           those which have no call-preserved registers to use instead.

           Enabled at levels -O2, -O3, -Os.

       -fcombine-stack-adjustments
           Tracks stack adjustments (pushes and pops) and stack memory
           references and then tries to find ways to combine them.

           Enabled by default at -O1 and higher.

       -fipa-ra
           Use caller save registers for allocation if those registers are not
           used by any called function.  In that case it is not necessary to
           save and restore them around calls.  This is only possible if called
           functions are part of same compilation unit as current function and
           they are compiled before it.

           Enabled at levels -O2, -O3, -Os, however the option is disabled if
           generated code will be instrumented for profiling (-p, or -pg) or if
           callee's register usage cannot be known exactly (this happens on
           targets that do not expose prologues and epilogues in RTL).

       -fconserve-stack
           Attempt to minimize stack usage.  The compiler attempts to use less
           stack space, even if that makes the program slower.  This option
           implies setting the large-stack-frame parameter to 100 and the large-
           stack-frame-growth parameter to 400.

       -ftree-reassoc
           Perform reassociation on trees.  This flag is enabled by default at
           -O and higher.

       -fcode-hoisting
           Perform code hoisting.  Code hoisting tries to move the evaluation of
           expressions executed on all paths to the function exit as early as
           possible.  This is especially useful as a code size optimization, but
           it often helps for code speed as well.  This flag is enabled by
           default at -O2 and higher.

       -ftree-pre
           Perform partial redundancy elimination (PRE) on trees.  This flag is
           enabled by default at -O2 and -O3.

       -ftree-partial-pre
           Make partial redundancy elimination (PRE) more aggressive.  This flag
           is enabled by default at -O3.

       -ftree-forwprop
           Perform forward propagation on trees.  This flag is enabled by
           default at -O and higher.

       -ftree-fre
           Perform full redundancy elimination (FRE) on trees.  The difference
           between FRE and PRE is that FRE only considers expressions that are
           computed on all paths leading to the redundant computation.  This
           analysis is faster than PRE, though it exposes fewer redundancies.
           This flag is enabled by default at -O and higher.

       -ftree-phiprop
           Perform hoisting of loads from conditional pointers on trees.  This
           pass is enabled by default at -O and higher.

       -fhoist-adjacent-loads
           Speculatively hoist loads from both branches of an if-then-else if
           the loads are from adjacent locations in the same structure and the
           target architecture has a conditional move instruction.  This flag is
           enabled by default at -O2 and higher.

       -ftree-copy-prop
           Perform copy propagation on trees.  This pass eliminates unnecessary
           copy operations.  This flag is enabled by default at -O and higher.

       -fipa-pure-const
           Discover which functions are pure or constant.  Enabled by default at
           -O and higher.

       -fipa-reference
           Discover which static variables do not escape the compilation unit.
           Enabled by default at -O and higher.

       -fipa-reference-addressable
           Discover read-only, write-only and non-addressable static variables.
           Enabled by default at -O and higher.

       -fipa-stack-alignment
           Reduce stack alignment on call sites if possible.  Enabled by
           default.

       -fipa-pta
           Perform interprocedural pointer analysis and interprocedural
           modification and reference analysis.  This option can cause excessive
           memory and compile-time usage on large compilation units.  It is not
           enabled by default at any optimization level.

       -fipa-profile
           Perform interprocedural profile propagation.  The functions called
           only from cold functions are marked as cold. Also functions executed
           once (such as "cold", "noreturn", static constructors or destructors)
           are identified. Cold functions and loop less parts of functions
           executed once are then optimized for size.  Enabled by default at -O
           and higher.

       -fipa-modref
           Perform interprocedural mod/ref analysis.  This optimization analyzes
           the side effects of functions (memory locations that are modified or
           referenced) and enables better optimization across the function call
           boundary.  This flag is enabled by default at -O and higher.

       -fipa-cp
           Perform interprocedural constant propagation.  This optimization
           analyzes the program to determine when values passed to functions are
           constants and then optimizes accordingly.  This optimization can
           substantially increase performance if the application has constants
           passed to functions.  This flag is enabled by default at -O2, -Os and
           -O3.  It is also enabled by -fprofile-use and -fauto-profile.

       -fipa-cp-clone
           Perform function cloning to make interprocedural constant propagation
           stronger.  When enabled, interprocedural constant propagation
           performs function cloning when externally visible function can be
           called with constant arguments.  Because this optimization can create
           multiple copies of functions, it may significantly increase code size
           (see --param ipa-cp-unit-growth=value).  This flag is enabled by
           default at -O3.  It is also enabled by -fprofile-use and
           -fauto-profile.

       -fipa-bit-cp
           When enabled, perform interprocedural bitwise constant propagation.
           This flag is enabled by default at -O2 and by -fprofile-use and
           -fauto-profile.  It requires that -fipa-cp is enabled.

       -fipa-vrp
           When enabled, perform interprocedural propagation of value ranges.
           This flag is enabled by default at -O2. It requires that -fipa-cp is
           enabled.

       -fipa-icf
           Perform Identical Code Folding for functions and read-only variables.
           The optimization reduces code size and may disturb unwind stacks by
           replacing a function by equivalent one with a different name. The
           optimization works more effectively with link-time optimization
           enabled.

           Although the behavior is similar to the Gold Linker's ICF
           optimization, GCC ICF works on different levels and thus the
           optimizations are not same - there are equivalences that are found
           only by GCC and equivalences found only by Gold.

           This flag is enabled by default at -O2 and -Os.

       -flive-patching=level
           Control GCC's optimizations to produce output suitable for live-
           patching.

           If the compiler's optimization uses a function's body or information
           extracted from its body to optimize/change another function, the
           latter is called an impacted function of the former.  If a function
           is patched, its impacted functions should be patched too.

           The impacted functions are determined by the compiler's
           interprocedural optimizations.  For example, a caller is impacted
           when inlining a function into its caller, cloning a function and
           changing its caller to call this new clone, or extracting a
           function's pureness/constness information to optimize its direct or
           indirect callers, etc.

           Usually, the more IPA optimizations enabled, the larger the number of
           impacted functions for each function.  In order to control the number
           of impacted functions and more easily compute the list of impacted
           function, IPA optimizations can be partially enabled at two different
           levels.

           The level argument should be one of the following:

           inline-clone
               Only enable inlining and cloning optimizations, which includes
               inlining, cloning, interprocedural scalar replacement of
               aggregates and partial inlining.  As a result, when patching a
               function, all its callers and its clones' callers are impacted,
               therefore need to be patched as well.

               -flive-patching=inline-clone disables the following optimization
               flags: -fwhole-program  -fipa-pta  -fipa-reference  -fipa-ra
               -fipa-icf  -fipa-icf-functions  -fipa-icf-variables -fipa-bit-cp
               -fipa-vrp  -fipa-pure-const  -fipa-reference-addressable
               -fipa-stack-alignment -fipa-modref

           inline-only-static
               Only enable inlining of static functions.  As a result, when
               patching a static function, all its callers are impacted and so
               need to be patched as well.

               In addition to all the flags that -flive-patching=inline-clone
               disables, -flive-patching=inline-only-static disables the
               following additional optimization flags: -fipa-cp-clone
               -fipa-sra  -fpartial-inlining  -fipa-cp

           When -flive-patching is specified without any value, the default
           value is inline-clone.

           This flag is disabled by default.

           Note that -flive-patching is not supported with link-time
           optimization (-flto).

       -fisolate-erroneous-paths-dereference
           Detect paths that trigger erroneous or undefined behavior due to
           dereferencing a null pointer.  Isolate those paths from the main
           control flow and turn the statement with erroneous or undefined
           behavior into a trap.  This flag is enabled by default at -O2 and
           higher and depends on -fdelete-null-pointer-checks also being
           enabled.

       -fisolate-erroneous-paths-attribute
           Detect paths that trigger erroneous or undefined behavior due to a
           null value being used in a way forbidden by a "returns_nonnull" or
           "nonnull" attribute.  Isolate those paths from the main control flow
           and turn the statement with erroneous or undefined behavior into a
           trap.  This is not currently enabled, but may be enabled by -O2 in
           the future.

       -ftree-sink
           Perform forward store motion on trees.  This flag is enabled by
           default at -O and higher.

       -ftree-bit-ccp
           Perform sparse conditional bit constant propagation on trees and
           propagate pointer alignment information.  This pass only operates on
           local scalar variables and is enabled by default at -O1 and higher,
           except for -Og.  It requires that -ftree-ccp is enabled.

       -ftree-ccp
           Perform sparse conditional constant propagation (CCP) on trees.  This
           pass only operates on local scalar variables and is enabled by
           default at -O and higher.

       -fssa-backprop
           Propagate information about uses of a value up the definition chain
           in order to simplify the definitions.  For example, this pass strips
           sign operations if the sign of a value never matters.  The flag is
           enabled by default at -O and higher.

       -fssa-phiopt
           Perform pattern matching on SSA PHI nodes to optimize conditional
           code.  This pass is enabled by default at -O1 and higher, except for
           -Og.

       -ftree-switch-conversion
           Perform conversion of simple initializations in a switch to
           initializations from a scalar array.  This flag is enabled by default
           at -O2 and higher.

       -ftree-tail-merge
           Look for identical code sequences.  When found, replace one with a
           jump to the other.  This optimization is known as tail merging or
           cross jumping.  This flag is enabled by default at -O2 and higher.
           The compilation time in this pass can be limited using max-tail-
           merge-comparisons parameter and max-tail-merge-iterations parameter.

       -ftree-dce
           Perform dead code elimination (DCE) on trees.  This flag is enabled
           by default at -O and higher.

       -ftree-builtin-call-dce
           Perform conditional dead code elimination (DCE) for calls to built-in
           functions that may set "errno" but are otherwise free of side
           effects.  This flag is enabled by default at -O2 and higher if -Os is
           not also specified.

       -ffinite-loops
           Assume that a loop with an exit will eventually take the exit and not
           loop indefinitely.  This allows the compiler to remove loops that
           otherwise have no side-effects, not considering eventual endless
           looping as such.

           This option is enabled by default at -O2 for C++ with -std=c++11 or
           higher.

       -ftree-dominator-opts
           Perform a variety of simple scalar cleanups (constant/copy
           propagation, redundancy elimination, range propagation and expression
           simplification) based on a dominator tree traversal.  This also
           performs jump threading (to reduce jumps to jumps). This flag is
           enabled by default at -O and higher.

       -ftree-dse
           Perform dead store elimination (DSE) on trees.  A dead store is a
           store into a memory location that is later overwritten by another
           store without any intervening loads.  In this case the earlier store
           can be deleted.  This flag is enabled by default at -O and higher.

       -ftree-ch
           Perform loop header copying on trees.  This is beneficial since it
           increases effectiveness of code motion optimizations.  It also saves
           one jump.  This flag is enabled by default at -O and higher.  It is
           not enabled for -Os, since it usually increases code size.

       -ftree-loop-optimize
           Perform loop optimizations on trees.  This flag is enabled by default
           at -O and higher.

       -ftree-loop-linear
       -floop-strip-mine
       -floop-block
           Perform loop nest optimizations.  Same as -floop-nest-optimize.  To
           use this code transformation, GCC has to be configured with
           --with-isl to enable the Graphite loop transformation infrastructure.

       -fgraphite-identity
           Enable the identity transformation for graphite.  For every SCoP we
           generate the polyhedral representation and transform it back to
           gimple.  Using -fgraphite-identity we can check the costs or benefits
           of the GIMPLE -> GRAPHITE -> GIMPLE transformation.  Some minimal
           optimizations are also performed by the code generator isl, like
           index splitting and dead code elimination in loops.

       -floop-nest-optimize
           Enable the isl based loop nest optimizer.  This is a generic loop
           nest optimizer based on the Pluto optimization algorithms.  It
           calculates a loop structure optimized for data-locality and
           parallelism.  This option is experimental.

       -floop-parallelize-all
           Use the Graphite data dependence analysis to identify loops that can
           be parallelized.  Parallelize all the loops that can be analyzed to
           not contain loop carried dependences without checking that it is
           profitable to parallelize the loops.

       -ftree-coalesce-vars
           While transforming the program out of the SSA representation, attempt
           to reduce copying by coalescing versions of different user-defined
           variables, instead of just compiler temporaries.  This may severely
           limit the ability to debug an optimized program compiled with
           -fno-var-tracking-assignments.  In the negated form, this flag
           prevents SSA coalescing of user variables.  This option is enabled by
           default if optimization is enabled, and it does very little
           otherwise.

       -ftree-loop-if-convert
           Attempt to transform conditional jumps in the innermost loops to
           branch-less equivalents.  The intent is to remove control-flow from
           the innermost loops in order to improve the ability of the
           vectorization pass to handle these loops.  This is enabled by default
           if vectorization is enabled.

       -ftree-loop-distribution
           Perform loop distribution.  This flag can improve cache performance
           on big loop bodies and allow further loop optimizations, like
           parallelization or vectorization, to take place.  For example, the
           loop

                   DO I = 1, N
                     A(I) = B(I) + C
                     D(I) = E(I) * F
                   ENDDO

           is transformed to

                   DO I = 1, N
                      A(I) = B(I) + C
                   ENDDO
                   DO I = 1, N
                      D(I) = E(I) * F
                   ENDDO

           This flag is enabled by default at -O3.  It is also enabled by
           -fprofile-use and -fauto-profile.

       -ftree-loop-distribute-patterns
           Perform loop distribution of patterns that can be code generated with
           calls to a library.  This flag is enabled by default at -O2 and
           higher, and by -fprofile-use and -fauto-profile.

           This pass distributes the initialization loops and generates a call
           to memset zero.  For example, the loop

                   DO I = 1, N
                     A(I) = 0
                     B(I) = A(I) + I
                   ENDDO

           is transformed to

                   DO I = 1, N
                      A(I) = 0
                   ENDDO
                   DO I = 1, N
                      B(I) = A(I) + I
                   ENDDO

           and the initialization loop is transformed into a call to memset
           zero.  This flag is enabled by default at -O3.  It is also enabled by
           -fprofile-use and -fauto-profile.

       -floop-interchange
           Perform loop interchange outside of graphite.  This flag can improve
           cache performance on loop nest and allow further loop optimizations,
           like vectorization, to take place.  For example, the loop

                   for (int i = 0; i < N; i++)
                     for (int j = 0; j < N; j++)
                       for (int k = 0; k < N; k++)
                         c[i][j] = c[i][j] + a[i][k]*b[k][j];

           is transformed to

                   for (int i = 0; i < N; i++)
                     for (int k = 0; k < N; k++)
                       for (int j = 0; j < N; j++)
                         c[i][j] = c[i][j] + a[i][k]*b[k][j];

           This flag is enabled by default at -O3.  It is also enabled by
           -fprofile-use and -fauto-profile.

       -floop-unroll-and-jam
           Apply unroll and jam transformations on feasible loops.  In a loop
           nest this unrolls the outer loop by some factor and fuses the
           resulting multiple inner loops.  This flag is enabled by default at
           -O3.  It is also enabled by -fprofile-use and -fauto-profile.

       -ftree-loop-im
           Perform loop invariant motion on trees.  This pass moves only
           invariants that are hard to handle at RTL level (function calls,
           operations that expand to nontrivial sequences of insns).  With
           -funswitch-loops it also moves operands of conditions that are
           invariant out of the loop, so that we can use just trivial
           invariantness analysis in loop unswitching.  The pass also includes
           store motion.

       -ftree-loop-ivcanon
           Create a canonical counter for number of iterations in loops for
           which determining number of iterations requires complicated analysis.
           Later optimizations then may determine the number easily.  Useful
           especially in connection with unrolling.

       -ftree-scev-cprop
           Perform final value replacement.  If a variable is modified in a loop
           in such a way that its value when exiting the loop can be determined
           using only its initial value and the number of loop iterations,
           replace uses of the final value by such a computation, provided it is
           sufficiently cheap.  This reduces data dependencies and may allow
           further simplifications.  Enabled by default at -O and higher.

       -fivopts
           Perform induction variable optimizations (strength reduction,
           induction variable merging and induction variable elimination) on
           trees.

       -ftree-parallelize-loops=n
           Parallelize loops, i.e., split their iteration space to run in n
           threads.  This is only possible for loops whose iterations are
           independent and can be arbitrarily reordered.  The optimization is
           only profitable on multiprocessor machines, for loops that are CPU-
           intensive, rather than constrained e.g. by memory bandwidth.  This
           option implies -pthread, and thus is only supported on targets that
           have support for -pthread.

       -ftree-pta
           Perform function-local points-to analysis on trees.  This flag is
           enabled by default at -O1 and higher, except for -Og.

       -ftree-sra
           Perform scalar replacement of aggregates.  This pass replaces
           structure references with scalars to prevent committing structures to
           memory too early.  This flag is enabled by default at -O1 and higher,
           except for -Og.

       -fstore-merging
           Perform merging of narrow stores to consecutive memory addresses.
           This pass merges contiguous stores of immediate values narrower than
           a word into fewer wider stores to reduce the number of instructions.
           This is enabled by default at -O2 and higher as well as -Os.

       -ftree-ter
           Perform temporary expression replacement during the SSA->normal
           phase.  Single use/single def temporaries are replaced at their use
           location with their defining expression.  This results in non-GIMPLE
           code, but gives the expanders much more complex trees to work on
           resulting in better RTL generation.  This is enabled by default at -O
           and higher.

       -ftree-slsr
           Perform straight-line strength reduction on trees.  This recognizes
           related expressions involving multiplications and replaces them by
           less expensive calculations when possible.  This is enabled by
           default at -O and higher.

       -ftree-vectorize
           Perform vectorization on trees. This flag enables
           -ftree-loop-vectorize and -ftree-slp-vectorize if not explicitly
           specified.

       -ftree-loop-vectorize
           Perform loop vectorization on trees. This flag is enabled by default
           at -O3 and by -ftree-vectorize, -fprofile-use, and -fauto-profile.

       -ftree-slp-vectorize
           Perform basic block vectorization on trees. This flag is enabled by
           default at -O3 and by -ftree-vectorize, -fprofile-use, and
           -fauto-profile.

       -fvect-cost-model=model
           Alter the cost model used for vectorization.  The model argument
           should be one of unlimited, dynamic, cheap or very-cheap.  With the
           unlimited model the vectorized code-path is assumed to be profitable
           while with the dynamic model a runtime check guards the vectorized
           code-path to enable it only for iteration counts that will likely
           execute faster than when executing the original scalar loop.  The
           cheap model disables vectorization of loops where doing so would be
           cost prohibitive for example due to required runtime checks for data
           dependence or alignment but otherwise is equal to the dynamic model.
           The very-cheap model only allows vectorization if the vector code
           would entirely replace the scalar code that is being vectorized.  For
           example, if each iteration of a vectorized loop would only be able to
           handle exactly four iterations of the scalar loop, the very-cheap
           model would only allow vectorization if the scalar iteration count is
           known to be a multiple of four.

           The default cost model depends on other optimization flags and is
           either dynamic or cheap.

       -fsimd-cost-model=model
           Alter the cost model used for vectorization of loops marked with the
           OpenMP simd directive.  The model argument should be one of
           unlimited, dynamic, cheap.  All values of model have the same meaning
           as described in -fvect-cost-model and by default a cost model defined
           with -fvect-cost-model is used.

       -ftree-vrp
           Perform Value Range Propagation on trees.  This is similar to the
           constant propagation pass, but instead of values, ranges of values
           are propagated.  This allows the optimizers to remove unnecessary
           range checks like array bound checks and null pointer checks.  This
           is enabled by default at -O2 and higher.  Null pointer check
           elimination is only done if -fdelete-null-pointer-checks is enabled.

       -fsplit-paths
           Split paths leading to loop backedges.  This can improve dead code
           elimination and common subexpression elimination.  This is enabled by
           default at -O3 and above.

       -fsplit-ivs-in-unroller
           Enables expression of values of induction variables in later
           iterations of the unrolled loop using the value in the first
           iteration.  This breaks long dependency chains, thus improving
           efficiency of the scheduling passes.

           A combination of -fweb and CSE is often sufficient to obtain the same
           effect.  However, that is not reliable in cases where the loop body
           is more complicated than a single basic block.  It also does not work
           at all on some architectures due to restrictions in the CSE pass.

           This optimization is enabled by default.

       -fvariable-expansion-in-unroller
           With this option, the compiler creates multiple copies of some local
           variables when unrolling a loop, which can result in superior code.

           This optimization is enabled by default for PowerPC targets, but
           disabled by default otherwise.

       -fpartial-inlining
           Inline parts of functions.  This option has any effect only when
           inlining itself is turned on by the -finline-functions or
           -finline-small-functions options.

           Enabled at levels -O2, -O3, -Os.

       -fpredictive-commoning
           Perform predictive commoning optimization, i.e., reusing computations
           (especially memory loads and stores) performed in previous iterations
           of loops.

           This option is enabled at level -O3.  It is also enabled by
           -fprofile-use and -fauto-profile.

       -fprefetch-loop-arrays
           If supported by the target machine, generate instructions to prefetch
           memory to improve the performance of loops that access large arrays.

           This option may generate better or worse code; results are highly
           dependent on the structure of loops within the source code.

           Disabled at level -Os.

       -fno-printf-return-value
           Do not substitute constants for known return value of formatted
           output functions such as "sprintf", "snprintf", "vsprintf", and
           "vsnprintf" (but not "printf" of "fprintf").  This transformation
           allows GCC to optimize or even eliminate branches based on the known
           return value of these functions called with arguments that are either
           constant, or whose values are known to be in a range that makes
           determining the exact return value possible.  For example, when
           -fprintf-return-value is in effect, both the branch and the body of
           the "if" statement (but not the call to "snprint") can be optimized
           away when "i" is a 32-bit or smaller integer because the return value
           is guaranteed to be at most 8.

                   char buf[9];
                   if (snprintf (buf, "%08x", i) >= sizeof buf)
                     ...

           The -fprintf-return-value option relies on other optimizations and
           yields best results with -O2 and above.  It works in tandem with the
           -Wformat-overflow and -Wformat-truncation options.  The
           -fprintf-return-value option is enabled by default.

       -fno-peephole
       -fno-peephole2
           Disable any machine-specific peephole optimizations.  The difference
           between -fno-peephole and -fno-peephole2 is in how they are
           implemented in the compiler; some targets use one, some use the
           other, a few use both.

           -fpeephole is enabled by default.  -fpeephole2 enabled at levels -O2,
           -O3, -Os.

       -fno-guess-branch-probability
           Do not guess branch probabilities using heuristics.

           GCC uses heuristics to guess branch probabilities if they are not
           provided by profiling feedback (-fprofile-arcs).  These heuristics
           are based on the control flow graph.  If some branch probabilities
           are specified by "__builtin_expect", then the heuristics are used to
           guess branch probabilities for the rest of the control flow graph,
           taking the "__builtin_expect" info into account.  The interactions
           between the heuristics and "__builtin_expect" can be complex, and in
           some cases, it may be useful to disable the heuristics so that the
           effects of "__builtin_expect" are easier to understand.

           It is also possible to specify expected probability of the expression
           with "__builtin_expect_with_probability" built-in function.

           The default is -fguess-branch-probability at levels -O, -O2, -O3,
           -Os.

       -freorder-blocks
           Reorder basic blocks in the compiled function in order to reduce
           number of taken branches and improve code locality.

           Enabled at levels -O, -O2, -O3, -Os.

       -freorder-blocks-algorithm=algorithm
           Use the specified algorithm for basic block reordering.  The
           algorithm argument can be simple, which does not increase code size
           (except sometimes due to secondary effects like alignment), or stc,
           the "software trace cache" algorithm, which tries to put all often
           executed code together, minimizing the number of branches executed by
           making extra copies of code.

           The default is simple at levels -O, -Os, and stc at levels -O2, -O3.

       -freorder-blocks-and-partition
           In addition to reordering basic blocks in the compiled function, in
           order to reduce number of taken branches, partitions hot and cold
           basic blocks into separate sections of the assembly and .o files, to
           improve paging and cache locality performance.

           This optimization is automatically turned off in the presence of
           exception handling or unwind tables (on targets using
           setjump/longjump or target specific scheme), for linkonce sections,
           for functions with a user-defined section attribute and on any
           architecture that does not support named sections.  When
           -fsplit-stack is used this option is not enabled by default (to avoid
           linker errors), but may be enabled explicitly (if using a working
           linker).

           Enabled for x86 at levels -O2, -O3, -Os.

       -freorder-functions
           Reorder functions in the object file in order to improve code
           locality.  This is implemented by using special subsections
           ".text.hot" for most frequently executed functions and
           ".text.unlikely" for unlikely executed functions.  Reordering is done
           by the linker so object file format must support named sections and
           linker must place them in a reasonable way.

           This option isn't effective unless you either provide profile
           feedback (see -fprofile-arcs for details) or manually annotate
           functions with "hot" or "cold" attributes.

           Enabled at levels -O2, -O3, -Os.

       -fstrict-aliasing
           Allow the compiler to assume the strictest aliasing rules applicable
           to the language being compiled.  For C (and C++), this activates
           optimizations based on the type of expressions.  In particular, an
           object of one type is assumed never to reside at the same address as
           an object of a different type, unless the types are almost the same.
           For example, an "unsigned int" can alias an "int", but not a "void*"
           or a "double".  A character type may alias any other type.

           Pay special attention to code like this:

                   union a_union {
                     int i;
                     double d;
                   };

                   int f() {
                     union a_union t;
                     t.d = 3.0;
                     return t.i;
                   }

           The practice of reading from a different union member than the one
           most recently written to (called "type-punning") is common.  Even
           with -fstrict-aliasing, type-punning is allowed, provided the memory
           is accessed through the union type.  So, the code above works as
           expected.    However, this code might not:

                   int f() {
                     union a_union t;
                     int* ip;
                     t.d = 3.0;
                     ip = &t.i;
                     return *ip;
                   }

           Similarly, access by taking the address, casting the resulting
           pointer and dereferencing the result has undefined behavior, even if
           the cast uses a union type, e.g.:

                   int f() {
                     double d = 3.0;
                     return ((union a_union *) &d)->i;
                   }

           The -fstrict-aliasing option is enabled at levels -O2, -O3, -Os.

       -falign-functions
       -falign-functions=n
       -falign-functions=n:m
       -falign-functions=n:m:n2
       -falign-functions=n:m:n2:m2
           Align the start of functions to the next power-of-two greater than or
           equal to n, skipping up to m-1 bytes.  This ensures that at least the
           first m bytes of the function can be fetched by the CPU without
           crossing an n-byte alignment boundary.

           If m is not specified, it defaults to n.

           Examples: -falign-functions=32 aligns functions to the next 32-byte
           boundary, -falign-functions=24 aligns to the next 32-byte boundary
           only if this can be done by skipping 23 bytes or less,
           -falign-functions=32:7 aligns to the next 32-byte boundary only if
           this can be done by skipping 6 bytes or less.

           The second pair of n2:m2 values allows you to specify a secondary
           alignment: -falign-functions=64:7:32:3 aligns to the next 64-byte
           boundary if this can be done by skipping 6 bytes or less, otherwise
           aligns to the next 32-byte boundary if this can be done by skipping 2
           bytes or less.  If m2 is not specified, it defaults to n2.

           Some assemblers only support this flag when n is a power of two; in
           that case, it is rounded up.

           -fno-align-functions and -falign-functions=1 are equivalent and mean
           that functions are not aligned.

           If n is not specified or is zero, use a machine-dependent default.
           The maximum allowed n option value is 65536.

           Enabled at levels -O2, -O3.

       -flimit-function-alignment
           If this option is enabled, the compiler tries to avoid unnecessarily
           overaligning functions. It attempts to instruct the assembler to
           align by the amount specified by -falign-functions, but not to skip
           more bytes than the size of the function.

       -falign-labels
       -falign-labels=n
       -falign-labels=n:m
       -falign-labels=n:m:n2
       -falign-labels=n:m:n2:m2
           Align all branch targets to a power-of-two boundary.

           Parameters of this option are analogous to the -falign-functions
           option.  -fno-align-labels and -falign-labels=1 are equivalent and
           mean that labels are not aligned.

           If -falign-loops or -falign-jumps are applicable and are greater than
           this value, then their values are used instead.

           If n is not specified or is zero, use a machine-dependent default
           which is very likely to be 1, meaning no alignment.  The maximum
           allowed n option value is 65536.

           Enabled at levels -O2, -O3.

       -falign-loops
       -falign-loops=n
       -falign-loops=n:m
       -falign-loops=n:m:n2
       -falign-loops=n:m:n2:m2
           Align loops to a power-of-two boundary.  If the loops are executed
           many times, this makes up for any execution of the dummy padding
           instructions.

           If -falign-labels is greater than this value, then its value is used
           instead.

           Parameters of this option are analogous to the -falign-functions
           option.  -fno-align-loops and -falign-loops=1 are equivalent and mean
           that loops are not aligned.  The maximum allowed n option value is
           65536.

           If n is not specified or is zero, use a machine-dependent default.

           Enabled at levels -O2, -O3.

       -falign-jumps
       -falign-jumps=n
       -falign-jumps=n:m
       -falign-jumps=n:m:n2
       -falign-jumps=n:m:n2:m2
           Align branch targets to a power-of-two boundary, for branch targets
           where the targets can only be reached by jumping.  In this case, no
           dummy operations need be executed.

           If -falign-labels is greater than this value, then its value is used
           instead.

           Parameters of this option are analogous to the -falign-functions
           option.  -fno-align-jumps and -falign-jumps=1 are equivalent and mean
           that loops are not aligned.

           If n is not specified or is zero, use a machine-dependent default.
           The maximum allowed n option value is 65536.

           Enabled at levels -O2, -O3.

       -fno-allocation-dce
           Do not remove unused C++ allocations in dead code elimination.

       -fallow-store-data-races
           Allow the compiler to perform optimizations that may introduce new
           data races on stores, without proving that the variable cannot be
           concurrently accessed by other threads.  Does not affect optimization
           of local data.  It is safe to use this option if it is known that
           global data will not be accessed by multiple threads.

           Examples of optimizations enabled by -fallow-store-data-races include
           hoisting or if-conversions that may cause a value that was already in
           memory to be re-written with that same value.  Such re-writing is
           safe in a single threaded context but may be unsafe in a multi-
           threaded context.  Note that on some processors, if-conversions may
           be required in order to enable vectorization.

           Enabled at level -Ofast.

       -funit-at-a-time
           This option is left for compatibility reasons. -funit-at-a-time has
           no effect, while -fno-unit-at-a-time implies -fno-toplevel-reorder
           and -fno-section-anchors.

           Enabled by default.

       -fno-toplevel-reorder
           Do not reorder top-level functions, variables, and "asm" statements.
           Output them in the same order that they appear in the input file.
           When this option is used, unreferenced static variables are not
           removed.  This option is intended to support existing code that
           relies on a particular ordering.  For new code, it is better to use
           attributes when possible.

           -ftoplevel-reorder is the default at -O1 and higher, and also at -O0
           if -fsection-anchors is explicitly requested.  Additionally
           -fno-toplevel-reorder implies -fno-section-anchors.

       -fweb
           Constructs webs as commonly used for register allocation purposes and
           assign each web individual pseudo register.  This allows the register
           allocation pass to operate on pseudos directly, but also strengthens
           several other optimization passes, such as CSE, loop optimizer and
           trivial dead code remover.  It can, however, make debugging
           impossible, since variables no longer stay in a "home register".

           Enabled by default with -funroll-loops.

       -fwhole-program
           Assume that the current compilation unit represents the whole program
           being compiled.  All public functions and variables with the
           exception of "main" and those merged by attribute
           "externally_visible" become static functions and in effect are
           optimized more aggressively by interprocedural optimizers.

           This option should not be used in combination with -flto.  Instead
           relying on a linker plugin should provide safer and more precise
           information.

       -flto[=n]
           This option runs the standard link-time optimizer.  When invoked with
           source code, it generates GIMPLE (one of GCC's internal
           representations) and writes it to special ELF sections in the object
           file.  When the object files are linked together, all the function
           bodies are read from these ELF sections and instantiated as if they
           had been part of the same translation unit.

           To use the link-time optimizer, -flto and optimization options should
           be specified at compile time and during the final link.  It is
           recommended that you compile all the files participating in the same
           link with the same options and also specify those options at link
           time.  For example:

                   gcc -c -O2 -flto foo.c
                   gcc -c -O2 -flto bar.c
                   gcc -o myprog -flto -O2 foo.o bar.o

           The first two invocations to GCC save a bytecode representation of
           GIMPLE into special ELF sections inside foo.o and bar.o.  The final
           invocation reads the GIMPLE bytecode from foo.o and bar.o, merges the
           two files into a single internal image, and compiles the result as
           usual.  Since both foo.o and bar.o are merged into a single image,
           this causes all the interprocedural analyses and optimizations in GCC
           to work across the two files as if they were a single one.  This
           means, for example, that the inliner is able to inline functions in
           bar.o into functions in foo.o and vice-versa.

           Another (simpler) way to enable link-time optimization is:

                   gcc -o myprog -flto -O2 foo.c bar.c

           The above generates bytecode for foo.c and bar.c, merges them
           together into a single GIMPLE representation and optimizes them as
           usual to produce myprog.

           The important thing to keep in mind is that to enable link-time
           optimizations you need to use the GCC driver to perform the link
           step.  GCC automatically performs link-time optimization if any of
           the objects involved were compiled with the -flto command-line
           option.  You can always override the automatic decision to do link-
           time optimization by passing -fno-lto to the link command.

           To make whole program optimization effective, it is necessary to make
           certain whole program assumptions.  The compiler needs to know what
           functions and variables can be accessed by libraries and runtime
           outside of the link-time optimized unit.  When supported by the
           linker, the linker plugin (see -fuse-linker-plugin) passes
           information to the compiler about used and externally visible
           symbols.  When the linker plugin is not available, -fwhole-program
           should be used to allow the compiler to make these assumptions, which
           leads to more aggressive optimization decisions.

           When a file is compiled with -flto without -fuse-linker-plugin, the
           generated object file is larger than a regular object file because it
           contains GIMPLE bytecodes and the usual final code (see
           -ffat-lto-objects).  This means that object files with LTO
           information can be linked as normal object files; if -fno-lto is
           passed to the linker, no interprocedural optimizations are applied.
           Note that when -fno-fat-lto-objects is enabled the compile stage is
           faster but you cannot perform a regular, non-LTO link on them.

           When producing the final binary, GCC only applies link-time
           optimizations to those files that contain bytecode.  Therefore, you
           can mix and match object files and libraries with GIMPLE bytecodes
           and final object code.  GCC automatically selects which files to
           optimize in LTO mode and which files to link without further
           processing.

           Generally, options specified at link time override those specified at
           compile time, although in some cases GCC attempts to infer link-time
           options from the settings used to compile the input files.

           If you do not specify an optimization level option -O at link time,
           then GCC uses the highest optimization level used when compiling the
           object files.  Note that it is generally ineffective to specify an
           optimization level option only at link time and not at compile time,
           for two reasons.  First, compiling without optimization suppresses
           compiler passes that gather information needed for effective
           optimization at link time.  Second, some early optimization passes
           can be performed only at compile time and not at link time.

           There are some code generation flags preserved by GCC when generating
           bytecodes, as they need to be used during the final link.  Currently,
           the following options and their settings are taken from the first
           object file that explicitly specifies them: -fcommon, -fexceptions,
           -fnon-call-exceptions, -fgnu-tm and all the -m target flags.

           The following options -fPIC, -fpic, -fpie and -fPIE are combined
           based on the following scheme:

                   B<-fPIC> + B<-fpic> = B<-fpic>
                   B<-fPIC> + B<-fno-pic> = B<-fno-pic>
                   B<-fpic/-fPIC> + (no option) = (no option)
                   B<-fPIC> + B<-fPIE> = B<-fPIE>
                   B<-fpic> + B<-fPIE> = B<-fpie>
                   B<-fPIC/-fpic> + B<-fpie> = B<-fpie>

           Certain ABI-changing flags are required to match in all compilation
           units, and trying to override this at link time with a conflicting
           value is ignored.  This includes options such as -freg-struct-return
           and -fpcc-struct-return.

           Other options such as -ffp-contract, -fno-strict-overflow, -fwrapv,
           -fno-trapv or -fno-strict-aliasing are passed through to the link
           stage and merged conservatively for conflicting translation units.
           Specifically -fno-strict-overflow, -fwrapv and -fno-trapv take
           precedence; and for example -ffp-contract=off takes precedence over
           -ffp-contract=fast.  You can override them at link time.

           Diagnostic options such as -Wstringop-overflow are passed through to
           the link stage and their setting matches that of the compile-step at
           function granularity.  Note that this matters only for diagnostics
           emitted during optimization.  Note that code transforms such as
           inlining can lead to warnings being enabled or disabled for regions
           if code not consistent with the setting at compile time.

           When you need to pass options to the assembler via -Wa or -Xassembler
           make sure to either compile such translation units with -fno-lto or
           consistently use the same assembler options on all translation units.
           You can alternatively also specify assembler options at LTO link
           time.

           To enable debug info generation you need to supply -g at compile
           time.  If any of the input files at link time were built with debug
           info generation enabled the link will enable debug info generation as
           well.  Any elaborate debug info settings like the dwarf level
           -gdwarf-5 need to be explicitly repeated at the linker command line
           and mixing different settings in different translation units is
           discouraged.

           If LTO encounters objects with C linkage declared with incompatible
           types in separate translation units to be linked together (undefined
           behavior according to ISO C99 6.2.7), a non-fatal diagnostic may be
           issued.  The behavior is still undefined at run time.  Similar
           diagnostics may be raised for other languages.

           Another feature of LTO is that it is possible to apply
           interprocedural optimizations on files written in different
           languages:

                   gcc -c -flto foo.c
                   g++ -c -flto bar.cc
                   gfortran -c -flto baz.f90
                   g++ -o myprog -flto -O3 foo.o bar.o baz.o -lgfortran

           Notice that the final link is done with g++ to get the C++ runtime
           libraries and -lgfortran is added to get the Fortran runtime
           libraries.  In general, when mixing languages in LTO mode, you should
           use the same link command options as when mixing languages in a
           regular (non-LTO) compilation.

           If object files containing GIMPLE bytecode are stored in a library
           archive, say libfoo.a, it is possible to extract and use them in an
           LTO link if you are using a linker with plugin support.  To create
           static libraries suitable for LTO, use gcc-ar and gcc-ranlib instead
           of ar and ranlib; to show the symbols of object files with GIMPLE
           bytecode, use gcc-nm.  Those commands require that ar, ranlib and nm
           have been compiled with plugin support.  At link time, use the flag
           -fuse-linker-plugin to ensure that the library participates in the
           LTO optimization process:

                   gcc -o myprog -O2 -flto -fuse-linker-plugin a.o b.o -lfoo

           With the linker plugin enabled, the linker extracts the needed GIMPLE
           files from libfoo.a and passes them on to the running GCC to make
           them part of the aggregated GIMPLE image to be optimized.

           If you are not using a linker with plugin support and/or do not
           enable the linker plugin, then the objects inside libfoo.a are
           extracted and linked as usual, but they do not participate in the LTO
           optimization process.  In order to make a static library suitable for
           both LTO optimization and usual linkage, compile its object files
           with -flto -ffat-lto-objects.

           Link-time optimizations do not require the presence of the whole
           program to operate.  If the program does not require any symbols to
           be exported, it is possible to combine -flto and -fwhole-program to
           allow the interprocedural optimizers to use more aggressive
           assumptions which may lead to improved optimization opportunities.
           Use of -fwhole-program is not needed when linker plugin is active
           (see -fuse-linker-plugin).

           The current implementation of LTO makes no attempt to generate
           bytecode that is portable between different types of hosts.  The
           bytecode files are versioned and there is a strict version check, so
           bytecode files generated in one version of GCC do not work with an
           older or newer version of GCC.

           Link-time optimization does not work well with generation of
           debugging information on systems other than those using a combination
           of ELF and DWARF.

           If you specify the optional n, the optimization and code generation
           done at link time is executed in parallel using n parallel jobs by
           utilizing an installed make program.  The environment variable MAKE
           may be used to override the program used.

           You can also specify -flto=jobserver to use GNU make's job server
           mode to determine the number of parallel jobs. This is useful when
           the Makefile calling GCC is already executing in parallel.  You must
           prepend a + to the command recipe in the parent Makefile for this to
           work.  This option likely only works if MAKE is GNU make.  Even
           without the option value, GCC tries to automatically detect a running
           GNU make's job server.

           Use -flto=auto to use GNU make's job server, if available, or
           otherwise fall back to autodetection of the number of CPU threads
           present in your system.

       -flto-partition=alg
           Specify the partitioning algorithm used by the link-time optimizer.
           The value is either 1to1 to specify a partitioning mirroring the
           original source files or balanced to specify partitioning into
           equally sized chunks (whenever possible) or max to create new
           partition for every symbol where possible.  Specifying none as an
           algorithm disables partitioning and streaming completely.  The
           default value is balanced. While 1to1 can be used as an workaround
           for various code ordering issues, the max partitioning is intended
           for internal testing only.  The value one specifies that exactly one
           partition should be used while the value none bypasses partitioning
           and executes the link-time optimization step directly from the WPA
           phase.

       -flto-compression-level=n
           This option specifies the level of compression used for intermediate
           language written to LTO object files, and is only meaningful in
           conjunction with LTO mode (-flto).  GCC currently supports two LTO
           compression algorithms. For zstd, valid values are 0 (no compression)
           to 19 (maximum compression), while zlib supports values from 0 to 9.
           Values outside this range are clamped to either minimum or maximum of
           the supported values.  If the option is not given, a default balanced
           compression setting is used.

       -fuse-linker-plugin
           Enables the use of a linker plugin during link-time optimization.
           This option relies on plugin support in the linker, which is
           available in gold or in GNU ld 2.21 or newer.

           This option enables the extraction of object files with GIMPLE
           bytecode out of library archives. This improves the quality of
           optimization by exposing more code to the link-time optimizer.  This
           information specifies what symbols can be accessed externally (by
           non-LTO object or during dynamic linking).  Resulting code quality
           improvements on binaries (and shared libraries that use hidden
           visibility) are similar to -fwhole-program.  See -flto for a
           description of the effect of this flag and how to use it.

           This option is enabled by default when LTO support in GCC is enabled
           and GCC was configured for use with a linker supporting plugins (GNU
           ld 2.21 or newer or gold).

       -ffat-lto-objects
           Fat LTO objects are object files that contain both the intermediate
           language and the object code. This makes them usable for both LTO
           linking and normal linking. This option is effective only when
           compiling with -flto and is ignored at link time.

           -fno-fat-lto-objects improves compilation time over plain LTO, but
           requires the complete toolchain to be aware of LTO. It requires a
           linker with linker plugin support for basic functionality.
           Additionally, nm, ar and ranlib need to support linker plugins to
           allow a full-featured build environment (capable of building static
           libraries etc).  GCC provides the gcc-ar, gcc-nm, gcc-ranlib wrappers
           to pass the right options to these tools. With non fat LTO makefiles
           need to be modified to use them.

           Note that modern binutils provide plugin auto-load mechanism.
           Installing the linker plugin into $libdir/bfd-plugins has the same
           effect as usage of the command wrappers (gcc-ar, gcc-nm and gcc-
           ranlib).

           The default is -fno-fat-lto-objects on targets with linker plugin
           support.

       -fcompare-elim
           After register allocation and post-register allocation instruction
           splitting, identify arithmetic instructions that compute processor
           flags similar to a comparison operation based on that arithmetic.  If
           possible, eliminate the explicit comparison operation.

           This pass only applies to certain targets that cannot explicitly
           represent the comparison operation before register allocation is
           complete.

           Enabled at levels -O, -O2, -O3, -Os.

       -fcprop-registers
           After register allocation and post-register allocation instruction
           splitting, perform a copy-propagation pass to try to reduce
           scheduling dependencies and occasionally eliminate the copy.

           Enabled at levels -O, -O2, -O3, -Os.

       -fprofile-correction
           Profiles collected using an instrumented binary for multi-threaded
           programs may be inconsistent due to missed counter updates. When this
           option is specified, GCC uses heuristics to correct or smooth out
           such inconsistencies. By default, GCC emits an error message when an
           inconsistent profile is detected.

           This option is enabled by -fauto-profile.

       -fprofile-partial-training
           With "-fprofile-use" all portions of programs not executed during
           train run are optimized agressively for size rather than speed.  In
           some cases it is not practical to train all possible hot paths in the
           program. (For example, program may contain functions specific for a
           given hardware and trianing may not cover all hardware configurations
           program is run on.)  With "-fprofile-partial-training" profile
           feedback will be ignored for all functions not executed during the
           train run leading them to be optimized as if they were compiled
           without profile feedback. This leads to better performance when train
           run is not representative but also leads to significantly bigger
           code.

       -fprofile-use
       -fprofile-use=path
           Enable profile feedback-directed optimizations, and the following
           optimizations, many of which are generally profitable only with
           profile feedback available:

           -fbranch-probabilities  -fprofile-values -funroll-loops  -fpeel-loops
           -ftracer  -fvpt -finline-functions  -fipa-cp  -fipa-cp-clone
           -fipa-bit-cp -fpredictive-commoning  -fsplit-loops  -funswitch-loops
           -fgcse-after-reload  -ftree-loop-vectorize  -ftree-slp-vectorize
           -fvect-cost-model=dynamic  -ftree-loop-distribute-patterns
           -fprofile-reorder-functions

           Before you can use this option, you must first generate profiling
           information.

           By default, GCC emits an error message if the feedback profiles do
           not match the source code.  This error can be turned into a warning
           by using -Wno-error=coverage-mismatch.  Note this may result in
           poorly optimized code.  Additionally, by default, GCC also emits a
           warning message if the feedback profiles do not exist (see
           -Wmissing-profile).

           If path is specified, GCC looks at the path to find the profile
           feedback data files. See -fprofile-dir.

       -fauto-profile
       -fauto-profile=path
           Enable sampling-based feedback-directed optimizations, and the
           following optimizations, many of which are generally profitable only
           with profile feedback available:

           -fbranch-probabilities  -fprofile-values -funroll-loops  -fpeel-loops
           -ftracer  -fvpt -finline-functions  -fipa-cp  -fipa-cp-clone
           -fipa-bit-cp -fpredictive-commoning  -fsplit-loops  -funswitch-loops
           -fgcse-after-reload  -ftree-loop-vectorize  -ftree-slp-vectorize
           -fvect-cost-model=dynamic  -ftree-loop-distribute-patterns
           -fprofile-correction

           path is the name of a file containing AutoFDO profile information.
           If omitted, it defaults to fbdata.afdo in the current directory.

           Producing an AutoFDO profile data file requires running your program
           with the perf utility on a supported GNU/Linux target system.  For
           more information, see <https://perf.wiki.kernel.org/>.

           E.g.

                   perf record -e br_inst_retired:near_taken -b -o perf.data \
                       -- your_program

           Then use the create_gcov tool to convert the raw profile data to a
           format that can be used by GCC.  You must also supply the unstripped
           binary for your program to this tool.  See
           <https://github.com/google/autofdo>.

           E.g.

                   create_gcov --binary=your_program.unstripped --profile=perf.data \
                       --gcov=profile.afdo

       The following options control compiler behavior regarding floating-point
       arithmetic.  These options trade off between speed and correctness.  All
       must be specifically enabled.

       -ffloat-store
           Do not store floating-point variables in registers, and inhibit other
           options that might change whether a floating-point value is taken
           from a register or memory.

           This option prevents undesirable excess precision on machines such as
           the 68000 where the floating registers (of the 68881) keep more
           precision than a "double" is supposed to have.  Similarly for the x86
           architecture.  For most programs, the excess precision does only
           good, but a few programs rely on the precise definition of IEEE
           floating point.  Use -ffloat-store for such programs, after modifying
           them to store all pertinent intermediate computations into variables.

       -fexcess-precision=style
           This option allows further control over excess precision on machines
           where floating-point operations occur in a format with more precision
           or range than the IEEE standard and interchange floating-point types.
           By default, -fexcess-precision=fast is in effect; this means that
           operations may be carried out in a wider precision than the types
           specified in the source if that would result in faster code, and it
           is unpredictable when rounding to the types specified in the source
           code takes place.  When compiling C, if -fexcess-precision=standard
           is specified then excess precision follows the rules specified in ISO
           C99; in particular, both casts and assignments cause values to be
           rounded to their semantic types (whereas -ffloat-store only affects
           assignments).  This option is enabled by default for C if a strict
           conformance option such as -std=c99 is used.  -ffast-math enables
           -fexcess-precision=fast by default regardless of whether a strict
           conformance option is used.

           -fexcess-precision=standard is not implemented for languages other
           than C.  On the x86, it has no effect if -mfpmath=sse or
           -mfpmath=sse+387 is specified; in the former case, IEEE semantics
           apply without excess precision, and in the latter, rounding is
           unpredictable.

       -ffast-math
           Sets the options -fno-math-errno, -funsafe-math-optimizations,
           -ffinite-math-only, -fno-rounding-math, -fno-signaling-nans,
           -fcx-limited-range and -fexcess-precision=fast.

           This option causes the preprocessor macro "__FAST_MATH__" to be
           defined.

           This option is not turned on by any -O option besides -Ofast since it
           can result in incorrect output for programs that depend on an exact
           implementation of IEEE or ISO rules/specifications for math
           functions. It may, however, yield faster code for programs that do
           not require the guarantees of these specifications.

       -fno-math-errno
           Do not set "errno" after calling math functions that are executed
           with a single instruction, e.g., "sqrt".  A program that relies on
           IEEE exceptions for math error handling may want to use this flag for
           speed while maintaining IEEE arithmetic compatibility.

           This option is not turned on by any -O option since it can result in
           incorrect output for programs that depend on an exact implementation
           of IEEE or ISO rules/specifications for math functions. It may,
           however, yield faster code for programs that do not require the
           guarantees of these specifications.

           The default is -fmath-errno.

           On Darwin systems, the math library never sets "errno".  There is
           therefore no reason for the compiler to consider the possibility that
           it might, and -fno-math-errno is the default.

       -funsafe-math-optimizations
           Allow optimizations for floating-point arithmetic that (a) assume
           that arguments and results are valid and (b) may violate IEEE or ANSI
           standards.  When used at link time, it may include libraries or
           startup files that change the default FPU control word or other
           similar optimizations.

           This option is not turned on by any -O option since it can result in
           incorrect output for programs that depend on an exact implementation
           of IEEE or ISO rules/specifications for math functions. It may,
           however, yield faster code for programs that do not require the
           guarantees of these specifications.  Enables -fno-signed-zeros,
           -fno-trapping-math, -fassociative-math and -freciprocal-math.

           The default is -fno-unsafe-math-optimizations.

       -fassociative-math
           Allow re-association of operands in series of floating-point
           operations.  This violates the ISO C and C++ language standard by
           possibly changing computation result.  NOTE: re-ordering may change
           the sign of zero as well as ignore NaNs and inhibit or create
           underflow or overflow (and thus cannot be used on code that relies on
           rounding behavior like "(x + 2**52) - 2**52".  May also reorder
           floating-point comparisons and thus may not be used when ordered
           comparisons are required.  This option requires that both
           -fno-signed-zeros and -fno-trapping-math be in effect.  Moreover, it
           doesn't make much sense with -frounding-math. For Fortran the option
           is automatically enabled when both -fno-signed-zeros and
           -fno-trapping-math are in effect.

           The default is -fno-associative-math.

       -freciprocal-math
           Allow the reciprocal of a value to be used instead of dividing by the
           value if this enables optimizations.  For example "x / y" can be
           replaced with "x * (1/y)", which is useful if "(1/y)" is subject to
           common subexpression elimination.  Note that this loses precision and
           increases the number of flops operating on the value.

           The default is -fno-reciprocal-math.

       -ffinite-math-only
           Allow optimizations for floating-point arithmetic that assume that
           arguments and results are not NaNs or +-Infs.

           This option is not turned on by any -O option since it can result in
           incorrect output for programs that depend on an exact implementation
           of IEEE or ISO rules/specifications for math functions. It may,
           however, yield faster code for programs that do not require the
           guarantees of these specifications.

           The default is -fno-finite-math-only.

       -fno-signed-zeros
           Allow optimizations for floating-point arithmetic that ignore the
           signedness of zero.  IEEE arithmetic specifies the behavior of
           distinct +0.0 and -0.0 values, which then prohibits simplification of
           expressions such as x+0.0 or 0.0*x (even with -ffinite-math-only).
           This option implies that the sign of a zero result isn't significant.

           The default is -fsigned-zeros.

       -fno-trapping-math
           Compile code assuming that floating-point operations cannot generate
           user-visible traps.  These traps include division by zero, overflow,
           underflow, inexact result and invalid operation.  This option
           requires that -fno-signaling-nans be in effect.  Setting this option
           may allow faster code if one relies on "non-stop" IEEE arithmetic,
           for example.

           This option should never be turned on by any -O option since it can
           result in incorrect output for programs that depend on an exact
           implementation of IEEE or ISO rules/specifications for math
           functions.

           The default is -ftrapping-math.

       -frounding-math
           Disable transformations and optimizations that assume default
           floating-point rounding behavior.  This is round-to-zero for all
           floating point to integer conversions, and round-to-nearest for all
           other arithmetic truncations.  This option should be specified for
           programs that change the FP rounding mode dynamically, or that may be
           executed with a non-default rounding mode.  This option disables
           constant folding of floating-point expressions at compile time (which
           may be affected by rounding mode) and arithmetic transformations that
           are unsafe in the presence of sign-dependent rounding modes.

           The default is -fno-rounding-math.

           This option is experimental and does not currently guarantee to
           disable all GCC optimizations that are affected by rounding mode.
           Future versions of GCC may provide finer control of this setting
           using C99's "FENV_ACCESS" pragma.  This command-line option will be
           used to specify the default state for "FENV_ACCESS".

       -fsignaling-nans
           Compile code assuming that IEEE signaling NaNs may generate user-
           visible traps during floating-point operations.  Setting this option
           disables optimizations that may change the number of exceptions
           visible with signaling NaNs.  This option implies -ftrapping-math.

           This option causes the preprocessor macro "__SUPPORT_SNAN__" to be
           defined.

           The default is -fno-signaling-nans.

           This option is experimental and does not currently guarantee to
           disable all GCC optimizations that affect signaling NaN behavior.

       -fno-fp-int-builtin-inexact
           Do not allow the built-in functions "ceil", "floor", "round" and
           "trunc", and their "float" and "long double" variants, to generate
           code that raises the "inexact" floating-point exception for
           noninteger arguments.  ISO C99 and C11 allow these functions to raise
           the "inexact" exception, but ISO/IEC TS 18661-1:2014, the C bindings
           to IEEE 754-2008, as integrated into ISO C2X, does not allow these
           functions to do so.

           The default is -ffp-int-builtin-inexact, allowing the exception to be
           raised, unless C2X or a later C standard is selected.  This option
           does nothing unless -ftrapping-math is in effect.

           Even if -fno-fp-int-builtin-inexact is used, if the functions
           generate a call to a library function then the "inexact" exception
           may be raised if the library implementation does not follow TS 18661.

       -fsingle-precision-constant
           Treat floating-point constants as single precision instead of
           implicitly converting them to double-precision constants.

       -fcx-limited-range
           When enabled, this option states that a range reduction step is not
           needed when performing complex division.  Also, there is no checking
           whether the result of a complex multiplication or division is "NaN +
           I*NaN", with an attempt to rescue the situation in that case.  The
           default is -fno-cx-limited-range, but is enabled by -ffast-math.

           This option controls the default setting of the ISO C99
           "CX_LIMITED_RANGE" pragma.  Nevertheless, the option applies to all
           languages.

       -fcx-fortran-rules
           Complex multiplication and division follow Fortran rules.  Range
           reduction is done as part of complex division, but there is no
           checking whether the result of a complex multiplication or division
           is "NaN + I*NaN", with an attempt to rescue the situation in that
           case.

           The default is -fno-cx-fortran-rules.

       The following options control optimizations that may improve performance,
       but are not enabled by any -O options.  This section includes
       experimental options that may produce broken code.

       -fbranch-probabilities
           After running a program compiled with -fprofile-arcs, you can compile
           it a second time using -fbranch-probabilities, to improve
           optimizations based on the number of times each branch was taken.
           When a program compiled with -fprofile-arcs exits, it saves arc
           execution counts to a file called sourcename.gcda for each source
           file.  The information in this data file is very dependent on the
           structure of the generated code, so you must use the same source code
           and the same optimization options for both compilations.

           With -fbranch-probabilities, GCC puts a REG_BR_PROB note on each
           JUMP_INSN and CALL_INSN.  These can be used to improve optimization.
           Currently, they are only used in one place: in reorg.c, instead of
           guessing which path a branch is most likely to take, the REG_BR_PROB
           values are used to exactly determine which path is taken more often.

           Enabled by -fprofile-use and -fauto-profile.

       -fprofile-values
           If combined with -fprofile-arcs, it adds code so that some data about
           values of expressions in the program is gathered.

           With -fbranch-probabilities, it reads back the data gathered from
           profiling values of expressions for usage in optimizations.

           Enabled by -fprofile-generate, -fprofile-use, and -fauto-profile.

       -fprofile-reorder-functions
           Function reordering based on profile instrumentation collects first
           time of execution of a function and orders these functions in
           ascending order.

           Enabled with -fprofile-use.

       -fvpt
           If combined with -fprofile-arcs, this option instructs the compiler
           to add code to gather information about values of expressions.

           With -fbranch-probabilities, it reads back the data gathered and
           actually performs the optimizations based on them.  Currently the
           optimizations include specialization of division operations using the
           knowledge about the value of the denominator.

           Enabled with -fprofile-use and -fauto-profile.

       -frename-registers
           Attempt to avoid false dependencies in scheduled code by making use
           of registers left over after register allocation.  This optimization
           most benefits processors with lots of registers.  Depending on the
           debug information format adopted by the target, however, it can make
           debugging impossible, since variables no longer stay in a "home
           register".

           Enabled by default with -funroll-loops.

       -fschedule-fusion
           Performs a target dependent pass over the instruction stream to
           schedule instructions of same type together because target machine
           can execute them more efficiently if they are adjacent to each other
           in the instruction flow.

           Enabled at levels -O2, -O3, -Os.

       -ftracer
           Perform tail duplication to enlarge superblock size.  This
           transformation simplifies the control flow of the function allowing
           other optimizations to do a better job.

           Enabled by -fprofile-use and -fauto-profile.

       -funroll-loops
           Unroll loops whose number of iterations can be determined at compile
           time or upon entry to the loop.  -funroll-loops implies
           -frerun-cse-after-loop, -fweb and -frename-registers.  It also turns
           on complete loop peeling (i.e. complete removal of loops with a small
           constant number of iterations).  This option makes code larger, and
           may or may not make it run faster.

           Enabled by -fprofile-use and -fauto-profile.

       -funroll-all-loops
           Unroll all loops, even if their number of iterations is uncertain
           when the loop is entered.  This usually makes programs run more
           slowly.  -funroll-all-loops implies the same options as
           -funroll-loops.

       -fpeel-loops
           Peels loops for which there is enough information that they do not
           roll much (from profile feedback or static analysis).  It also turns
           on complete loop peeling (i.e. complete removal of loops with small
           constant number of iterations).

           Enabled by -O3, -fprofile-use, and -fauto-profile.

       -fmove-loop-invariants
           Enables the loop invariant motion pass in the RTL loop optimizer.
           Enabled at level -O1 and higher, except for -Og.

       -fsplit-loops
           Split a loop into two if it contains a condition that's always true
           for one side of the iteration space and false for the other.

           Enabled by -fprofile-use and -fauto-profile.

       -funswitch-loops
           Move branches with loop invariant conditions out of the loop, with
           duplicates of the loop on both branches (modified according to result
           of the condition).

           Enabled by -fprofile-use and -fauto-profile.

       -fversion-loops-for-strides
           If a loop iterates over an array with a variable stride, create
           another version of the loop that assumes the stride is always one.
           For example:

                   for (int i = 0; i < n; ++i)
                     x[i * stride] = ...;

           becomes:

                   if (stride == 1)
                     for (int i = 0; i < n; ++i)
                       x[i] = ...;
                   else
                     for (int i = 0; i < n; ++i)
                       x[i * stride] = ...;

           This is particularly useful for assumed-shape arrays in Fortran where
           (for example) it allows better vectorization assuming contiguous
           accesses.  This flag is enabled by default at -O3.  It is also
           enabled by -fprofile-use and -fauto-profile.

       -ffunction-sections
       -fdata-sections
           Place each function or data item into its own section in the output
           file if the target supports arbitrary sections.  The name of the
           function or the name of the data item determines the section's name
           in the output file.

           Use these options on systems where the linker can perform
           optimizations to improve locality of reference in the instruction
           space.  Most systems using the ELF object format have linkers with
           such optimizations.  On AIX, the linker rearranges sections (CSECTs)
           based on the call graph.  The performance impact varies.

           Together with a linker garbage collection (linker --gc-sections
           option) these options may lead to smaller statically-linked
           executables (after stripping).

           On ELF/DWARF systems these options do not degenerate the quality of
           the debug information.  There could be issues with other object
           files/debug info formats.

           Only use these options when there are significant benefits from doing
           so.  When you specify these options, the assembler and linker create
           larger object and executable files and are also slower.  These
           options affect code generation.  They prevent optimizations by the
           compiler and assembler using relative locations inside a translation
           unit since the locations are unknown until link time.  An example of
           such an optimization is relaxing calls to short call instructions.

       -fstdarg-opt
           Optimize the prologue of variadic argument functions with respect to
           usage of those arguments.

       -fsection-anchors
           Try to reduce the number of symbolic address calculations by using
           shared "anchor" symbols to address nearby objects.  This
           transformation can help to reduce the number of GOT entries and GOT
           accesses on some targets.

           For example, the implementation of the following function "foo":

                   static int a, b, c;
                   int foo (void) { return a + b + c; }

           usually calculates the addresses of all three variables, but if you
           compile it with -fsection-anchors, it accesses the variables from a
           common anchor point instead.  The effect is similar to the following
           pseudocode (which isn't valid C):

                   int foo (void)
                   {
                     register int *xr = &x;
                     return xr[&a - &x] + xr[&b - &x] + xr[&c - &x];
                   }

           Not all targets support this option.

       -fzero-call-used-regs=choice
           Zero call-used registers at function return to increase program
           security by either mitigating Return-Oriented Programming (ROP)
           attacks or preventing information leakage through registers.

           The possible values of choice are the same as for the
           "zero_call_used_regs" attribute.  The default is skip.

           You can control this behavior for a specific function by using the
           function attribute "zero_call_used_regs".

       --param name=value
           In some places, GCC uses various constants to control the amount of
           optimization that is done.  For example, GCC does not inline
           functions that contain more than a certain number of instructions.
           You can control some of these constants on the command line using the
           --param option.

           The names of specific parameters, and the meaning of the values, are
           tied to the internals of the compiler, and are subject to change
           without notice in future releases.

           In order to get minimal, maximal and default value of a parameter,
           one can use --help=param -Q options.

           In each case, the value is an integer.  The following choices of name
           are recognized for all targets:

           predictable-branch-outcome
               When branch is predicted to be taken with probability lower than
               this threshold (in percent), then it is considered well
               predictable.

           max-rtl-if-conversion-insns
               RTL if-conversion tries to remove conditional branches around a
               block and replace them with conditionally executed instructions.
               This parameter gives the maximum number of instructions in a
               block which should be considered for if-conversion.  The compiler
               will also use other heuristics to decide whether if-conversion is
               likely to be profitable.

           max-rtl-if-conversion-predictable-cost
               RTL if-conversion will try to remove conditional branches around
               a block and replace them with conditionally executed
               instructions.  These parameters give the maximum permissible cost
               for the sequence that would be generated by if-conversion
               depending on whether the branch is statically determined to be
               predictable or not.  The units for this parameter are the same as
               those for the GCC internal seq_cost metric.  The compiler will
               try to provide a reasonable default for this parameter using the
               BRANCH_COST target macro.

           max-crossjump-edges
               The maximum number of incoming edges to consider for cross-
               jumping.  The algorithm used by -fcrossjumping is O(N^2) in the
               number of edges incoming to each block.  Increasing values mean
               more aggressive optimization, making the compilation time
               increase with probably small improvement in executable size.

           min-crossjump-insns
               The minimum number of instructions that must be matched at the
               end of two blocks before cross-jumping is performed on them.
               This value is ignored in the case where all instructions in the
               block being cross-jumped from are matched.

           max-grow-copy-bb-insns
               The maximum code size expansion factor when copying basic blocks
               instead of jumping.  The expansion is relative to a jump
               instruction.

           max-goto-duplication-insns
               The maximum number of instructions to duplicate to a block that
               jumps to a computed goto.  To avoid O(N^2) behavior in a number
               of passes, GCC factors computed gotos early in the compilation
               process, and unfactors them as late as possible.  Only computed
               jumps at the end of a basic blocks with no more than max-goto-
               duplication-insns are unfactored.

           max-delay-slot-insn-search
               The maximum number of instructions to consider when looking for
               an instruction to fill a delay slot.  If more than this arbitrary
               number of instructions are searched, the time savings from
               filling the delay slot are minimal, so stop searching.
               Increasing values mean more aggressive optimization, making the
               compilation time increase with probably small improvement in
               execution time.

           max-delay-slot-live-search
               When trying to fill delay slots, the maximum number of
               instructions to consider when searching for a block with valid
               live register information.  Increasing this arbitrarily chosen
               value means more aggressive optimization, increasing the
               compilation time.  This parameter should be removed when the
               delay slot code is rewritten to maintain the control-flow graph.

           max-gcse-memory
               The approximate maximum amount of memory in "kB" that can be
               allocated in order to perform the global common subexpression
               elimination optimization.  If more memory than specified is
               required, the optimization is not done.

           max-gcse-insertion-ratio
               If the ratio of expression insertions to deletions is larger than
               this value for any expression, then RTL PRE inserts or removes
               the expression and thus leaves partially redundant computations
               in the instruction stream.

           max-pending-list-length
               The maximum number of pending dependencies scheduling allows
               before flushing the current state and starting over.  Large
               functions with few branches or calls can create excessively large
               lists which needlessly consume memory and resources.

           max-modulo-backtrack-attempts
               The maximum number of backtrack attempts the scheduler should
               make when modulo scheduling a loop.  Larger values can
               exponentially increase compilation time.

           max-inline-insns-single
               Several parameters control the tree inliner used in GCC.  This
               number sets the maximum number of instructions (counted in GCC's
               internal representation) in a single function that the tree
               inliner considers for inlining.  This only affects functions
               declared inline and methods implemented in a class declaration
               (C++).

           max-inline-insns-auto
               When you use -finline-functions (included in -O3), a lot of
               functions that would otherwise not be considered for inlining by
               the compiler are investigated.  To those functions, a different
               (more restrictive) limit compared to functions declared inline
               can be applied (--param max-inline-insns-auto).

           max-inline-insns-small
               This is bound applied to calls which are considered relevant with
               -finline-small-functions.

           max-inline-insns-size
               This is bound applied to calls which are optimized for size.
               Small growth may be desirable to anticipate optimization
               oppurtunities exposed by inlining.

           uninlined-function-insns
               Number of instructions accounted by inliner for function overhead
               such as function prologue and epilogue.

           uninlined-function-time
               Extra time accounted by inliner for function overhead such as
               time needed to execute function prologue and epilogue

           inline-heuristics-hint-percent
               The scale (in percents) applied to inline-insns-single,
               inline-insns-single-O2, inline-insns-auto when inline heuristics
               hints that inlining is very profitable (will enable later
               optimizations).

           uninlined-thunk-insns
           uninlined-thunk-time
               Same as --param uninlined-function-insns and --param uninlined-
               function-time but applied to function thunks

           inline-min-speedup
               When estimated performance improvement of caller + callee runtime
               exceeds this threshold (in percent), the function can be inlined
               regardless of the limit on --param max-inline-insns-single and
               --param max-inline-insns-auto.

           large-function-insns
               The limit specifying really large functions.  For functions
               larger than this limit after inlining, inlining is constrained by
               --param large-function-growth.  This parameter is useful
               primarily to avoid extreme compilation time caused by non-linear
               algorithms used by the back end.

           large-function-growth
               Specifies maximal growth of large function caused by inlining in
               percents.  For example, parameter value 100 limits large function
               growth to 2.0 times the original size.

           large-unit-insns
               The limit specifying large translation unit.  Growth caused by
               inlining of units larger than this limit is limited by --param
               inline-unit-growth.  For small units this might be too tight.
               For example, consider a unit consisting of function A that is
               inline and B that just calls A three times.  If B is small
               relative to A, the growth of unit is 300\% and yet such inlining
               is very sane.  For very large units consisting of small
               inlineable functions, however, the overall unit growth limit is
               needed to avoid exponential explosion of code size.  Thus for
               smaller units, the size is increased to --param large-unit-insns
               before applying --param inline-unit-growth.

           lazy-modules
               Maximum number of concurrently open C++ module files when lazy
               loading.

           inline-unit-growth
               Specifies maximal overall growth of the compilation unit caused
               by inlining.  For example, parameter value 20 limits unit growth
               to 1.2 times the original size. Cold functions (either marked
               cold via an attribute or by profile feedback) are not accounted
               into the unit size.

           ipa-cp-unit-growth
               Specifies maximal overall growth of the compilation unit caused
               by interprocedural constant propagation.  For example, parameter
               value 10 limits unit growth to 1.1 times the original size.

           ipa-cp-large-unit-insns
               The size of translation unit that IPA-CP pass considers large.

           large-stack-frame
               The limit specifying large stack frames.  While inlining the
               algorithm is trying to not grow past this limit too much.

           large-stack-frame-growth
               Specifies maximal growth of large stack frames caused by inlining
               in percents.  For example, parameter value 1000 limits large
               stack frame growth to 11 times the original size.

           max-inline-insns-recursive
           max-inline-insns-recursive-auto
               Specifies the maximum number of instructions an out-of-line copy
               of a self-recursive inline function can grow into by performing
               recursive inlining.

               --param max-inline-insns-recursive applies to functions declared
               inline.  For functions not declared inline, recursive inlining
               happens only when -finline-functions (included in -O3) is
               enabled; --param max-inline-insns-recursive-auto applies instead.

           max-inline-recursive-depth
           max-inline-recursive-depth-auto
               Specifies the maximum recursion depth used for recursive
               inlining.

               --param max-inline-recursive-depth applies to functions declared
               inline.  For functions not declared inline, recursive inlining
               happens only when -finline-functions (included in -O3) is
               enabled; --param max-inline-recursive-depth-auto applies instead.

           min-inline-recursive-probability
               Recursive inlining is profitable only for function having deep
               recursion in average and can hurt for function having little
               recursion depth by increasing the prologue size or complexity of
               function body to other optimizers.

               When profile feedback is available (see -fprofile-generate) the
               actual recursion depth can be guessed from the probability that
               function recurses via a given call expression.  This parameter
               limits inlining only to call expressions whose probability
               exceeds the given threshold (in percents).

           early-inlining-insns
               Specify growth that the early inliner can make.  In effect it
               increases the amount of inlining for code having a large
               abstraction penalty.

           max-early-inliner-iterations
               Limit of iterations of the early inliner.  This basically bounds
               the number of nested indirect calls the early inliner can
               resolve.  Deeper chains are still handled by late inlining.

           comdat-sharing-probability
               Probability (in percent) that C++ inline function with comdat
               visibility are shared across multiple compilation units.

           modref-max-bases
           modref-max-refs
           modref-max-accesses
               Specifies the maximal number of base pointers, references and
               accesses stored for a single function by mod/ref analysis.

           modref-max-tests
               Specifies the maxmal number of tests alias oracle can perform to
               disambiguate memory locations using the mod/ref information.
               This parameter ought to be bigger than --param modref-max-bases
               and --param modref-max-refs.

           modref-max-depth
               Specifies the maximum depth of DFS walk used by modref escape
               analysis.  Setting to 0 disables the analysis completely.

           modref-max-escape-points
               Specifies the maximum number of escape points tracked by modref
               per SSA-name.

           profile-func-internal-id
               A parameter to control whether to use function internal id in
               profile database lookup. If the value is 0, the compiler uses an
               id that is based on function assembler name and filename, which
               makes old profile data more tolerant to source changes such as
               function reordering etc.

           min-vect-loop-bound
               The minimum number of iterations under which loops are not
               vectorized when -ftree-vectorize is used.  The number of
               iterations after vectorization needs to be greater than the value
               specified by this option to allow vectorization.

           gcse-cost-distance-ratio
               Scaling factor in calculation of maximum distance an expression
               can be moved by GCSE optimizations.  This is currently supported
               only in the code hoisting pass.  The bigger the ratio, the more
               aggressive code hoisting is with simple expressions, i.e., the
               expressions that have cost less than gcse-unrestricted-cost.
               Specifying 0 disables hoisting of simple expressions.

           gcse-unrestricted-cost
               Cost, roughly measured as the cost of a single typical machine
               instruction, at which GCSE optimizations do not constrain the
               distance an expression can travel.  This is currently supported
               only in the code hoisting pass.  The lesser the cost, the more
               aggressive code hoisting is.  Specifying 0 allows all expressions
               to travel unrestricted distances.

           max-hoist-depth
               The depth of search in the dominator tree for expressions to
               hoist.  This is used to avoid quadratic behavior in hoisting
               algorithm.  The value of 0 does not limit on the search, but may
               slow down compilation of huge functions.

           max-tail-merge-comparisons
               The maximum amount of similar bbs to compare a bb with.  This is
               used to avoid quadratic behavior in tree tail merging.

           max-tail-merge-iterations
               The maximum amount of iterations of the pass over the function.
               This is used to limit compilation time in tree tail merging.

           store-merging-allow-unaligned
               Allow the store merging pass to introduce unaligned stores if it
               is legal to do so.

           max-stores-to-merge
               The maximum number of stores to attempt to merge into wider
               stores in the store merging pass.

           max-store-chains-to-track
               The maximum number of store chains to track at the same time in
               the attempt to merge them into wider stores in the store merging
               pass.

           max-stores-to-track
               The maximum number of stores to track at the same time in the
               attemt to to merge them into wider stores in the store merging
               pass.

           max-unrolled-insns
               The maximum number of instructions that a loop may have to be
               unrolled.  If a loop is unrolled, this parameter also determines
               how many times the loop code is unrolled.

           max-average-unrolled-insns
               The maximum number of instructions biased by probabilities of
               their execution that a loop may have to be unrolled.  If a loop
               is unrolled, this parameter also determines how many times the
               loop code is unrolled.

           max-unroll-times
               The maximum number of unrollings of a single loop.

           max-peeled-insns
               The maximum number of instructions that a loop may have to be
               peeled.  If a loop is peeled, this parameter also determines how
               many times the loop code is peeled.

           max-peel-times
               The maximum number of peelings of a single loop.

           max-peel-branches
               The maximum number of branches on the hot path through the peeled
               sequence.

           max-completely-peeled-insns
               The maximum number of insns of a completely peeled loop.

           max-completely-peel-times
               The maximum number of iterations of a loop to be suitable for
               complete peeling.

           max-completely-peel-loop-nest-depth
               The maximum depth of a loop nest suitable for complete peeling.

           max-unswitch-insns
               The maximum number of insns of an unswitched loop.

           max-unswitch-level
               The maximum number of branches unswitched in a single loop.

           lim-expensive
               The minimum cost of an expensive expression in the loop invariant
               motion.

           min-loop-cond-split-prob
               When FDO profile information is available, min-loop-cond-split-
               prob specifies minimum threshold for probability of semi-
               invariant condition statement to trigger loop split.

           iv-consider-all-candidates-bound
               Bound on number of candidates for induction variables, below
               which all candidates are considered for each use in induction
               variable optimizations.  If there are more candidates than this,
               only the most relevant ones are considered to avoid quadratic
               time complexity.

           iv-max-considered-uses
               The induction variable optimizations give up on loops that
               contain more induction variable uses.

           iv-always-prune-cand-set-bound
               If the number of candidates in the set is smaller than this
               value, always try to remove unnecessary ivs from the set when
               adding a new one.

           avg-loop-niter
               Average number of iterations of a loop.

           dse-max-object-size
               Maximum size (in bytes) of objects tracked bytewise by dead store
               elimination.  Larger values may result in larger compilation
               times.

           dse-max-alias-queries-per-store
               Maximum number of queries into the alias oracle per store.
               Larger values result in larger compilation times and may result
               in more removed dead stores.

           scev-max-expr-size
               Bound on size of expressions used in the scalar evolutions
               analyzer.  Large expressions slow the analyzer.

           scev-max-expr-complexity
               Bound on the complexity of the expressions in the scalar
               evolutions analyzer.  Complex expressions slow the analyzer.

           max-tree-if-conversion-phi-args
               Maximum number of arguments in a PHI supported by TREE if
               conversion unless the loop is marked with simd pragma.

           vect-max-version-for-alignment-checks
               The maximum number of run-time checks that can be performed when
               doing loop versioning for alignment in the vectorizer.

           vect-max-version-for-alias-checks
               The maximum number of run-time checks that can be performed when
               doing loop versioning for alias in the vectorizer.

           vect-max-peeling-for-alignment
               The maximum number of loop peels to enhance access alignment for
               vectorizer. Value -1 means no limit.

           max-iterations-to-track
               The maximum number of iterations of a loop the brute-force
               algorithm for analysis of the number of iterations of the loop
               tries to evaluate.

           hot-bb-count-fraction
               The denominator n of fraction 1/n of the maximal execution count
               of a basic block in the entire program that a basic block needs
               to at least have in order to be considered hot.  The default is
               10000, which means that a basic block is considered hot if its
               execution count is greater than 1/10000 of the maximal execution
               count.  0 means that it is never considered hot.  Used in non-LTO
               mode.

           hot-bb-count-ws-permille
               The number of most executed permilles, ranging from 0 to 1000, of
               the profiled execution of the entire program to which the
               execution count of a basic block must be part of in order to be
               considered hot.  The default is 990, which means that a basic
               block is considered hot if its execution count contributes to the
               upper 990 permilles, or 99.0%, of the profiled execution of the
               entire program.  0 means that it is never considered hot.  Used
               in LTO mode.

           hot-bb-frequency-fraction
               The denominator n of fraction 1/n of the execution frequency of
               the entry block of a function that a basic block of this function
               needs to at least have in order to be considered hot.  The
               default is 1000, which means that a basic block is considered hot
               in a function if it is executed more frequently than 1/1000 of
               the frequency of the entry block of the function.  0 means that
               it is never considered hot.

           unlikely-bb-count-fraction
               The denominator n of fraction 1/n of the number of profiled runs
               of the entire program below which the execution count of a basic
               block must be in order for the basic block to be considered
               unlikely executed.  The default is 20, which means that a basic
               block is considered unlikely executed if it is executed in fewer
               than 1/20, or 5%, of the runs of the program.  0 means that it is
               always considered unlikely executed.

           max-predicted-iterations
               The maximum number of loop iterations we predict statically.
               This is useful in cases where a function contains a single loop
               with known bound and another loop with unknown bound.  The known
               number of iterations is predicted correctly, while the unknown
               number of iterations average to roughly 10.  This means that the
               loop without bounds appears artificially cold relative to the
               other one.

           builtin-expect-probability
               Control the probability of the expression having the specified
               value. This parameter takes a percentage (i.e. 0 ... 100) as
               input.

           builtin-string-cmp-inline-length
               The maximum length of a constant string for a builtin string cmp
               call eligible for inlining.

           align-threshold
               Select fraction of the maximal frequency of executions of a basic
               block in a function to align the basic block.

           align-loop-iterations
               A loop expected to iterate at least the selected number of
               iterations is aligned.

           tracer-dynamic-coverage
           tracer-dynamic-coverage-feedback
               This value is used to limit superblock formation once the given
               percentage of executed instructions is covered.  This limits
               unnecessary code size expansion.

               The tracer-dynamic-coverage-feedback parameter is used only when
               profile feedback is available.  The real profiles (as opposed to
               statically estimated ones) are much less balanced allowing the
               threshold to be larger value.

           tracer-max-code-growth
               Stop tail duplication once code growth has reached given
               percentage.  This is a rather artificial limit, as most of the
               duplicates are eliminated later in cross jumping, so it may be
               set to much higher values than is the desired code growth.

           tracer-min-branch-ratio
               Stop reverse growth when the reverse probability of best edge is
               less than this threshold (in percent).

           tracer-min-branch-probability
           tracer-min-branch-probability-feedback
               Stop forward growth if the best edge has probability lower than
               this threshold.

               Similarly to tracer-dynamic-coverage two parameters are provided.
               tracer-min-branch-probability-feedback is used for compilation
               with profile feedback and tracer-min-branch-probability
               compilation without.  The value for compilation with profile
               feedback needs to be more conservative (higher) in order to make
               tracer effective.

           stack-clash-protection-guard-size
               Specify the size of the operating system provided stack guard as
               2 raised to num bytes.  Higher values may reduce the number of
               explicit probes, but a value larger than the operating system
               provided guard will leave code vulnerable to stack clash style
               attacks.

           stack-clash-protection-probe-interval
               Stack clash protection involves probing stack space as it is
               allocated.  This param controls the maximum distance between
               probes into the stack as 2 raised to num bytes.  Higher values
               may reduce the number of explicit probes, but a value larger than
               the operating system provided guard will leave code vulnerable to
               stack clash style attacks.

           max-cse-path-length
               The maximum number of basic blocks on path that CSE considers.

           max-cse-insns
               The maximum number of instructions CSE processes before flushing.

           ggc-min-expand
               GCC uses a garbage collector to manage its own memory allocation.
               This parameter specifies the minimum percentage by which the
               garbage collector's heap should be allowed to expand between
               collections.  Tuning this may improve compilation speed; it has
               no effect on code generation.

               The default is 30% + 70% * (RAM/1GB) with an upper bound of 100%
               when RAM >= 1GB.  If "getrlimit" is available, the notion of
               "RAM" is the smallest of actual RAM and "RLIMIT_DATA" or
               "RLIMIT_AS".  If GCC is not able to calculate RAM on a particular
               platform, the lower bound of 30% is used.  Setting this parameter
               and ggc-min-heapsize to zero causes a full collection to occur at
               every opportunity.  This is extremely slow, but can be useful for
               debugging.

           ggc-min-heapsize
               Minimum size of the garbage collector's heap before it begins
               bothering to collect garbage.  The first collection occurs after
               the heap expands by ggc-min-expand% beyond ggc-min-heapsize.
               Again, tuning this may improve compilation speed, and has no
               effect on code generation.

               The default is the smaller of RAM/8, RLIMIT_RSS, or a limit that
               tries to ensure that RLIMIT_DATA or RLIMIT_AS are not exceeded,
               but with a lower bound of 4096 (four megabytes) and an upper
               bound of 131072 (128 megabytes).  If GCC is not able to calculate
               RAM on a particular platform, the lower bound is used.  Setting
               this parameter very large effectively disables garbage
               collection.  Setting this parameter and ggc-min-expand to zero
               causes a full collection to occur at every opportunity.

           max-reload-search-insns
               The maximum number of instruction reload should look backward for
               equivalent register.  Increasing values mean more aggressive
               optimization, making the compilation time increase with probably
               slightly better performance.

           max-cselib-memory-locations
               The maximum number of memory locations cselib should take into
               account.  Increasing values mean more aggressive optimization,
               making the compilation time increase with probably slightly
               better performance.

           max-sched-ready-insns
               The maximum number of instructions ready to be issued the
               scheduler should consider at any given time during the first
               scheduling pass.  Increasing values mean more thorough searches,
               making the compilation time increase with probably little
               benefit.

           max-sched-region-blocks
               The maximum number of blocks in a region to be considered for
               interblock scheduling.

           max-pipeline-region-blocks
               The maximum number of blocks in a region to be considered for
               pipelining in the selective scheduler.

           max-sched-region-insns
               The maximum number of insns in a region to be considered for
               interblock scheduling.

           max-pipeline-region-insns
               The maximum number of insns in a region to be considered for
               pipelining in the selective scheduler.

           min-spec-prob
               The minimum probability (in percents) of reaching a source block
               for interblock speculative scheduling.

           max-sched-extend-regions-iters
               The maximum number of iterations through CFG to extend regions.
               A value of 0 disables region extensions.

           max-sched-insn-conflict-delay
               The maximum conflict delay for an insn to be considered for
               speculative motion.

           sched-spec-prob-cutoff
               The minimal probability of speculation success (in percents), so
               that speculative insns are scheduled.

           sched-state-edge-prob-cutoff
               The minimum probability an edge must have for the scheduler to
               save its state across it.

           sched-mem-true-dep-cost
               Minimal distance (in CPU cycles) between store and load targeting
               same memory locations.

           selsched-max-lookahead
               The maximum size of the lookahead window of selective scheduling.
               It is a depth of search for available instructions.

           selsched-max-sched-times
               The maximum number of times that an instruction is scheduled
               during selective scheduling.  This is the limit on the number of
               iterations through which the instruction may be pipelined.

           selsched-insns-to-rename
               The maximum number of best instructions in the ready list that
               are considered for renaming in the selective scheduler.

           sms-min-sc
               The minimum value of stage count that swing modulo scheduler
               generates.

           max-last-value-rtl
               The maximum size measured as number of RTLs that can be recorded
               in an expression in combiner for a pseudo register as last known
               value of that register.

           max-combine-insns
               The maximum number of instructions the RTL combiner tries to
               combine.

           integer-share-limit
               Small integer constants can use a shared data structure, reducing
               the compiler's memory usage and increasing its speed.  This sets
               the maximum value of a shared integer constant.

           ssp-buffer-size
               The minimum size of buffers (i.e. arrays) that receive stack
               smashing protection when -fstack-protection is used.

           min-size-for-stack-sharing
               The minimum size of variables taking part in stack slot sharing
               when not optimizing.

           max-jump-thread-duplication-stmts
               Maximum number of statements allowed in a block that needs to be
               duplicated when threading jumps.

           max-fields-for-field-sensitive
               Maximum number of fields in a structure treated in a field
               sensitive manner during pointer analysis.

           prefetch-latency
               Estimate on average number of instructions that are executed
               before prefetch finishes.  The distance prefetched ahead is
               proportional to this constant.  Increasing this number may also
               lead to less streams being prefetched (see simultaneous-
               prefetches).

           simultaneous-prefetches
               Maximum number of prefetches that can run at the same time.

           l1-cache-line-size
               The size of cache line in L1 data cache, in bytes.

           l1-cache-size
               The size of L1 data cache, in kilobytes.

           l2-cache-size
               The size of L2 data cache, in kilobytes.

           prefetch-dynamic-strides
               Whether the loop array prefetch pass should issue software
               prefetch hints for strides that are non-constant.  In some cases
               this may be beneficial, though the fact the stride is non-
               constant may make it hard to predict when there is clear benefit
               to issuing these hints.

               Set to 1 if the prefetch hints should be issued for non-constant
               strides.  Set to 0 if prefetch hints should be issued only for
               strides that are known to be constant and below prefetch-minimum-
               stride.

           prefetch-minimum-stride
               Minimum constant stride, in bytes, to start using prefetch hints
               for.  If the stride is less than this threshold, prefetch hints
               will not be issued.

               This setting is useful for processors that have hardware
               prefetchers, in which case there may be conflicts between the
               hardware prefetchers and the software prefetchers.  If the
               hardware prefetchers have a maximum stride they can handle, it
               should be used here to improve the use of software prefetchers.

               A value of -1 means we don't have a threshold and therefore
               prefetch hints can be issued for any constant stride.

               This setting is only useful for strides that are known and
               constant.

           loop-interchange-max-num-stmts
               The maximum number of stmts in a loop to be interchanged.

           loop-interchange-stride-ratio
               The minimum ratio between stride of two loops for interchange to
               be profitable.

           min-insn-to-prefetch-ratio
               The minimum ratio between the number of instructions and the
               number of prefetches to enable prefetching in a loop.

           prefetch-min-insn-to-mem-ratio
               The minimum ratio between the number of instructions and the
               number of memory references to enable prefetching in a loop.

           use-canonical-types
               Whether the compiler should use the "canonical" type system.
               Should always be 1, which uses a more efficient internal
               mechanism for comparing types in C++ and Objective-C++.  However,
               if bugs in the canonical type system are causing compilation
               failures, set this value to 0 to disable canonical types.

           switch-conversion-max-branch-ratio
               Switch initialization conversion refuses to create arrays that
               are bigger than switch-conversion-max-branch-ratio times the
               number of branches in the switch.

           max-partial-antic-length
               Maximum length of the partial antic set computed during the tree
               partial redundancy elimination optimization (-ftree-pre) when
               optimizing at -O3 and above.  For some sorts of source code the
               enhanced partial redundancy elimination optimization can run
               away, consuming all of the memory available on the host machine.
               This parameter sets a limit on the length of the sets that are
               computed, which prevents the runaway behavior.  Setting a value
               of 0 for this parameter allows an unlimited set length.

           rpo-vn-max-loop-depth
               Maximum loop depth that is value-numbered optimistically.  When
               the limit hits the innermost rpo-vn-max-loop-depth loops and the
               outermost loop in the loop nest are value-numbered optimistically
               and the remaining ones not.

           sccvn-max-alias-queries-per-access
               Maximum number of alias-oracle queries we perform when looking
               for redundancies for loads and stores.  If this limit is hit the
               search is aborted and the load or store is not considered
               redundant.  The number of queries is algorithmically limited to
               the number of stores on all paths from the load to the function
               entry.

           ira-max-loops-num
               IRA uses regional register allocation by default.  If a function
               contains more loops than the number given by this parameter, only
               at most the given number of the most frequently-executed loops
               form regions for regional register allocation.

           ira-max-conflict-table-size
               Although IRA uses a sophisticated algorithm to compress the
               conflict table, the table can still require excessive amounts of
               memory for huge functions.  If the conflict table for a function
               could be more than the size in MB given by this parameter, the
               register allocator instead uses a faster, simpler, and lower-
               quality algorithm that does not require building a pseudo-
               register conflict table.

           ira-loop-reserved-regs
               IRA can be used to evaluate more accurate register pressure in
               loops for decisions to move loop invariants (see -O3).  The
               number of available registers reserved for some other purposes is
               given by this parameter.  Default of the parameter is the best
               found from numerous experiments.

           lra-inheritance-ebb-probability-cutoff
               LRA tries to reuse values reloaded in registers in subsequent
               insns.  This optimization is called inheritance.  EBB is used as
               a region to do this optimization.  The parameter defines a
               minimal fall-through edge probability in percentage used to add
               BB to inheritance EBB in LRA.  The default value was chosen from
               numerous runs of SPEC2000 on x86-64.

           loop-invariant-max-bbs-in-loop
               Loop invariant motion can be very expensive, both in compilation
               time and in amount of needed compile-time memory, with very large
               loops.  Loops with more basic blocks than this parameter won't
               have loop invariant motion optimization performed on them.

           loop-max-datarefs-for-datadeps
               Building data dependencies is expensive for very large loops.
               This parameter limits the number of data references in loops that
               are considered for data dependence analysis.  These large loops
               are no handled by the optimizations using loop data dependencies.

           max-vartrack-size
               Sets a maximum number of hash table slots to use during variable
               tracking dataflow analysis of any function.  If this limit is
               exceeded with variable tracking at assignments enabled, analysis
               for that function is retried without it, after removing all debug
               insns from the function.  If the limit is exceeded even without
               debug insns, var tracking analysis is completely disabled for the
               function.  Setting the parameter to zero makes it unlimited.

           max-vartrack-expr-depth
               Sets a maximum number of recursion levels when attempting to map
               variable names or debug temporaries to value expressions.  This
               trades compilation time for more complete debug information.  If
               this is set too low, value expressions that are available and
               could be represented in debug information may end up not being
               used; setting this higher may enable the compiler to find more
               complex debug expressions, but compile time and memory use may
               grow.

           max-debug-marker-count
               Sets a threshold on the number of debug markers (e.g. begin stmt
               markers) to avoid complexity explosion at inlining or expanding
               to RTL.  If a function has more such gimple stmts than the set
               limit, such stmts will be dropped from the inlined copy of a
               function, and from its RTL expansion.

           min-nondebug-insn-uid
               Use uids starting at this parameter for nondebug insns.  The
               range below the parameter is reserved exclusively for debug insns
               created by -fvar-tracking-assignments, but debug insns may get
               (non-overlapping) uids above it if the reserved range is
               exhausted.

           ipa-sra-ptr-growth-factor
               IPA-SRA replaces a pointer to an aggregate with one or more new
               parameters only when their cumulative size is less or equal to
               ipa-sra-ptr-growth-factor times the size of the original pointer
               parameter.

           ipa-sra-max-replacements
               Maximum pieces of an aggregate that IPA-SRA tracks.  As a
               consequence, it is also the maximum number of replacements of a
               formal parameter.

           sra-max-scalarization-size-Ospeed
           sra-max-scalarization-size-Osize
               The two Scalar Reduction of Aggregates passes (SRA and IPA-SRA)
               aim to replace scalar parts of aggregates with uses of
               independent scalar variables.  These parameters control the
               maximum size, in storage units, of aggregate which is considered
               for replacement when compiling for speed (sra-max-scalarization-
               size-Ospeed) or size (sra-max-scalarization-size-Osize)
               respectively.

           sra-max-propagations
               The maximum number of artificial accesses that Scalar Replacement
               of Aggregates (SRA) will track, per one local variable, in order
               to facilitate copy propagation.

           tm-max-aggregate-size
               When making copies of thread-local variables in a transaction,
               this parameter specifies the size in bytes after which variables
               are saved with the logging functions as opposed to save/restore
               code sequence pairs.  This option only applies when using
               -fgnu-tm.

           graphite-max-nb-scop-params
               To avoid exponential effects in the Graphite loop transforms, the
               number of parameters in a Static Control Part (SCoP) is bounded.
               A value of zero can be used to lift the bound.  A variable whose
               value is unknown at compilation time and defined outside a SCoP
               is a parameter of the SCoP.

           loop-block-tile-size
               Loop blocking or strip mining transforms, enabled with
               -floop-block or -floop-strip-mine, strip mine each loop in the
               loop nest by a given number of iterations.  The strip length can
               be changed using the loop-block-tile-size parameter.

           ipa-jump-function-lookups
               Specifies number of statements visited during jump function
               offset discovery.

           ipa-cp-value-list-size
               IPA-CP attempts to track all possible values and types passed to
               a function's parameter in order to propagate them and perform
               devirtualization.  ipa-cp-value-list-size is the maximum number
               of values and types it stores per one formal parameter of a
               function.

           ipa-cp-eval-threshold
               IPA-CP calculates its own score of cloning profitability
               heuristics and performs those cloning opportunities with scores
               that exceed ipa-cp-eval-threshold.

           ipa-cp-max-recursive-depth
               Maximum depth of recursive cloning for self-recursive function.

           ipa-cp-min-recursive-probability
               Recursive cloning only when the probability of call being
               executed exceeds the parameter.

           ipa-cp-recursion-penalty
               Percentage penalty the recursive functions will receive when they
               are evaluated for cloning.

           ipa-cp-single-call-penalty
               Percentage penalty functions containing a single call to another
               function will receive when they are evaluated for cloning.

           ipa-max-agg-items
               IPA-CP is also capable to propagate a number of scalar values
               passed in an aggregate. ipa-max-agg-items controls the maximum
               number of such values per one parameter.

           ipa-cp-loop-hint-bonus
               When IPA-CP determines that a cloning candidate would make the
               number of iterations of a loop known, it adds a bonus of ipa-cp-
               loop-hint-bonus to the profitability score of the candidate.

           ipa-max-loop-predicates
               The maximum number of different predicates IPA will use to
               describe when loops in a function have known properties.

           ipa-max-aa-steps
               During its analysis of function bodies, IPA-CP employs alias
               analysis in order to track values pointed to by function
               parameters.  In order not spend too much time analyzing huge
               functions, it gives up and consider all memory clobbered after
               examining ipa-max-aa-steps statements modifying memory.

           ipa-max-switch-predicate-bounds
               Maximal number of boundary endpoints of case ranges of switch
               statement.  For switch exceeding this limit, IPA-CP will not
               construct cloning cost predicate, which is used to estimate
               cloning benefit, for default case of the switch statement.

           ipa-max-param-expr-ops
               IPA-CP will analyze conditional statement that references some
               function parameter to estimate benefit for cloning upon certain
               constant value.  But if number of operations in a parameter
               expression exceeds ipa-max-param-expr-ops, the expression is
               treated as complicated one, and is not handled by IPA analysis.

           lto-partitions
               Specify desired number of partitions produced during WHOPR
               compilation.  The number of partitions should exceed the number
               of CPUs used for compilation.

           lto-min-partition
               Size of minimal partition for WHOPR (in estimated instructions).
               This prevents expenses of splitting very small programs into too
               many partitions.

           lto-max-partition
               Size of max partition for WHOPR (in estimated instructions).  to
               provide an upper bound for individual size of partition.  Meant
               to be used only with balanced partitioning.

           lto-max-streaming-parallelism
               Maximal number of parallel processes used for LTO streaming.

           cxx-max-namespaces-for-diagnostic-help
               The maximum number of namespaces to consult for suggestions when
               C++ name lookup fails for an identifier.

           sink-frequency-threshold
               The maximum relative execution frequency (in percents) of the
               target block relative to a statement's original block to allow
               statement sinking of a statement.  Larger numbers result in more
               aggressive statement sinking.  A small positive adjustment is
               applied for statements with memory operands as those are even
               more profitable so sink.

           max-stores-to-sink
               The maximum number of conditional store pairs that can be sunk.
               Set to 0 if either vectorization (-ftree-vectorize) or if-
               conversion (-ftree-loop-if-convert) is disabled.

           case-values-threshold
               The smallest number of different values for which it is best to
               use a jump-table instead of a tree of conditional branches.  If
               the value is 0, use the default for the machine.

           jump-table-max-growth-ratio-for-size
               The maximum code size growth ratio when expanding into a jump
               table (in percent).  The parameter is used when optimizing for
               size.

           jump-table-max-growth-ratio-for-speed
               The maximum code size growth ratio when expanding into a jump
               table (in percent).  The parameter is used when optimizing for
               speed.

           tree-reassoc-width
               Set the maximum number of instructions executed in parallel in
               reassociated tree. This parameter overrides target dependent
               heuristics used by default if has non zero value.

           sched-pressure-algorithm
               Choose between the two available implementations of
               -fsched-pressure.  Algorithm 1 is the original implementation and
               is the more likely to prevent instructions from being reordered.
               Algorithm 2 was designed to be a compromise between the
               relatively conservative approach taken by algorithm 1 and the
               rather aggressive approach taken by the default scheduler.  It
               relies more heavily on having a regular register file and
               accurate register pressure classes.  See haifa-sched.c in the GCC
               sources for more details.

               The default choice depends on the target.

           max-slsr-cand-scan
               Set the maximum number of existing candidates that are considered
               when seeking a basis for a new straight-line strength reduction
               candidate.

           asan-globals
               Enable buffer overflow detection for global objects.  This kind
               of protection is enabled by default if you are using
               -fsanitize=address option.  To disable global objects protection
               use --param asan-globals=0.

           asan-stack
               Enable buffer overflow detection for stack objects.  This kind of
               protection is enabled by default when using -fsanitize=address.
               To disable stack protection use --param asan-stack=0 option.

           asan-instrument-reads
               Enable buffer overflow detection for memory reads.  This kind of
               protection is enabled by default when using -fsanitize=address.
               To disable memory reads protection use --param
               asan-instrument-reads=0.

           asan-instrument-writes
               Enable buffer overflow detection for memory writes.  This kind of
               protection is enabled by default when using -fsanitize=address.
               To disable memory writes protection use --param
               asan-instrument-writes=0 option.

           asan-memintrin
               Enable detection for built-in functions.  This kind of protection
               is enabled by default when using -fsanitize=address.  To disable
               built-in functions protection use --param asan-memintrin=0.

           asan-use-after-return
               Enable detection of use-after-return.  This kind of protection is
               enabled by default when using the -fsanitize=address option.  To
               disable it use --param asan-use-after-return=0.

               Note: By default the check is disabled at run time.  To enable
               it, add "detect_stack_use_after_return=1" to the environment
               variable ASAN_OPTIONS.

           asan-instrumentation-with-call-threshold
               If number of memory accesses in function being instrumented is
               greater or equal to this number, use callbacks instead of inline
               checks.  E.g. to disable inline code use --param
               asan-instrumentation-with-call-threshold=0.

           hwasan-instrument-stack
               Enable hwasan instrumentation of statically sized stack-allocated
               variables.  This kind of instrumentation is enabled by default
               when using -fsanitize=hwaddress and disabled by default when
               using -fsanitize=kernel-hwaddress.  To disable stack
               instrumentation use --param hwasan-instrument-stack=0, and to
               enable it use --param hwasan-instrument-stack=1.

           hwasan-random-frame-tag
               When using stack instrumentation, decide tags for stack variables
               using a deterministic sequence beginning at a random tag for each
               frame.  With this parameter unset tags are chosen using the same
               sequence but beginning from 1.  This is enabled by default for
               -fsanitize=hwaddress and unavailable for
               -fsanitize=kernel-hwaddress.  To disable it use --param
               hwasan-random-frame-tag=0.

           hwasan-instrument-allocas
               Enable hwasan instrumentation of dynamically sized stack-
               allocated variables.  This kind of instrumentation is enabled by
               default when using -fsanitize=hwaddress and disabled by default
               when using -fsanitize=kernel-hwaddress.  To disable
               instrumentation of such variables use --param
               hwasan-instrument-allocas=0, and to enable it use --param
               hwasan-instrument-allocas=1.

           hwasan-instrument-reads
               Enable hwasan checks on memory reads.  Instrumentation of reads
               is enabled by default for both -fsanitize=hwaddress and
               -fsanitize=kernel-hwaddress.  To disable checking memory reads
               use --param hwasan-instrument-reads=0.

           hwasan-instrument-writes
               Enable hwasan checks on memory writes.  Instrumentation of writes
               is enabled by default for both -fsanitize=hwaddress and
               -fsanitize=kernel-hwaddress.  To disable checking memory writes
               use --param hwasan-instrument-writes=0.

           hwasan-instrument-mem-intrinsics
               Enable hwasan instrumentation of builtin functions.
               Instrumentation of these builtin functions is enabled by default
               for both -fsanitize=hwaddress and -fsanitize=kernel-hwaddress.
               To disable instrumentation of builtin functions use --param
               hwasan-instrument-mem-intrinsics=0.

           use-after-scope-direct-emission-threshold
               If the size of a local variable in bytes is smaller or equal to
               this number, directly poison (or unpoison) shadow memory instead
               of using run-time callbacks.

           tsan-distinguish-volatile
               Emit special instrumentation for accesses to volatiles.

           tsan-instrument-func-entry-exit
               Emit instrumentation calls to __tsan_func_entry() and
               __tsan_func_exit().

           max-fsm-thread-path-insns
               Maximum number of instructions to copy when duplicating blocks on
               a finite state automaton jump thread path.

           max-fsm-thread-length
               Maximum number of basic blocks on a finite state automaton jump
               thread path.

           max-fsm-thread-paths
               Maximum number of new jump thread paths to create for a finite
               state automaton.

           parloops-chunk-size
               Chunk size of omp schedule for loops parallelized by parloops.

           parloops-schedule
               Schedule type of omp schedule for loops parallelized by parloops
               (static, dynamic, guided, auto, runtime).

           parloops-min-per-thread
               The minimum number of iterations per thread of an innermost
               parallelized loop for which the parallelized variant is preferred
               over the single threaded one.  Note that for a parallelized loop
               nest the minimum number of iterations of the outermost loop per
               thread is two.

           max-ssa-name-query-depth
               Maximum depth of recursion when querying properties of SSA names
               in things like fold routines.  One level of recursion corresponds
               to following a use-def chain.

           max-speculative-devirt-maydefs
               The maximum number of may-defs we analyze when looking for a
               must-def specifying the dynamic type of an object that invokes a
               virtual call we may be able to devirtualize speculatively.

           max-vrp-switch-assertions
               The maximum number of assertions to add along the default edge of
               a switch statement during VRP.

           evrp-mode
               Specifies the mode Early VRP should operate in.

           unroll-jam-min-percent
               The minimum percentage of memory references that must be
               optimized away for the unroll-and-jam transformation to be
               considered profitable.

           unroll-jam-max-unroll
               The maximum number of times the outer loop should be unrolled by
               the unroll-and-jam transformation.

           max-rtl-if-conversion-unpredictable-cost
               Maximum permissible cost for the sequence that would be generated
               by the RTL if-conversion pass for a branch that is considered
               unpredictable.

           max-variable-expansions-in-unroller
               If -fvariable-expansion-in-unroller is used, the maximum number
               of times that an individual variable will be expanded during loop
               unrolling.

           tracer-min-branch-probability-feedback
               Stop forward growth if the probability of best edge is less than
               this threshold (in percent). Used when profile feedback is
               available.

           partial-inlining-entry-probability
               Maximum probability of the entry BB of split region (in percent
               relative to entry BB of the function) to make partial inlining
               happen.

           max-tracked-strlens
               Maximum number of strings for which strlen optimization pass will
               track string lengths.

           gcse-after-reload-partial-fraction
               The threshold ratio for performing partial redundancy elimination
               after reload.

           gcse-after-reload-critical-fraction
               The threshold ratio of critical edges execution count that permit
               performing redundancy elimination after reload.

           max-loop-header-insns
               The maximum number of insns in loop header duplicated by the copy
               loop headers pass.

           vect-epilogues-nomask
               Enable loop epilogue vectorization using smaller vector size.

           vect-partial-vector-usage
               Controls when the loop vectorizer considers using partial vector
               loads and stores as an alternative to falling back to scalar
               code.  0 stops the vectorizer from ever using partial vector
               loads and stores.  1 allows partial vector loads and stores if
               vectorization removes the need for the code to iterate.  2 allows
               partial vector loads and stores in all loops.  The parameter only
               has an effect on targets that support partial vector loads and
               stores.

           avoid-fma-max-bits
               Maximum number of bits for which we avoid creating FMAs.

           sms-loop-average-count-threshold
               A threshold on the average loop count considered by the swing
               modulo scheduler.

           sms-dfa-history
               The number of cycles the swing modulo scheduler considers when
               checking conflicts using DFA.

           max-inline-insns-recursive-auto
               The maximum number of instructions non-inline function can grow
               to via recursive inlining.

           graphite-allow-codegen-errors
               Whether codegen errors should be ICEs when -fchecking.

           sms-max-ii-factor
               A factor for tuning the upper bound that swing modulo scheduler
               uses for scheduling a loop.

           lra-max-considered-reload-pseudos
               The max number of reload pseudos which are considered during
               spilling a non-reload pseudo.

           max-pow-sqrt-depth
               Maximum depth of sqrt chains to use when synthesizing
               exponentiation by a real constant.

           max-dse-active-local-stores
               Maximum number of active local stores in RTL dead store
               elimination.

           asan-instrument-allocas
               Enable asan allocas/VLAs protection.

           max-iterations-computation-cost
               Bound on the cost of an expression to compute the number of
               iterations.

           max-isl-operations
               Maximum number of isl operations, 0 means unlimited.

           graphite-max-arrays-per-scop
               Maximum number of arrays per scop.

           max-vartrack-reverse-op-size
               Max. size of loc list for which reverse ops should be added.

           tracer-dynamic-coverage-feedback
               The percentage of function, weighted by execution frequency, that
               must be covered by trace formation.  Used when profile feedback
               is available.

           max-inline-recursive-depth-auto
               The maximum depth of recursive inlining for non-inline functions.

           fsm-scale-path-stmts
               Scale factor to apply to the number of statements in a threading
               path when comparing to the number of (scaled) blocks.

           fsm-maximum-phi-arguments
               Maximum number of arguments a PHI may have before the FSM
               threader will not try to thread through its block.

           uninit-control-dep-attempts
               Maximum number of nested calls to search for control dependencies
               during uninitialized variable analysis.

           sra-max-scalarization-size-Osize
               Maximum size, in storage units, of an aggregate which should be
               considered for scalarization when compiling for size.

           fsm-scale-path-blocks
               Scale factor to apply to the number of blocks in a threading path
               when comparing to the number of (scaled) statements.

           sched-autopref-queue-depth
               Hardware autoprefetcher scheduler model control flag.  Number of
               lookahead cycles the model looks into; at ' ' only enable
               instruction sorting heuristic.

           loop-versioning-max-inner-insns
               The maximum number of instructions that an inner loop can have
               before the loop versioning pass considers it too big to copy.

           loop-versioning-max-outer-insns
               The maximum number of instructions that an outer loop can have
               before the loop versioning pass considers it too big to copy,
               discounting any instructions in inner loops that directly benefit
               from versioning.

           ssa-name-def-chain-limit
               The maximum number of SSA_NAME assignments to follow in
               determining a property of a variable such as its value.  This
               limits the number of iterations or recursive calls GCC performs
               when optimizing certain statements or when determining their
               validity prior to issuing diagnostics.

           store-merging-max-size
               Maximum size of a single store merging region in bytes.

           hash-table-verification-limit
               The number of elements for which hash table verification is done
               for each searched element.

           max-find-base-term-values
               Maximum number of VALUEs handled during a single find_base_term
               call.

           analyzer-max-enodes-per-program-point
               The maximum number of exploded nodes per program point within the
               analyzer, before terminating analysis of that point.

           analyzer-max-constraints
               The maximum number of constraints per state.

           analyzer-min-snodes-for-call-summary
               The minimum number of supernodes within a function for the
               analyzer to consider summarizing its effects at call sites.

           analyzer-max-enodes-for-full-dump
               The maximum depth of exploded nodes that should appear in a dot
               dump before switching to a less verbose format.

           analyzer-max-recursion-depth
               The maximum number of times a callsite can appear in a call stack
               within the analyzer, before terminating analysis of a call that
               would recurse deeper.

           analyzer-max-svalue-depth
               The maximum depth of a symbolic value, before approximating the
               value as unknown.

           analyzer-max-infeasible-edges
               The maximum number of infeasible edges to reject before declaring
               a diagnostic as infeasible.

           gimple-fe-computed-hot-bb-threshold
               The number of executions of a basic block which is considered
               hot.  The parameter is used only in GIMPLE FE.

           analyzer-bb-explosion-factor
               The maximum number of 'after supernode' exploded nodes within the
               analyzer per supernode, before terminating analysis.

           ranger-logical-depth
               Maximum depth of logical expression evaluation ranger will look
               through when evaluating outgoing edge ranges.

           openacc-kernels
               Specify mode of OpenACC `kernels' constructs handling.  With
               --param=openacc-kernels=decompose, OpenACC `kernels' constructs
               are decomposed into parts, a sequence of compute constructs, each
               then handled individually.  This is work in progress.  With
               --param=openacc-kernels=parloops, OpenACC `kernels' constructs
               are handled by the parloops pass, en bloc.  This is the current
               default.

           The following choices of name are available on AArch64 targets:

           aarch64-sve-compare-costs
               When vectorizing for SVE, consider using "unpacked" vectors for
               smaller elements and use the cost model to pick the cheapest
               approach.  Also use the cost model to choose between SVE and
               Advanced SIMD vectorization.

               Using unpacked vectors includes storing smaller elements in
               larger containers and accessing elements with extending loads and
               truncating stores.

           aarch64-float-recp-precision
               The number of Newton iterations for calculating the reciprocal
               for float type.  The precision of division is proportional to
               this param when division approximation is enabled.  The default
               value is 1.

           aarch64-double-recp-precision
               The number of Newton iterations for calculating the reciprocal
               for double type.  The precision of division is propotional to
               this param when division approximation is enabled.  The default
               value is 2.

           aarch64-autovec-preference
               Force an ISA selection strategy for auto-vectorization.  Accepts
               values from 0 to 4, inclusive.

               0   Use the default heuristics.

               1   Use only Advanced SIMD for auto-vectorization.

               2   Use only SVE for auto-vectorization.

               3   Use both Advanced SIMD and SVE.  Prefer Advanced SIMD when
                   the costs are deemed equal.

               4   Use both Advanced SIMD and SVE.  Prefer SVE when the costs
                   are deemed equal.

               The default value is 0.

           aarch64-loop-vect-issue-rate-niters
               The tuning for some AArch64 CPUs tries to take both latencies and
               issue rates into account when deciding whether a loop should be
               vectorized using SVE, vectorized using Advanced SIMD, or not
               vectorized at all.  If this parameter is set to n, GCC will not
               use this heuristic for loops that are known to execute in fewer
               than n Advanced SIMD iterations.

   Program Instrumentation Options
       GCC supports a number of command-line options that control adding run-
       time instrumentation to the code it normally generates.  For example, one
       purpose of instrumentation is collect profiling statistics for use in
       finding program hot spots, code coverage analysis, or profile-guided
       optimizations.  Another class of program instrumentation is adding run-
       time checking to detect programming errors like invalid pointer
       dereferences or out-of-bounds array accesses, as well as deliberately
       hostile attacks such as stack smashing or C++ vtable hijacking.  There is
       also a general hook which can be used to implement other forms of tracing
       or function-level instrumentation for debug or program analysis purposes.

       -p
       -pg Generate extra code to write profile information suitable for the
           analysis program prof (for -p) or gprof (for -pg).  You must use this
           option when compiling the source files you want data about, and you
           must also use it when linking.

           You can use the function attribute "no_instrument_function" to
           suppress profiling of individual functions when compiling with these
           options.

       -fprofile-arcs
           Add code so that program flow arcs are instrumented.  During
           execution the program records how many times each branch and call is
           executed and how many times it is taken or returns.  On targets that
           support constructors with priority support, profiling properly
           handles constructors, destructors and C++ constructors (and
           destructors) of classes which are used as a type of a global
           variable.

           When the compiled program exits it saves this data to a file called
           auxname.gcda for each source file.  The data may be used for profile-
           directed optimizations (-fbranch-probabilities), or for test coverage
           analysis (-ftest-coverage).  Each object file's auxname is generated
           from the name of the output file, if explicitly specified and it is
           not the final executable, otherwise it is the basename of the source
           file.  In both cases any suffix is removed (e.g. foo.gcda for input
           file dir/foo.c, or dir/foo.gcda for output file specified as -o
           dir/foo.o).

       --coverage
           This option is used to compile and link code instrumented for
           coverage analysis.  The option is a synonym for -fprofile-arcs
           -ftest-coverage (when compiling) and -lgcov (when linking).  See the
           documentation for those options for more details.

           *   Compile the source files with -fprofile-arcs plus optimization
               and code generation options.  For test coverage analysis, use the
               additional -ftest-coverage option.  You do not need to profile
               every source file in a program.

           *   Compile the source files additionally with -fprofile-abs-path to
               create absolute path names in the .gcno files.  This allows gcov
               to find the correct sources in projects where compilations occur
               with different working directories.

           *   Link your object files with -lgcov or -fprofile-arcs (the latter
               implies the former).

           *   Run the program on a representative workload to generate the arc
               profile information.  This may be repeated any number of times.
               You can run concurrent instances of your program, and provided
               that the file system supports locking, the data files will be
               correctly updated.  Unless a strict ISO C dialect option is in
               effect, "fork" calls are detected and correctly handled without
               double counting.

           *   For profile-directed optimizations, compile the source files
               again with the same optimization and code generation options plus
               -fbranch-probabilities.

           *   For test coverage analysis, use gcov to produce human readable
               information from the .gcno and .gcda files.  Refer to the gcov
               documentation for further information.

           With -fprofile-arcs, for each function of your program GCC creates a
           program flow graph, then finds a spanning tree for the graph.  Only
           arcs that are not on the spanning tree have to be instrumented: the
           compiler adds code to count the number of times that these arcs are
           executed.  When an arc is the only exit or only entrance to a block,
           the instrumentation code can be added to the block; otherwise, a new
           basic block must be created to hold the instrumentation code.

       -ftest-coverage
           Produce a notes file that the gcov code-coverage utility can use to
           show program coverage.  Each source file's note file is called
           auxname.gcno.  Refer to the -fprofile-arcs option above for a
           description of auxname and instructions on how to generate test
           coverage data.  Coverage data matches the source files more closely
           if you do not optimize.

       -fprofile-abs-path
           Automatically convert relative source file names to absolute path
           names in the .gcno files.  This allows gcov to find the correct
           sources in projects where compilations occur with different working
           directories.

       -fprofile-dir=path
           Set the directory to search for the profile data files in to path.
           This option affects only the profile data generated by
           -fprofile-generate, -ftest-coverage, -fprofile-arcs and used by
           -fprofile-use and -fbranch-probabilities and its related options.
           Both absolute and relative paths can be used.  By default, GCC uses
           the current directory as path, thus the profile data file appears in
           the same directory as the object file.  In order to prevent the file
           name clashing, if the object file name is not an absolute path, we
           mangle the absolute path of the sourcename.gcda file and use it as
           the file name of a .gcda file.  See similar option -fprofile-note.

           When an executable is run in a massive parallel environment, it is
           recommended to save profile to different folders.  That can be done
           with variables in path that are exported during run-time:

           %p  process ID.

           %q{VAR}
               value of environment variable VAR

       -fprofile-generate
       -fprofile-generate=path
           Enable options usually used for instrumenting application to produce
           profile useful for later recompilation with profile feedback based
           optimization.  You must use -fprofile-generate both when compiling
           and when linking your program.

           The following options are enabled: -fprofile-arcs, -fprofile-values,
           -finline-functions, and -fipa-bit-cp.

           If path is specified, GCC looks at the path to find the profile
           feedback data files. See -fprofile-dir.

           To optimize the program based on the collected profile information,
           use -fprofile-use.

       -fprofile-info-section
       -fprofile-info-section=name
           Register the profile information in the specified section instead of
           using a constructor/destructor.  The section name is name if it is
           specified, otherwise the section name defaults to ".gcov_info".  A
           pointer to the profile information generated by -fprofile-arcs or
           -ftest-coverage is placed in the specified section for each
           translation unit.  This option disables the profile information
           registration through a constructor and it disables the profile
           information processing through a destructor.  This option is not
           intended to be used in hosted environments such as GNU/Linux.  It
           targets systems with limited resources which do not support
           constructors and destructors.  The linker could collect the input
           sections in a continuous memory block and define start and end
           symbols.  The runtime support could dump the profiling information
           registered in this linker set during program termination to a serial
           line for example.  A GNU linker script example which defines a linker
           output section follows:

                     .gcov_info      :
                     {
                       PROVIDE (__gcov_info_start = .);
                       KEEP (*(.gcov_info))
                       PROVIDE (__gcov_info_end = .);
                     }

       -fprofile-note=path
           If path is specified, GCC saves .gcno file into path location.  If
           you combine the option with multiple source files, the .gcno file
           will be overwritten.

       -fprofile-prefix-path=path
           This option can be used in combination with
           profile-generate=profile_dir and profile-use=profile_dir to inform
           GCC where is the base directory of built source tree.  By default
           profile_dir will contain files with mangled absolute paths of all
           object files in the built project.  This is not desirable when
           directory used to build the instrumented binary differs from the
           directory used to build the binary optimized with profile feedback
           because the profile data will not be found during the optimized
           build.  In such setups -fprofile-prefix-path=path with path pointing
           to the base directory of the build can be used to strip the
           irrelevant part of the path and keep all file names relative to the
           main build directory.

       -fprofile-update=method
           Alter the update method for an application instrumented for profile
           feedback based optimization.  The method argument should be one of
           single, atomic or prefer-atomic.  The first one is useful for single-
           threaded applications, while the second one prevents profile
           corruption by emitting thread-safe code.

           Warning: When an application does not properly join all threads (or
           creates an detached thread), a profile file can be still corrupted.

           Using prefer-atomic would be transformed either to atomic, when
           supported by a target, or to single otherwise.  The GCC driver
           automatically selects prefer-atomic when -pthread is present in the
           command line.

       -fprofile-filter-files=regex
           Instrument only functions from files whose name matches any of the
           regular expressions (separated by semi-colons).

           For example, -fprofile-filter-files=main\.c;module.*\.c will
           instrument only main.c and all C files starting with 'module'.

       -fprofile-exclude-files=regex
           Instrument only functions from files whose name does not match any of
           the regular expressions (separated by semi-colons).

           For example, -fprofile-exclude-files=/usr/.* will prevent
           instrumentation of all files that are located in the /usr/ folder.

       -fprofile-reproducible=[multithreaded|parallel-runs|serial]
           Control level of reproducibility of profile gathered by
           "-fprofile-generate".  This makes it possible to rebuild program with
           same outcome which is useful, for example, for distribution packages.

           With -fprofile-reproducible=serial the profile gathered by
           -fprofile-generate is reproducible provided the trained program
           behaves the same at each invocation of the train run, it is not
           multi-threaded and profile data streaming is always done in the same
           order.  Note that profile streaming happens at the end of program run
           but also before "fork" function is invoked.

           Note that it is quite common that execution counts of some part of
           programs depends, for example, on length of temporary file names or
           memory space randomization (that may affect hash-table collision
           rate).  Such non-reproducible part of programs may be annotated by
           "no_instrument_function" function attribute. gcov-dump with -l can be
           used to dump gathered data and verify that they are indeed
           reproducible.

           With -fprofile-reproducible=parallel-runs collected profile stays
           reproducible regardless the order of streaming of the data into gcda
           files.  This setting makes it possible to run multiple instances of
           instrumented program in parallel (such as with "make -j"). This
           reduces quality of gathered data, in particular of indirect call
           profiling.

       -fsanitize=address
           Enable AddressSanitizer, a fast memory error detector.  Memory access
           instructions are instrumented to detect out-of-bounds and use-after-
           free bugs.  The option enables -fsanitize-address-use-after-scope.
           See <https://github.com/google/sanitizers/wiki/AddressSanitizer> for
           more details.  The run-time behavior can be influenced using the
           ASAN_OPTIONS environment variable.  When set to "help=1", the
           available options are shown at startup of the instrumented program.
           See
           <https://github.com/google/sanitizers/wiki/AddressSanitizerFlags#run-time-flags>
           for a list of supported options.  The option cannot be combined with
           -fsanitize=thread or -fsanitize=hwaddress.  Note that the only target
           -fsanitize=hwaddress is currently supported on is AArch64.

       -fsanitize=kernel-address
           Enable AddressSanitizer for Linux kernel.  See
           <https://github.com/google/kasan> for more details.

       -fsanitize=hwaddress
           Enable Hardware-assisted AddressSanitizer, which uses a hardware
           ability to ignore the top byte of a pointer to allow the detection of
           memory errors with a low memory overhead.  Memory access instructions
           are instrumented to detect out-of-bounds and use-after-free bugs.
           The option enables -fsanitize-address-use-after-scope.  See
           <https://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html>
           for more details.  The run-time behavior can be influenced using the
           HWASAN_OPTIONS environment variable.  When set to "help=1", the
           available options are shown at startup of the instrumented program.
           The option cannot be combined with -fsanitize=thread or
           -fsanitize=address, and is currently only available on AArch64.

       -fsanitize=kernel-hwaddress
           Enable Hardware-assisted AddressSanitizer for compilation of the
           Linux kernel.  Similar to -fsanitize=kernel-address but using an
           alternate instrumentation method, and similar to -fsanitize=hwaddress
           but with instrumentation differences necessary for compiling the
           Linux kernel.  These differences are to avoid hwasan library
           initialization calls and to account for the stack pointer having a
           different value in its top byte.

           Note: This option has different defaults to the -fsanitize=hwaddress.
           Instrumenting the stack and alloca calls are not on by default but
           are still possible by specifying the command-line options --param
           hwasan-instrument-stack=1 and --param hwasan-instrument-allocas=1
           respectively. Using a random frame tag is not implemented for kernel
           instrumentation.

       -fsanitize=pointer-compare
           Instrument comparison operation (<, <=, >, >=) with pointer operands.
           The option must be combined with either -fsanitize=kernel-address or
           -fsanitize=address The option cannot be combined with
           -fsanitize=thread.  Note: By default the check is disabled at run
           time.  To enable it, add "detect_invalid_pointer_pairs=2" to the
           environment variable ASAN_OPTIONS. Using
           "detect_invalid_pointer_pairs=1" detects invalid operation only when
           both pointers are non-null.

       -fsanitize=pointer-subtract
           Instrument subtraction with pointer operands.  The option must be
           combined with either -fsanitize=kernel-address or -fsanitize=address
           The option cannot be combined with -fsanitize=thread.  Note: By
           default the check is disabled at run time.  To enable it, add
           "detect_invalid_pointer_pairs=2" to the environment variable
           ASAN_OPTIONS. Using "detect_invalid_pointer_pairs=1" detects invalid
           operation only when both pointers are non-null.

       -fsanitize=thread
           Enable ThreadSanitizer, a fast data race detector.  Memory access
           instructions are instrumented to detect data race bugs.  See
           <https://github.com/google/sanitizers/wiki#threadsanitizer> for more
           details. The run-time behavior can be influenced using the
           TSAN_OPTIONS environment variable; see
           <https://github.com/google/sanitizers/wiki/ThreadSanitizerFlags> for
           a list of supported options.  The option cannot be combined with
           -fsanitize=address, -fsanitize=leak.

           Note that sanitized atomic builtins cannot throw exceptions when
           operating on invalid memory addresses with non-call exceptions
           (-fnon-call-exceptions).

       -fsanitize=leak
           Enable LeakSanitizer, a memory leak detector.  This option only
           matters for linking of executables and the executable is linked
           against a library that overrides "malloc" and other allocator
           functions.  See
           <https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer>
           for more details.  The run-time behavior can be influenced using the
           LSAN_OPTIONS environment variable.  The option cannot be combined
           with -fsanitize=thread.

       -fsanitize=undefined
           Enable UndefinedBehaviorSanitizer, a fast undefined behavior
           detector.  Various computations are instrumented to detect undefined
           behavior at runtime.  Current suboptions are:

           -fsanitize=shift
               This option enables checking that the result of a shift operation
               is not undefined.  Note that what exactly is considered undefined
               differs slightly between C and C++, as well as between ISO C90
               and C99, etc.  This option has two suboptions,
               -fsanitize=shift-base and -fsanitize=shift-exponent.

           -fsanitize=shift-exponent
               This option enables checking that the second argument of a shift
               operation is not negative and is smaller than the precision of
               the promoted first argument.

           -fsanitize=shift-base
               If the second argument of a shift operation is within range,
               check that the result of a shift operation is not undefined.
               Note that what exactly is considered undefined differs slightly
               between C and C++, as well as between ISO C90 and C99, etc.

           -fsanitize=integer-divide-by-zero
               Detect integer division by zero as well as "INT_MIN / -1"
               division.

           -fsanitize=unreachable
               With this option, the compiler turns the "__builtin_unreachable"
               call into a diagnostics message call instead.  When reaching the
               "__builtin_unreachable" call, the behavior is undefined.

           -fsanitize=vla-bound
               This option instructs the compiler to check that the size of a
               variable length array is positive.

           -fsanitize=null
               This option enables pointer checking.  Particularly, the
               application built with this option turned on will issue an error
               message when it tries to dereference a NULL pointer, or if a
               reference (possibly an rvalue reference) is bound to a NULL
               pointer, or if a method is invoked on an object pointed by a NULL
               pointer.

           -fsanitize=return
               This option enables return statement checking.  Programs built
               with this option turned on will issue an error message when the
               end of a non-void function is reached without actually returning
               a value.  This option works in C++ only.

           -fsanitize=signed-integer-overflow
               This option enables signed integer overflow checking.  We check
               that the result of "+", "*", and both unary and binary "-" does
               not overflow in the signed arithmetics.  Note, integer promotion
               rules must be taken into account.  That is, the following is not
               an overflow:

                       signed char a = SCHAR_MAX;
                       a++;

           -fsanitize=bounds
               This option enables instrumentation of array bounds.  Various out
               of bounds accesses are detected.  Flexible array members,
               flexible array member-like arrays, and initializers of variables
               with static storage are not instrumented.

           -fsanitize=bounds-strict
               This option enables strict instrumentation of array bounds.  Most
               out of bounds accesses are detected, including flexible array
               members and flexible array member-like arrays.  Initializers of
               variables with static storage are not instrumented.

           -fsanitize=alignment
               This option enables checking of alignment of pointers when they
               are dereferenced, or when a reference is bound to insufficiently
               aligned target, or when a method or constructor is invoked on
               insufficiently aligned object.

           -fsanitize=object-size
               This option enables instrumentation of memory references using
               the "__builtin_object_size" function.  Various out of bounds
               pointer accesses are detected.

           -fsanitize=float-divide-by-zero
               Detect floating-point division by zero.  Unlike other similar
               options, -fsanitize=float-divide-by-zero is not enabled by
               -fsanitize=undefined, since floating-point division by zero can
               be a legitimate way of obtaining infinities and NaNs.

           -fsanitize=float-cast-overflow
               This option enables floating-point type to integer conversion
               checking.  We check that the result of the conversion does not
               overflow.  Unlike other similar options,
               -fsanitize=float-cast-overflow is not enabled by
               -fsanitize=undefined.  This option does not work well with
               "FE_INVALID" exceptions enabled.

           -fsanitize=nonnull-attribute
               This option enables instrumentation of calls, checking whether
               null values are not passed to arguments marked as requiring a
               non-null value by the "nonnull" function attribute.

           -fsanitize=returns-nonnull-attribute
               This option enables instrumentation of return statements in
               functions marked with "returns_nonnull" function attribute, to
               detect returning of null values from such functions.

           -fsanitize=bool
               This option enables instrumentation of loads from bool.  If a
               value other than 0/1 is loaded, a run-time error is issued.

           -fsanitize=enum
               This option enables instrumentation of loads from an enum type.
               If a value outside the range of values for the enum type is
               loaded, a run-time error is issued.

           -fsanitize=vptr
               This option enables instrumentation of C++ member function calls,
               member accesses and some conversions between pointers to base and
               derived classes, to verify the referenced object has the correct
               dynamic type.

           -fsanitize=pointer-overflow
               This option enables instrumentation of pointer arithmetics.  If
               the pointer arithmetics overflows, a run-time error is issued.

           -fsanitize=builtin
               This option enables instrumentation of arguments to selected
               builtin functions.  If an invalid value is passed to such
               arguments, a run-time error is issued.  E.g. passing 0 as the
               argument to "__builtin_ctz" or "__builtin_clz" invokes undefined
               behavior and is diagnosed by this option.

           While -ftrapv causes traps for signed overflows to be emitted,
           -fsanitize=undefined gives a diagnostic message.  This currently
           works only for the C family of languages.

       -fno-sanitize=all
           This option disables all previously enabled sanitizers.
           -fsanitize=all is not allowed, as some sanitizers cannot be used
           together.

       -fasan-shadow-offset=number
           This option forces GCC to use custom shadow offset in
           AddressSanitizer checks.  It is useful for experimenting with
           different shadow memory layouts in Kernel AddressSanitizer.

       -fsanitize-sections=s1,s2,...
           Sanitize global variables in selected user-defined sections.  si may
           contain wildcards.

       -fsanitize-recover[=opts]
           -fsanitize-recover= controls error recovery mode for sanitizers
           mentioned in comma-separated list of opts.  Enabling this option for
           a sanitizer component causes it to attempt to continue running the
           program as if no error happened.  This means multiple runtime errors
           can be reported in a single program run, and the exit code of the
           program may indicate success even when errors have been reported.
           The -fno-sanitize-recover= option can be used to alter this behavior:
           only the first detected error is reported and program then exits with
           a non-zero exit code.

           Currently this feature only works for -fsanitize=undefined (and its
           suboptions except for -fsanitize=unreachable and -fsanitize=return),
           -fsanitize=float-cast-overflow, -fsanitize=float-divide-by-zero,
           -fsanitize=bounds-strict, -fsanitize=kernel-address and
           -fsanitize=address.  For these sanitizers error recovery is turned on
           by default, except -fsanitize=address, for which this feature is
           experimental.  -fsanitize-recover=all and -fno-sanitize-recover=all
           is also accepted, the former enables recovery for all sanitizers that
           support it, the latter disables recovery for all sanitizers that
           support it.

           Even if a recovery mode is turned on the compiler side, it needs to
           be also enabled on the runtime library side, otherwise the failures
           are still fatal.  The runtime library defaults to "halt_on_error=0"
           for ThreadSanitizer and UndefinedBehaviorSanitizer, while default
           value for AddressSanitizer is "halt_on_error=1". This can be
           overridden through setting the "halt_on_error" flag in the
           corresponding environment variable.

           Syntax without an explicit opts parameter is deprecated.  It is
           equivalent to specifying an opts list of:

                   undefined,float-cast-overflow,float-divide-by-zero,bounds-strict

       -fsanitize-address-use-after-scope
           Enable sanitization of local variables to detect use-after-scope
           bugs.  The option sets -fstack-reuse to none.

       -fsanitize-undefined-trap-on-error
           The -fsanitize-undefined-trap-on-error option instructs the compiler
           to report undefined behavior using "__builtin_trap" rather than a
           "libubsan" library routine.  The advantage of this is that the
           "libubsan" library is not needed and is not linked in, so this is
           usable even in freestanding environments.

       -fsanitize-coverage=trace-pc
           Enable coverage-guided fuzzing code instrumentation.  Inserts a call
           to "__sanitizer_cov_trace_pc" into every basic block.

       -fsanitize-coverage=trace-cmp
           Enable dataflow guided fuzzing code instrumentation.  Inserts a call
           to "__sanitizer_cov_trace_cmp1", "__sanitizer_cov_trace_cmp2",
           "__sanitizer_cov_trace_cmp4" or "__sanitizer_cov_trace_cmp8" for
           integral comparison with both operands variable or
           "__sanitizer_cov_trace_const_cmp1",
           "__sanitizer_cov_trace_const_cmp2",
           "__sanitizer_cov_trace_const_cmp4" or
           "__sanitizer_cov_trace_const_cmp8" for integral comparison with one
           operand constant, "__sanitizer_cov_trace_cmpf" or
           "__sanitizer_cov_trace_cmpd" for float or double comparisons and
           "__sanitizer_cov_trace_switch" for switch statements.

       -fcf-protection=[full|branch|return|none|check]
           Enable code instrumentation of control-flow transfers to increase
           program security by checking that target addresses of control-flow
           transfer instructions (such as indirect function call, function
           return, indirect jump) are valid.  This prevents diverting the flow
           of control to an unexpected target.  This is intended to protect
           against such threats as Return-oriented Programming (ROP), and
           similarly call/jmp-oriented programming (COP/JOP).

           The value "branch" tells the compiler to implement checking of
           validity of control-flow transfer at the point of indirect branch
           instructions, i.e. call/jmp instructions.  The value "return"
           implements checking of validity at the point of returning from a
           function.  The value "full" is an alias for specifying both "branch"
           and "return". The value "none" turns off instrumentation.

           The value "check" is used for the final link with link-time
           optimization (LTO).  An error is issued if LTO object files are
           compiled with different -fcf-protection values.  The value "check" is
           ignored at the compile time.

           The macro "__CET__" is defined when -fcf-protection is used.  The
           first bit of "__CET__" is set to 1 for the value "branch" and the
           second bit of "__CET__" is set to 1 for the "return".

           You can also use the "nocf_check" attribute to identify which
           functions and calls should be skipped from instrumentation.

           Currently the x86 GNU/Linux target provides an implementation based
           on Intel Control-flow Enforcement Technology (CET).

       -fstack-protector
           Emit extra code to check for buffer overflows, such as stack smashing
           attacks.  This is done by adding a guard variable to functions with
           vulnerable objects.  This includes functions that call "alloca", and
           functions with buffers larger than or equal to 8 bytes.  The guards
           are initialized when a function is entered and then checked when the
           function exits.  If a guard check fails, an error message is printed
           and the program exits.  Only variables that are actually allocated on
           the stack are considered, optimized away variables or variables
           allocated in registers don't count.

       -fstack-protector-all
           Like -fstack-protector except that all functions are protected.

       -fstack-protector-strong
           Like -fstack-protector but includes additional functions to be
           protected --- those that have local array definitions, or have
           references to local frame addresses.  Only variables that are
           actually allocated on the stack are considered, optimized away
           variables or variables allocated in registers don't count.

       -fstack-protector-explicit
           Like -fstack-protector but only protects those functions which have
           the "stack_protect" attribute.

       -fstack-check
           Generate code to verify that you do not go beyond the boundary of the
           stack.  You should specify this flag if you are running in an
           environment with multiple threads, but you only rarely need to
           specify it in a single-threaded environment since stack overflow is
           automatically detected on nearly all systems if there is only one
           stack.

           Note that this switch does not actually cause checking to be done;
           the operating system or the language runtime must do that.  The
           switch causes generation of code to ensure that they see the stack
           being extended.

           You can additionally specify a string parameter: no means no
           checking, generic means force the use of old-style checking, specific
           means use the best checking method and is equivalent to bare
           -fstack-check.

           Old-style checking is a generic mechanism that requires no specific
           target support in the compiler but comes with the following
           drawbacks:

           1.  Modified allocation strategy for large objects: they are always
               allocated dynamically if their size exceeds a fixed threshold.
               Note this may change the semantics of some code.

           2.  Fixed limit on the size of the static frame of functions: when it
               is topped by a particular function, stack checking is not
               reliable and a warning is issued by the compiler.

           3.  Inefficiency: because of both the modified allocation strategy
               and the generic implementation, code performance is hampered.

           Note that old-style stack checking is also the fallback method for
           specific if no target support has been added in the compiler.

           -fstack-check= is designed for Ada's needs to detect infinite
           recursion and stack overflows.  specific is an excellent choice when
           compiling Ada code.  It is not generally sufficient to protect
           against stack-clash attacks.  To protect against those you want
           -fstack-clash-protection.

       -fstack-clash-protection
           Generate code to prevent stack clash style attacks.  When this option
           is enabled, the compiler will only allocate one page of stack space
           at a time and each page is accessed immediately after allocation.
           Thus, it prevents allocations from jumping over any stack guard page
           provided by the operating system.

           Most targets do not fully support stack clash protection.  However,
           on those targets -fstack-clash-protection will protect dynamic stack
           allocations.  -fstack-clash-protection may also provide limited
           protection for static stack allocations if the target supports
           -fstack-check=specific.

       -fstack-limit-register=reg
       -fstack-limit-symbol=sym
       -fno-stack-limit
           Generate code to ensure that the stack does not grow beyond a certain
           value, either the value of a register or the address of a symbol.  If
           a larger stack is required, a signal is raised at run time.  For most
           targets, the signal is raised before the stack overruns the boundary,
           so it is possible to catch the signal without taking special
           precautions.

           For instance, if the stack starts at absolute address 0x80000000 and
           grows downwards, you can use the flags
           -fstack-limit-symbol=__stack_limit and
           -Wl,--defsym,__stack_limit=0x7ffe0000 to enforce a stack limit of
           128KB.  Note that this may only work with the GNU linker.

           You can locally override stack limit checking by using the
           "no_stack_limit" function attribute.

       -fsplit-stack
           Generate code to automatically split the stack before it overflows.
           The resulting program has a discontiguous stack which can only
           overflow if the program is unable to allocate any more memory.  This
           is most useful when running threaded programs, as it is no longer
           necessary to calculate a good stack size to use for each thread.
           This is currently only implemented for the x86 targets running
           GNU/Linux.

           When code compiled with -fsplit-stack calls code compiled without
           -fsplit-stack, there may not be much stack space available for the
           latter code to run.  If compiling all code, including library code,
           with -fsplit-stack is not an option, then the linker can fix up these
           calls so that the code compiled without -fsplit-stack always has a
           large stack.  Support for this is implemented in the gold linker in
           GNU binutils release 2.21 and later.

       -fvtable-verify=[std|preinit|none]
           This option is only available when compiling C++ code.  It turns on
           (or off, if using -fvtable-verify=none) the security feature that
           verifies at run time, for every virtual call, that the vtable pointer
           through which the call is made is valid for the type of the object,
           and has not been corrupted or overwritten.  If an invalid vtable
           pointer is detected at run time, an error is reported and execution
           of the program is immediately halted.

           This option causes run-time data structures to be built at program
           startup, which are used for verifying the vtable pointers.  The
           options std and preinit control the timing of when these data
           structures are built.  In both cases the data structures are built
           before execution reaches "main".  Using -fvtable-verify=std causes
           the data structures to be built after shared libraries have been
           loaded and initialized.  -fvtable-verify=preinit causes them to be
           built before shared libraries have been loaded and initialized.

           If this option appears multiple times in the command line with
           different values specified, none takes highest priority over both std
           and preinit; preinit takes priority over std.

       -fvtv-debug
           When used in conjunction with -fvtable-verify=std or
           -fvtable-verify=preinit, causes debug versions of the runtime
           functions for the vtable verification feature to be called.  This
           flag also causes the compiler to log information about which vtable
           pointers it finds for each class.  This information is written to a
           file named vtv_set_ptr_data.log in the directory named by the
           environment variable VTV_LOGS_DIR if that is defined or the current
           working directory otherwise.

           Note:  This feature appends data to the log file. If you want a fresh
           log file, be sure to delete any existing one.

       -fvtv-counts
           This is a debugging flag.  When used in conjunction with
           -fvtable-verify=std or -fvtable-verify=preinit, this causes the
           compiler to keep track of the total number of virtual calls it
           encounters and the number of verifications it inserts.  It also
           counts the number of calls to certain run-time library functions that
           it inserts and logs this information for each compilation unit.  The
           compiler writes this information to a file named vtv_count_data.log
           in the directory named by the environment variable VTV_LOGS_DIR if
           that is defined or the current working directory otherwise.  It also
           counts the size of the vtable pointer sets for each class, and writes
           this information to vtv_class_set_sizes.log in the same directory.

           Note:  This feature appends data to the log files.  To get fresh log
           files, be sure to delete any existing ones.

       -finstrument-functions
           Generate instrumentation calls for entry and exit to functions.  Just
           after function entry and just before function exit, the following
           profiling functions are called with the address of the current
           function and its call site.  (On some platforms,
           "__builtin_return_address" does not work beyond the current function,
           so the call site information may not be available to the profiling
           functions otherwise.)

                   void __cyg_profile_func_enter (void *this_fn,
                                                  void *call_site);
                   void __cyg_profile_func_exit  (void *this_fn,
                                                  void *call_site);

           The first argument is the address of the start of the current
           function, which may be looked up exactly in the symbol table.

           This instrumentation is also done for functions expanded inline in
           other functions.  The profiling calls indicate where, conceptually,
           the inline function is entered and exited.  This means that
           addressable versions of such functions must be available.  If all
           your uses of a function are expanded inline, this may mean an
           additional expansion of code size.  If you use "extern inline" in
           your C code, an addressable version of such functions must be
           provided.  (This is normally the case anyway, but if you get lucky
           and the optimizer always expands the functions inline, you might have
           gotten away without providing static copies.)

           A function may be given the attribute "no_instrument_function", in
           which case this instrumentation is not done.  This can be used, for
           example, for the profiling functions listed above, high-priority
           interrupt routines, and any functions from which the profiling
           functions cannot safely be called (perhaps signal handlers, if the
           profiling routines generate output or allocate memory).

       -finstrument-functions-exclude-file-list=file,file,...
           Set the list of functions that are excluded from instrumentation (see
           the description of -finstrument-functions).  If the file that
           contains a function definition matches with one of file, then that
           function is not instrumented.  The match is done on substrings: if
           the file parameter is a substring of the file name, it is considered
           to be a match.

           For example:

                   -finstrument-functions-exclude-file-list=/bits/stl,include/sys

           excludes any inline function defined in files whose pathnames contain
           /bits/stl or include/sys.

           If, for some reason, you want to include letter , in one of sym,
           write ,. For example,
           -finstrument-functions-exclude-file-list=',,tmp' (note the single
           quote surrounding the option).

       -finstrument-functions-exclude-function-list=sym,sym,...
           This is similar to -finstrument-functions-exclude-file-list, but this
           option sets the list of function names to be excluded from
           instrumentation.  The function name to be matched is its user-visible
           name, such as "vector<int> blah(const vector<int> &)", not the
           internal mangled name (e.g., "_Z4blahRSt6vectorIiSaIiEE").  The match
           is done on substrings: if the sym parameter is a substring of the
           function name, it is considered to be a match.  For C99 and C++
           extended identifiers, the function name must be given in UTF-8, not
           using universal character names.

       -fpatchable-function-entry=N[,M]
           Generate N NOPs right at the beginning of each function, with the
           function entry point before the Mth NOP.  If M is omitted, it
           defaults to 0 so the function entry points to the address just at the
           first NOP.  The NOP instructions reserve extra space which can be
           used to patch in any desired instrumentation at run time, provided
           that the code segment is writable.  The amount of space is
           controllable indirectly via the number of NOPs; the NOP instruction
           used corresponds to the instruction emitted by the internal GCC back-
           end interface "gen_nop".  This behavior is target-specific and may
           also depend on the architecture variant and/or other compilation
           options.

           For run-time identification, the starting addresses of these areas,
           which correspond to their respective function entries minus M, are
           additionally collected in the "__patchable_function_entries" section
           of the resulting binary.

           Note that the value of "__attribute__ ((patchable_function_entry
           (N,M)))" takes precedence over command-line option
           -fpatchable-function-entry=N,M.  This can be used to increase the
           area size or to remove it completely on a single function.  If "N=0",
           no pad location is recorded.

           The NOP instructions are inserted at---and maybe before, depending on
           M---the function entry address, even before the prologue.

           The maximum value of N and M is 65535.

   Options Controlling the Preprocessor
       These options control the C preprocessor, which is run on each C source
       file before actual compilation.

       If you use the -E option, nothing is done except preprocessing.  Some of
       these options make sense only together with -E because they cause the
       preprocessor output to be unsuitable for actual compilation.

       In addition to the options listed here, there are a number of options to
       control search paths for include files documented in Directory Options.
       Options to control preprocessor diagnostics are listed in Warning
       Options.

       -D name
           Predefine name as a macro, with definition 1.

       -D name=definition
           The contents of definition are tokenized and processed as if they
           appeared during translation phase three in a #define directive.  In
           particular, the definition is truncated by embedded newline
           characters.

           If you are invoking the preprocessor from a shell or shell-like
           program you may need to use the shell's quoting syntax to protect
           characters such as spaces that have a meaning in the shell syntax.

           If you wish to define a function-like macro on the command line,
           write its argument list with surrounding parentheses before the
           equals sign (if any).  Parentheses are meaningful to most shells, so
           you should quote the option.  With sh and csh,
           -D'name(args...)=definition' works.

           -D and -U options are processed in the order they are given on the
           command line.  All -imacros file and -include file options are
           processed after all -D and -U options.

       -U name
           Cancel any previous definition of name, either built in or provided
           with a -D option.

       -include file
           Process file as if "#include "file"" appeared as the first line of
           the primary source file.  However, the first directory searched for
           file is the preprocessor's working directory instead of the directory
           containing the main source file.  If not found there, it is searched
           for in the remainder of the "#include "..."" search chain as normal.

           If multiple -include options are given, the files are included in the
           order they appear on the command line.

       -imacros file
           Exactly like -include, except that any output produced by scanning
           file is thrown away.  Macros it defines remain defined.  This allows
           you to acquire all the macros from a header without also processing
           its declarations.

           All files specified by -imacros are processed before all files
           specified by -include.

       -undef
           Do not predefine any system-specific or GCC-specific macros.  The
           standard predefined macros remain defined.

       -pthread
           Define additional macros required for using the POSIX threads
           library.  You should use this option consistently for both
           compilation and linking.  This option is supported on GNU/Linux
           targets, most other Unix derivatives, and also on x86 Cygwin and
           MinGW targets.

       -M  Instead of outputting the result of preprocessing, output a rule
           suitable for make describing the dependencies of the main source
           file.  The preprocessor outputs one make rule containing the object
           file name for that source file, a colon, and the names of all the
           included files, including those coming from -include or -imacros
           command-line options.

           Unless specified explicitly (with -MT or -MQ), the object file name
           consists of the name of the source file with any suffix replaced with
           object file suffix and with any leading directory parts removed.  If
           there are many included files then the rule is split into several
           lines using \-newline.  The rule has no commands.

           This option does not suppress the preprocessor's debug output, such
           as -dM.  To avoid mixing such debug output with the dependency rules
           you should explicitly specify the dependency output file with -MF, or
           use an environment variable like DEPENDENCIES_OUTPUT.  Debug output
           is still sent to the regular output stream as normal.

           Passing -M to the driver implies -E, and suppresses warnings with an
           implicit -w.

       -MM Like -M but do not mention header files that are found in system
           header directories, nor header files that are included, directly or
           indirectly, from such a header.

           This implies that the choice of angle brackets or double quotes in an
           #include directive does not in itself determine whether that header
           appears in -MM dependency output.

       -MF file
           When used with -M or -MM, specifies a file to write the dependencies
           to.  If no -MF switch is given the preprocessor sends the rules to
           the same place it would send preprocessed output.

           When used with the driver options -MD or -MMD, -MF overrides the
           default dependency output file.

           If file is -, then the dependencies are written to stdout.

       -MG In conjunction with an option such as -M requesting dependency
           generation, -MG assumes missing header files are generated files and
           adds them to the dependency list without raising an error.  The
           dependency filename is taken directly from the "#include" directive
           without prepending any path.  -MG also suppresses preprocessed
           output, as a missing header file renders this useless.

           This feature is used in automatic updating of makefiles.

       -Mno-modules
           Disable dependency generation for compiled module interfaces.

       -MP This option instructs CPP to add a phony target for each dependency
           other than the main file, causing each to depend on nothing.  These
           dummy rules work around errors make gives if you remove header files
           without updating the Makefile to match.

           This is typical output:

                   test.o: test.c test.h

                   test.h:

       -MT target
           Change the target of the rule emitted by dependency generation.  By
           default CPP takes the name of the main input file, deletes any
           directory components and any file suffix such as .c, and appends the
           platform's usual object suffix.  The result is the target.

           An -MT option sets the target to be exactly the string you specify.
           If you want multiple targets, you can specify them as a single
           argument to -MT, or use multiple -MT options.

           For example, -MT '$(objpfx)foo.o' might give

                   $(objpfx)foo.o: foo.c

       -MQ target
           Same as -MT, but it quotes any characters which are special to Make.
           -MQ '$(objpfx)foo.o' gives

                   $$(objpfx)foo.o: foo.c

           The default target is automatically quoted, as if it were given with
           -MQ.

       -MD -MD is equivalent to -M -MF file, except that -E is not implied.  The
           driver determines file based on whether an -o option is given.  If it
           is, the driver uses its argument but with a suffix of .d, otherwise
           it takes the name of the input file, removes any directory components
           and suffix, and applies a .d suffix.

           If -MD is used in conjunction with -E, any -o switch is understood to
           specify the dependency output file, but if used without -E, each -o
           is understood to specify a target object file.

           Since -E is not implied, -MD can be used to generate a dependency
           output file as a side effect of the compilation process.

       -MMD
           Like -MD except mention only user header files, not system header
           files.

       -fpreprocessed
           Indicate to the preprocessor that the input file has already been
           preprocessed.  This suppresses things like macro expansion, trigraph
           conversion, escaped newline splicing, and processing of most
           directives.  The preprocessor still recognizes and removes comments,
           so that you can pass a file preprocessed with -C to the compiler
           without problems.  In this mode the integrated preprocessor is little
           more than a tokenizer for the front ends.

           -fpreprocessed is implicit if the input file has one of the
           extensions .i, .ii or .mi.  These are the extensions that GCC uses
           for preprocessed files created by -save-temps.

       -fdirectives-only
           When preprocessing, handle directives, but do not expand macros.

           The option's behavior depends on the -E and -fpreprocessed options.

           With -E, preprocessing is limited to the handling of directives such
           as "#define", "#ifdef", and "#error".  Other preprocessor operations,
           such as macro expansion and trigraph conversion are not performed.
           In addition, the -dD option is implicitly enabled.

           With -fpreprocessed, predefinition of command line and most builtin
           macros is disabled.  Macros such as "__LINE__", which are
           contextually dependent, are handled normally.  This enables
           compilation of files previously preprocessed with "-E
           -fdirectives-only".

           With both -E and -fpreprocessed, the rules for -fpreprocessed take
           precedence.  This enables full preprocessing of files previously
           preprocessed with "-E -fdirectives-only".

       -fdollars-in-identifiers
           Accept $ in identifiers.

       -fextended-identifiers
           Accept universal character names and extended characters in
           identifiers.  This option is enabled by default for C99 (and later C
           standard versions) and C++.

       -fno-canonical-system-headers
           When preprocessing, do not shorten system header paths with
           canonicalization.

       -fmax-include-depth=depth
           Set the maximum depth of the nested #include. The default is 200.

       -ftabstop=width
           Set the distance between tab stops.  This helps the preprocessor
           report correct column numbers in warnings or errors, even if tabs
           appear on the line.  If the value is less than 1 or greater than 100,
           the option is ignored.  The default is 8.

       -ftrack-macro-expansion[=level]
           Track locations of tokens across macro expansions. This allows the
           compiler to emit diagnostic about the current macro expansion stack
           when a compilation error occurs in a macro expansion. Using this
           option makes the preprocessor and the compiler consume more memory.
           The level parameter can be used to choose the level of precision of
           token location tracking thus decreasing the memory consumption if
           necessary. Value 0 of level de-activates this option. Value 1 tracks
           tokens locations in a degraded mode for the sake of minimal memory
           overhead. In this mode all tokens resulting from the expansion of an
           argument of a function-like macro have the same location. Value 2
           tracks tokens locations completely. This value is the most memory
           hungry.  When this option is given no argument, the default parameter
           value is 2.

           Note that "-ftrack-macro-expansion=2" is activated by default.

       -fmacro-prefix-map=old=new
           When preprocessing files residing in directory old, expand the
           "__FILE__" and "__BASE_FILE__" macros as if the files resided in
           directory new instead.  This can be used to change an absolute path
           to a relative path by using . for new which can result in more
           reproducible builds that are location independent.  This option also
           affects "__builtin_FILE()" during compilation.  See also
           -ffile-prefix-map.

       -fexec-charset=charset
           Set the execution character set, used for string and character
           constants.  The default is UTF-8.  charset can be any encoding
           supported by the system's "iconv" library routine.

       -fwide-exec-charset=charset
           Set the wide execution character set, used for wide string and
           character constants.  The default is UTF-32 or UTF-16, whichever
           corresponds to the width of "wchar_t".  As with -fexec-charset,
           charset can be any encoding supported by the system's "iconv" library
           routine; however, you will have problems with encodings that do not
           fit exactly in "wchar_t".

       -finput-charset=charset
           Set the input character set, used for translation from the character
           set of the input file to the source character set used by GCC.  If
           the locale does not specify, or GCC cannot get this information from
           the locale, the default is UTF-8.  This can be overridden by either
           the locale or this command-line option.  Currently the command-line
           option takes precedence if there's a conflict.  charset can be any
           encoding supported by the system's "iconv" library routine.

       -fpch-deps
           When using precompiled headers, this flag causes the dependency-
           output flags to also list the files from the precompiled header's
           dependencies.  If not specified, only the precompiled header are
           listed and not the files that were used to create it, because those
           files are not consulted when a precompiled header is used.

       -fpch-preprocess
           This option allows use of a precompiled header together with -E.  It
           inserts a special "#pragma", "#pragma GCC pch_preprocess "filename""
           in the output to mark the place where the precompiled header was
           found, and its filename.  When -fpreprocessed is in use, GCC
           recognizes this "#pragma" and loads the PCH.

           This option is off by default, because the resulting preprocessed
           output is only really suitable as input to GCC.  It is switched on by
           -save-temps.

           You should not write this "#pragma" in your own code, but it is safe
           to edit the filename if the PCH file is available in a different
           location.  The filename may be absolute or it may be relative to
           GCC's current directory.

       -fworking-directory
           Enable generation of linemarkers in the preprocessor output that let
           the compiler know the current working directory at the time of
           preprocessing.  When this option is enabled, the preprocessor emits,
           after the initial linemarker, a second linemarker with the current
           working directory followed by two slashes.  GCC uses this directory,
           when it's present in the preprocessed input, as the directory emitted
           as the current working directory in some debugging information
           formats.  This option is implicitly enabled if debugging information
           is enabled, but this can be inhibited with the negated form
           -fno-working-directory.  If the -P flag is present in the command
           line, this option has no effect, since no "#line" directives are
           emitted whatsoever.

       -A predicate=answer
           Make an assertion with the predicate predicate and answer answer.
           This form is preferred to the older form -A predicate(answer), which
           is still supported, because it does not use shell special characters.

       -A -predicate=answer
           Cancel an assertion with the predicate predicate and answer answer.

       -C  Do not discard comments.  All comments are passed through to the
           output file, except for comments in processed directives, which are
           deleted along with the directive.

           You should be prepared for side effects when using -C; it causes the
           preprocessor to treat comments as tokens in their own right.  For
           example, comments appearing at the start of what would be a directive
           line have the effect of turning that line into an ordinary source
           line, since the first token on the line is no longer a #.

       -CC Do not discard comments, including during macro expansion.  This is
           like -C, except that comments contained within macros are also passed
           through to the output file where the macro is expanded.

           In addition to the side effects of the -C option, the -CC option
           causes all C++-style comments inside a macro to be converted to
           C-style comments.  This is to prevent later use of that macro from
           inadvertently commenting out the remainder of the source line.

           The -CC option is generally used to support lint comments.

       -P  Inhibit generation of linemarkers in the output from the
           preprocessor.  This might be useful when running the preprocessor on
           something that is not C code, and will be sent to a program which
           might be confused by the linemarkers.

       -traditional
       -traditional-cpp
           Try to imitate the behavior of pre-standard C preprocessors, as
           opposed to ISO C preprocessors.  See the GNU CPP manual for details.

           Note that GCC does not otherwise attempt to emulate a pre-standard C
           compiler, and these options are only supported with the -E switch, or
           when invoking CPP explicitly.

       -trigraphs
           Support ISO C trigraphs.  These are three-character sequences, all
           starting with ??, that are defined by ISO C to stand for single
           characters.  For example, ??/ stands for \, so '??/n' is a character
           constant for a newline.

           The nine trigraphs and their replacements are

                   Trigraph:       ??(  ??)  ??<  ??>  ??=  ??/  ??'  ??!  ??-
                   Replacement:      [    ]    {    }    #    \    ^    |    ~

           By default, GCC ignores trigraphs, but in standard-conforming modes
           it converts them.  See the -std and -ansi options.

       -remap
           Enable special code to work around file systems which only permit
           very short file names, such as MS-DOS.

       -H  Print the name of each header file used, in addition to other normal
           activities.  Each name is indented to show how deep in the #include
           stack it is.  Precompiled header files are also printed, even if they
           are found to be invalid; an invalid precompiled header file is
           printed with ...x and a valid one with ...! .

       -dletters
           Says to make debugging dumps during compilation as specified by
           letters.  The flags documented here are those relevant to the
           preprocessor.  Other letters are interpreted by the compiler proper,
           or reserved for future versions of GCC, and so are silently ignored.
           If you specify letters whose behavior conflicts, the result is
           undefined.

           -dM Instead of the normal output, generate a list of #define
               directives for all the macros defined during the execution of the
               preprocessor, including predefined macros.  This gives you a way
               of finding out what is predefined in your version of the
               preprocessor.  Assuming you have no file foo.h, the command

                       touch foo.h; cpp -dM foo.h

               shows all the predefined macros.

               If you use -dM without the -E option, -dM is interpreted as a
               synonym for -fdump-rtl-mach.

           -dD Like -dM except in two respects: it does not include the
               predefined macros, and it outputs both the #define directives and
               the result of preprocessing.  Both kinds of output go to the
               standard output file.

           -dN Like -dD, but emit only the macro names, not their expansions.

           -dI Output #include directives in addition to the result of
               preprocessing.

           -dU Like -dD except that only macros that are expanded, or whose
               definedness is tested in preprocessor directives, are output; the
               output is delayed until the use or test of the macro; and #undef
               directives are also output for macros tested but undefined at the
               time.

       -fdebug-cpp
           This option is only useful for debugging GCC.  When used from CPP or
           with -E, it dumps debugging information about location maps.  Every
           token in the output is preceded by the dump of the map its location
           belongs to.

           When used from GCC without -E, this option has no effect.

       -Wp,option
           You can use -Wp,option to bypass the compiler driver and pass option
           directly through to the preprocessor.  If option contains commas, it
           is split into multiple options at the commas.  However, many options
           are modified, translated or interpreted by the compiler driver before
           being passed to the preprocessor, and -Wp forcibly bypasses this
           phase.  The preprocessor's direct interface is undocumented and
           subject to change, so whenever possible you should avoid using -Wp
           and let the driver handle the options instead.

       -Xpreprocessor option
           Pass option as an option to the preprocessor.  You can use this to
           supply system-specific preprocessor options that GCC does not
           recognize.

           If you want to pass an option that takes an argument, you must use
           -Xpreprocessor twice, once for the option and once for the argument.

       -no-integrated-cpp
           Perform preprocessing as a separate pass before compilation.  By
           default, GCC performs preprocessing as an integrated part of input
           tokenization and parsing.  If this option is provided, the
           appropriate language front end (cc1, cc1plus, or cc1obj for C, C++,
           and Objective-C, respectively) is instead invoked twice, once for
           preprocessing only and once for actual compilation of the
           preprocessed input.  This option may be useful in conjunction with
           the -B or -wrapper options to specify an alternate preprocessor or
           perform additional processing of the program source between normal
           preprocessing and compilation.

       -flarge-source-files
           Adjust GCC to expect large source files, at the expense of slower
           compilation and higher memory usage.

           Specifically, GCC normally tracks both column numbers and line
           numbers within source files and it normally prints both of these
           numbers in diagnostics.  However, once it has processed a certain
           number of source lines, it stops tracking column numbers and only
           tracks line numbers.  This means that diagnostics for later lines do
           not include column numbers.  It also means that options like
           -Wmisleading-indentation cease to work at that point, although the
           compiler prints a note if this happens.  Passing -flarge-source-files
           significantly increases the number of source lines that GCC can
           process before it stops tracking columns.

   Passing Options to the Assembler
       You can pass options to the assembler.

       -Wa,option
           Pass option as an option to the assembler.  If option contains
           commas, it is split into multiple options at the commas.

       -Xassembler option
           Pass option as an option to the assembler.  You can use this to
           supply system-specific assembler options that GCC does not recognize.

           If you want to pass an option that takes an argument, you must use
           -Xassembler twice, once for the option and once for the argument.

   Options for Linking
       These options come into play when the compiler links object files into an
       executable output file.  They are meaningless if the compiler is not
       doing a link step.

       object-file-name
           A file name that does not end in a special recognized suffix is
           considered to name an object file or library.  (Object files are
           distinguished from libraries by the linker according to the file
           contents.)  If linking is done, these object files are used as input
           to the linker.

       -c
       -S
       -E  If any of these options is used, then the linker is not run, and
           object file names should not be used as arguments.

       -flinker-output=type
           This option controls code generation of the link-time optimizer.  By
           default the linker output is automatically determined by the linker
           plugin.  For debugging the compiler and if incremental linking with a
           non-LTO object file is desired, it may be useful to control the type
           manually.

           If type is exec, code generation produces a static binary. In this
           case -fpic and -fpie are both disabled.

           If type is dyn, code generation produces a shared library.  In this
           case -fpic or -fPIC is preserved, but not enabled automatically.
           This allows to build shared libraries without position-independent
           code on architectures where this is possible, i.e. on x86.

           If type is pie, code generation produces an -fpie executable. This
           results in similar optimizations as exec except that -fpie is not
           disabled if specified at compilation time.

           If type is rel, the compiler assumes that incremental linking is
           done.  The sections containing intermediate code for link-time
           optimization are merged, pre-optimized, and output to the resulting
           object file. In addition, if -ffat-lto-objects is specified, binary
           code is produced for future non-LTO linking. The object file produced
           by incremental linking is smaller than a static library produced from
           the same object files.  At link time the result of incremental
           linking also loads faster than a static library assuming that the
           majority of objects in the library are used.

           Finally nolto-rel configures the compiler for incremental linking
           where code generation is forced, a final binary is produced, and the
           intermediate code for later link-time optimization is stripped. When
           multiple object files are linked together the resulting code is
           better optimized than with link-time optimizations disabled (for
           example, cross-module inlining happens), but most of benefits of
           whole program optimizations are lost.

           During the incremental link (by -r) the linker plugin defaults to
           rel. With current interfaces to GNU Binutils it is however not
           possible to incrementally link LTO objects and non-LTO objects into a
           single mixed object file.  If any of object files in incremental link
           cannot be used for link-time optimization, the linker plugin issues a
           warning and uses nolto-rel. To maintain whole program optimization,
           it is recommended to link such objects into static library instead.
           Alternatively it is possible to use H.J. Lu's binutils with support
           for mixed objects.

       -fuse-ld=bfd
           Use the bfd linker instead of the default linker.

       -fuse-ld=gold
           Use the gold linker instead of the default linker.

       -fuse-ld=lld
           Use the LLVM lld linker instead of the default linker.

       -llibrary
       -l library
           Search the library named library when linking.  (The second
           alternative with the library as a separate argument is only for POSIX
           compliance and is not recommended.)

           The -l option is passed directly to the linker by GCC.  Refer to your
           linker documentation for exact details.  The general description
           below applies to the GNU linker.

           The linker searches a standard list of directories for the library.
           The directories searched include several standard system directories
           plus any that you specify with -L.

           Static libraries are archives of object files, and have file names
           like liblibrary.a.  Some targets also support shared libraries, which
           typically have names like liblibrary.so.  If both static and shared
           libraries are found, the linker gives preference to linking with the
           shared library unless the -static option is used.

           It makes a difference where in the command you write this option; the
           linker searches and processes libraries and object files in the order
           they are specified.  Thus, foo.o -lz bar.o searches library z after
           file foo.o but before bar.o.  If bar.o refers to functions in z,
           those functions may not be loaded.

       -lobjc
           You need this special case of the -l option in order to link an
           Objective-C or Objective-C++ program.

       -nostartfiles
           Do not use the standard system startup files when linking.  The
           standard system libraries are used normally, unless -nostdlib,
           -nolibc, or -nodefaultlibs is used.

       -nodefaultlibs
           Do not use the standard system libraries when linking.  Only the
           libraries you specify are passed to the linker, and options
           specifying linkage of the system libraries, such as -static-libgcc or
           -shared-libgcc, are ignored.  The standard startup files are used
           normally, unless -nostartfiles is used.

           The compiler may generate calls to "memcmp", "memset", "memcpy" and
           "memmove".  These entries are usually resolved by entries in libc.
           These entry points should be supplied through some other mechanism
           when this option is specified.

       -nolibc
           Do not use the C library or system libraries tightly coupled with it
           when linking.  Still link with the startup files, libgcc or toolchain
           provided language support libraries such as libgnat, libgfortran or
           libstdc++ unless options preventing their inclusion are used as well.
           This typically removes -lc from the link command line, as well as
           system libraries that normally go with it and become meaningless when
           absence of a C library is assumed, for example -lpthread or -lm in
           some configurations.  This is intended for bare-board targets when
           there is indeed no C library available.

       -nostdlib
           Do not use the standard system startup files or libraries when
           linking.  No startup files and only the libraries you specify are
           passed to the linker, and options specifying linkage of the system
           libraries, such as -static-libgcc or -shared-libgcc, are ignored.

           The compiler may generate calls to "memcmp", "memset", "memcpy" and
           "memmove".  These entries are usually resolved by entries in libc.
           These entry points should be supplied through some other mechanism
           when this option is specified.

           One of the standard libraries bypassed by -nostdlib and
           -nodefaultlibs is libgcc.a, a library of internal subroutines which
           GCC uses to overcome shortcomings of particular machines, or special
           needs for some languages.

           In most cases, you need libgcc.a even when you want to avoid other
           standard libraries.  In other words, when you specify -nostdlib or
           -nodefaultlibs you should usually specify -lgcc as well.  This
           ensures that you have no unresolved references to internal GCC
           library subroutines.  (An example of such an internal subroutine is
           "__main", used to ensure C++ constructors are called.)

       -e entry
       --entry=entry
           Specify that the program entry point is entry.  The argument is
           interpreted by the linker; the GNU linker accepts either a symbol
           name or an address.

       -pie
           Produce a dynamically linked position independent executable on
           targets that support it.  For predictable results, you must also
           specify the same set of options used for compilation (-fpie, -fPIE,
           or model suboptions) when you specify this linker option.

       -no-pie
           Don't produce a dynamically linked position independent executable.

       -static-pie
           Produce a static position independent executable on targets that
           support it.  A static position independent executable is similar to a
           static executable, but can be loaded at any address without a dynamic
           linker.  For predictable results, you must also specify the same set
           of options used for compilation (-fpie, -fPIE, or model suboptions)
           when you specify this linker option.

       -pthread
           Link with the POSIX threads library.  This option is supported on
           GNU/Linux targets, most other Unix derivatives, and also on x86
           Cygwin and MinGW targets.  On some targets this option also sets
           flags for the preprocessor, so it should be used consistently for
           both compilation and linking.

       -r  Produce a relocatable object as output.  This is also known as
           partial linking.

       -rdynamic
           Pass the flag -export-dynamic to the ELF linker, on targets that
           support it. This instructs the linker to add all symbols, not only
           used ones, to the dynamic symbol table. This option is needed for
           some uses of "dlopen" or to allow obtaining backtraces from within a
           program.

       -s  Remove all symbol table and relocation information from the
           executable.

       -static
           On systems that support dynamic linking, this overrides -pie and
           prevents linking with the shared libraries.  On other systems, this
           option has no effect.

       -shared
           Produce a shared object which can then be linked with other objects
           to form an executable.  Not all systems support this option.  For
           predictable results, you must also specify the same set of options
           used for compilation (-fpic, -fPIC, or model suboptions) when you
           specify this linker option.[1]

       -shared-libgcc
       -static-libgcc
           On systems that provide libgcc as a shared library, these options
           force the use of either the shared or static version, respectively.
           If no shared version of libgcc was built when the compiler was
           configured, these options have no effect.

           There are several situations in which an application should use the
           shared libgcc instead of the static version.  The most common of
           these is when the application wishes to throw and catch exceptions
           across different shared libraries.  In that case, each of the
           libraries as well as the application itself should use the shared
           libgcc.

           Therefore, the G++ driver automatically adds -shared-libgcc whenever
           you build a shared library or a main executable, because C++ programs
           typically use exceptions, so this is the right thing to do.

           If, instead, you use the GCC driver to create shared libraries, you
           may find that they are not always linked with the shared libgcc.  If
           GCC finds, at its configuration time, that you have a non-GNU linker
           or a GNU linker that does not support option --eh-frame-hdr, it links
           the shared version of libgcc into shared libraries by default.
           Otherwise, it takes advantage of the linker and optimizes away the
           linking with the shared version of libgcc, linking with the static
           version of libgcc by default.  This allows exceptions to propagate
           through such shared libraries, without incurring relocation costs at
           library load time.

           However, if a library or main executable is supposed to throw or
           catch exceptions, you must link it using the G++ driver, or using the
           option -shared-libgcc, such that it is linked with the shared libgcc.

       -static-libasan
           When the -fsanitize=address option is used to link a program, the GCC
           driver automatically links against libasan.  If libasan is available
           as a shared library, and the -static option is not used, then this
           links against the shared version of libasan.  The -static-libasan
           option directs the GCC driver to link libasan statically, without
           necessarily linking other libraries statically.

       -static-libtsan
           When the -fsanitize=thread option is used to link a program, the GCC
           driver automatically links against libtsan.  If libtsan is available
           as a shared library, and the -static option is not used, then this
           links against the shared version of libtsan.  The -static-libtsan
           option directs the GCC driver to link libtsan statically, without
           necessarily linking other libraries statically.

       -static-liblsan
           When the -fsanitize=leak option is used to link a program, the GCC
           driver automatically links against liblsan.  If liblsan is available
           as a shared library, and the -static option is not used, then this
           links against the shared version of liblsan.  The -static-liblsan
           option directs the GCC driver to link liblsan statically, without
           necessarily linking other libraries statically.

       -static-libubsan
           When the -fsanitize=undefined option is used to link a program, the
           GCC driver automatically links against libubsan.  If libubsan is
           available as a shared library, and the -static option is not used,
           then this links against the shared version of libubsan.  The
           -static-libubsan option directs the GCC driver to link libubsan
           statically, without necessarily linking other libraries statically.

       -static-libstdc++
           When the g++ program is used to link a C++ program, it normally
           automatically links against libstdc++.  If libstdc++ is available as
           a shared library, and the -static option is not used, then this links
           against the shared version of libstdc++.  That is normally fine.
           However, it is sometimes useful to freeze the version of libstdc++
           used by the program without going all the way to a fully static link.
           The -static-libstdc++ option directs the g++ driver to link libstdc++
           statically, without necessarily linking other libraries statically.

       -symbolic
           Bind references to global symbols when building a shared object.
           Warn about any unresolved references (unless overridden by the link
           editor option -Xlinker -z -Xlinker defs).  Only a few systems support
           this option.

       -T script
           Use script as the linker script.  This option is supported by most
           systems using the GNU linker.  On some targets, such as bare-board
           targets without an operating system, the -T option may be required
           when linking to avoid references to undefined symbols.

       -Xlinker option
           Pass option as an option to the linker.  You can use this to supply
           system-specific linker options that GCC does not recognize.

           If you want to pass an option that takes a separate argument, you
           must use -Xlinker twice, once for the option and once for the
           argument.  For example, to pass -assert definitions, you must write
           -Xlinker -assert -Xlinker definitions.  It does not work to write
           -Xlinker "-assert definitions", because this passes the entire string
           as a single argument, which is not what the linker expects.

           When using the GNU linker, it is usually more convenient to pass
           arguments to linker options using the option=value syntax than as
           separate arguments.  For example, you can specify -Xlinker
           -Map=output.map rather than -Xlinker -Map -Xlinker output.map.  Other
           linkers may not support this syntax for command-line options.

       -Wl,option
           Pass option as an option to the linker.  If option contains commas,
           it is split into multiple options at the commas.  You can use this
           syntax to pass an argument to the option.  For example,
           -Wl,-Map,output.map passes -Map output.map to the linker.  When using
           the GNU linker, you can also get the same effect with
           -Wl,-Map=output.map.

       -u symbol
           Pretend the symbol symbol is undefined, to force linking of library
           modules to define it.  You can use -u multiple times with different
           symbols to force loading of additional library modules.

       -z keyword
           -z is passed directly on to the linker along with the keyword
           keyword. See the section in the documentation of your linker for
           permitted values and their meanings.

   Options for Directory Search
       These options specify directories to search for header files, for
       libraries and for parts of the compiler:

       -I dir
       -iquote dir
       -isystem dir
       -idirafter dir
           Add the directory dir to the list of directories to be searched for
           header files during preprocessing.  If dir begins with = or $SYSROOT,
           then the = or $SYSROOT is replaced by the sysroot prefix; see
           --sysroot and -isysroot.

           Directories specified with -iquote apply only to the quote form of
           the directive, "#include "file"".  Directories specified with -I,
           -isystem, or -idirafter apply to lookup for both the
           "#include "file"" and "#include <file>" directives.

           You can specify any number or combination of these options on the
           command line to search for header files in several directories.  The
           lookup order is as follows:

           1.  For the quote form of the include directive, the directory of the
               current file is searched first.

           2.  For the quote form of the include directive, the directories
               specified by -iquote options are searched in left-to-right order,
               as they appear on the command line.

           3.  Directories specified with -I options are scanned in left-to-
               right order.

           4.  Directories specified with -isystem options are scanned in left-
               to-right order.

           5.  Standard system directories are scanned.

           6.  Directories specified with -idirafter options are scanned in
               left-to-right order.

           You can use -I to override a system header file, substituting your
           own version, since these directories are searched before the standard
           system header file directories.  However, you should not use this
           option to add directories that contain vendor-supplied system header
           files; use -isystem for that.

           The -isystem and -idirafter options also mark the directory as a
           system directory, so that it gets the same special treatment that is
           applied to the standard system directories.

           If a standard system include directory, or a directory specified with
           -isystem, is also specified with -I, the -I option is ignored.  The
           directory is still searched but as a system directory at its normal
           position in the system include chain.  This is to ensure that GCC's
           procedure to fix buggy system headers and the ordering for the
           "#include_next" directive are not inadvertently changed.  If you
           really need to change the search order for system directories, use
           the -nostdinc and/or -isystem options.

       -I- Split the include path.  This option has been deprecated.  Please use
           -iquote instead for -I directories before the -I- and remove the -I-
           option.

           Any directories specified with -I options before -I- are searched
           only for headers requested with "#include "file""; they are not
           searched for "#include <file>".  If additional directories are
           specified with -I options after the -I-, those directories are
           searched for all #include directives.

           In addition, -I- inhibits the use of the directory of the current
           file directory as the first search directory for "#include "file"".
           There is no way to override this effect of -I-.

       -iprefix prefix
           Specify prefix as the prefix for subsequent -iwithprefix options.  If
           the prefix represents a directory, you should include the final /.

       -iwithprefix dir
       -iwithprefixbefore dir
           Append dir to the prefix specified previously with -iprefix, and add
           the resulting directory to the include search path.
           -iwithprefixbefore puts it in the same place -I would; -iwithprefix
           puts it where -idirafter would.

       -isysroot dir
           This option is like the --sysroot option, but applies only to header
           files (except for Darwin targets, where it applies to both header
           files and libraries).  See the --sysroot option for more information.

       -imultilib dir
           Use dir as a subdirectory of the directory containing target-specific
           C++ headers.

       -nostdinc
           Do not search the standard system directories for header files.  Only
           the directories explicitly specified with -I, -iquote, -isystem,
           and/or -idirafter options (and the directory of the current file, if
           appropriate) are searched.

       -nostdinc++
           Do not search for header files in the C++-specific standard
           directories, but do still search the other standard directories.
           (This option is used when building the C++ library.)

       -iplugindir=dir
           Set the directory to search for plugins that are passed by
           -fplugin=name instead of -fplugin=path/name.so.  This option is not
           meant to be used by the user, but only passed by the driver.

       -Ldir
           Add directory dir to the list of directories to be searched for -l.

       -Bprefix
           This option specifies where to find the executables, libraries,
           include files, and data files of the compiler itself.

           The compiler driver program runs one or more of the subprograms cpp,
           cc1, as and ld.  It tries prefix as a prefix for each program it
           tries to run, both with and without machine/version/ for the
           corresponding target machine and compiler version.

           For each subprogram to be run, the compiler driver first tries the -B
           prefix, if any.  If that name is not found, or if -B is not
           specified, the driver tries two standard prefixes, /usr/lib/gcc/ and
           /usr/local/lib/gcc/.  If neither of those results in a file name that
           is found, the unmodified program name is searched for using the
           directories specified in your PATH environment variable.

           The compiler checks to see if the path provided by -B refers to a
           directory, and if necessary it adds a directory separator character
           at the end of the path.

           -B prefixes that effectively specify directory names also apply to
           libraries in the linker, because the compiler translates these
           options into -L options for the linker.  They also apply to include
           files in the preprocessor, because the compiler translates these
           options into -isystem options for the preprocessor.  In this case,
           the compiler appends include to the prefix.

           The runtime support file libgcc.a can also be searched for using the
           -B prefix, if needed.  If it is not found there, the two standard
           prefixes above are tried, and that is all.  The file is left out of
           the link if it is not found by those means.

           Another way to specify a prefix much like the -B prefix is to use the
           environment variable GCC_EXEC_PREFIX.

           As a special kludge, if the path provided by -B is [dir/]stageN/,
           where N is a number in the range 0 to 9, then it is replaced by
           [dir/]include.  This is to help with boot-strapping the compiler.

       -no-canonical-prefixes
           Do not expand any symbolic links, resolve references to /../ or /./,
           or make the path absolute when generating a relative prefix.

       --sysroot=dir
           Use dir as the logical root directory for headers and libraries.  For
           example, if the compiler normally searches for headers in
           /usr/include and libraries in /usr/lib, it instead searches
           dir/usr/include and dir/usr/lib.

           If you use both this option and the -isysroot option, then the
           --sysroot option applies to libraries, but the -isysroot option
           applies to header files.

           The GNU linker (beginning with version 2.16) has the necessary
           support for this option.  If your linker does not support this
           option, the header file aspect of --sysroot still works, but the
           library aspect does not.

       --no-sysroot-suffix
           For some targets, a suffix is added to the root directory specified
           with --sysroot, depending on the other options used, so that headers
           may for example be found in dir/suffix/usr/include instead of
           dir/usr/include.  This option disables the addition of such a suffix.

   Options for Code Generation Conventions
       These machine-independent options control the interface conventions used
       in code generation.

       Most of them have both positive and negative forms; the negative form of
       -ffoo is -fno-foo.  In the table below, only one of the forms is
       listed---the one that is not the default.  You can figure out the other
       form by either removing no- or adding it.

       -fstack-reuse=reuse-level
           This option controls stack space reuse for user declared local/auto
           variables and compiler generated temporaries.  reuse_level can be
           all, named_vars, or none. all enables stack reuse for all local
           variables and temporaries, named_vars enables the reuse only for user
           defined local variables with names, and none disables stack reuse
           completely. The default value is all. The option is needed when the
           program extends the lifetime of a scoped local variable or a compiler
           generated temporary beyond the end point defined by the language.
           When a lifetime of a variable ends, and if the variable lives in
           memory, the optimizing compiler has the freedom to reuse its stack
           space with other temporaries or scoped local variables whose live
           range does not overlap with it. Legacy code extending local lifetime
           is likely to break with the stack reuse optimization.

           For example,

                      int *p;
                      {
                        int local1;

                        p = &local1;
                        local1 = 10;
                        ....
                      }
                      {
                         int local2;
                         local2 = 20;
                         ...
                      }

                      if (*p == 10)  // out of scope use of local1
                        {

                        }

           Another example:

                      struct A
                      {
                          A(int k) : i(k), j(k) { }
                          int i;
                          int j;
                      };

                      A *ap;

                      void foo(const A& ar)
                      {
                         ap = &ar;
                      }

                      void bar()
                      {
                         foo(A(10)); // temp object's lifetime ends when foo returns

                         {
                           A a(20);
                           ....
                         }
                         ap->i+= 10;  // ap references out of scope temp whose space
                                      // is reused with a. What is the value of ap->i?
                      }

           The lifetime of a compiler generated temporary is well defined by the
           C++ standard. When a lifetime of a temporary ends, and if the
           temporary lives in memory, the optimizing compiler has the freedom to
           reuse its stack space with other temporaries or scoped local
           variables whose live range does not overlap with it. However some of
           the legacy code relies on the behavior of older compilers in which
           temporaries' stack space is not reused, the aggressive stack reuse
           can lead to runtime errors. This option is used to control the
           temporary stack reuse optimization.

       -ftrapv
           This option generates traps for signed overflow on addition,
           subtraction, multiplication operations.  The options -ftrapv and
           -fwrapv override each other, so using -ftrapv -fwrapv on the command-
           line results in -fwrapv being effective.  Note that only active
           options override, so using -ftrapv -fwrapv -fno-wrapv on the command-
           line results in -ftrapv being effective.

       -fwrapv
           This option instructs the compiler to assume that signed arithmetic
           overflow of addition, subtraction and multiplication wraps around
           using twos-complement representation.  This flag enables some
           optimizations and disables others.  The options -ftrapv and -fwrapv
           override each other, so using -ftrapv -fwrapv on the command-line
           results in -fwrapv being effective.  Note that only active options
           override, so using -ftrapv -fwrapv -fno-wrapv on the command-line
           results in -ftrapv being effective.

       -fwrapv-pointer
           This option instructs the compiler to assume that pointer arithmetic
           overflow on addition and subtraction wraps around using twos-
           complement representation.  This flag disables some optimizations
           which assume pointer overflow is invalid.

       -fstrict-overflow
           This option implies -fno-wrapv -fno-wrapv-pointer and when negated
           implies -fwrapv -fwrapv-pointer.

       -fexceptions
           Enable exception handling.  Generates extra code needed to propagate
           exceptions.  For some targets, this implies GCC generates frame
           unwind information for all functions, which can produce significant
           data size overhead, although it does not affect execution.  If you do
           not specify this option, GCC enables it by default for languages like
           C++ that normally require exception handling, and disables it for
           languages like C that do not normally require it.  However, you may
           need to enable this option when compiling C code that needs to
           interoperate properly with exception handlers written in C++.  You
           may also wish to disable this option if you are compiling older C++
           programs that don't use exception handling.

       -fnon-call-exceptions
           Generate code that allows trapping instructions to throw exceptions.
           Note that this requires platform-specific runtime support that does
           not exist everywhere.  Moreover, it only allows trapping instructions
           to throw exceptions, i.e. memory references or floating-point
           instructions.  It does not allow exceptions to be thrown from
           arbitrary signal handlers such as "SIGALRM".

       -fdelete-dead-exceptions
           Consider that instructions that may throw exceptions but don't
           otherwise contribute to the execution of the program can be optimized
           away.  This option is enabled by default for the Ada compiler, as
           permitted by the Ada language specification.  Optimization passes
           that cause dead exceptions to be removed are enabled independently at
           different optimization levels.

       -funwind-tables
           Similar to -fexceptions, except that it just generates any needed
           static data, but does not affect the generated code in any other way.
           You normally do not need to enable this option; instead, a language
           processor that needs this handling enables it on your behalf.

       -fasynchronous-unwind-tables
           Generate unwind table in DWARF format, if supported by target
           machine.  The table is exact at each instruction boundary, so it can
           be used for stack unwinding from asynchronous events (such as
           debugger or garbage collector).

       -fno-gnu-unique
           On systems with recent GNU assembler and C library, the C++ compiler
           uses the "STB_GNU_UNIQUE" binding to make sure that definitions of
           template static data members and static local variables in inline
           functions are unique even in the presence of "RTLD_LOCAL"; this is
           necessary to avoid problems with a library used by two different
           "RTLD_LOCAL" plugins depending on a definition in one of them and
           therefore disagreeing with the other one about the binding of the
           symbol.  But this causes "dlclose" to be ignored for affected DSOs;
           if your program relies on reinitialization of a DSO via "dlclose" and
           "dlopen", you can use -fno-gnu-unique.

       -fpcc-struct-return
           Return "short" "struct" and "union" values in memory like longer
           ones, rather than in registers.  This convention is less efficient,
           but it has the advantage of allowing intercallability between GCC-
           compiled files and files compiled with other compilers, particularly
           the Portable C Compiler (pcc).

           The precise convention for returning structures in memory depends on
           the target configuration macros.

           Short structures and unions are those whose size and alignment match
           that of some integer type.

           Warning: code compiled with the -fpcc-struct-return switch is not
           binary compatible with code compiled with the -freg-struct-return
           switch.  Use it to conform to a non-default application binary
           interface.

       -freg-struct-return
           Return "struct" and "union" values in registers when possible.  This
           is more efficient for small structures than -fpcc-struct-return.

           If you specify neither -fpcc-struct-return nor -freg-struct-return,
           GCC defaults to whichever convention is standard for the target.  If
           there is no standard convention, GCC defaults to -fpcc-struct-return,
           except on targets where GCC is the principal compiler.  In those
           cases, we can choose the standard, and we chose the more efficient
           register return alternative.

           Warning: code compiled with the -freg-struct-return switch is not
           binary compatible with code compiled with the -fpcc-struct-return
           switch.  Use it to conform to a non-default application binary
           interface.

       -fshort-enums
           Allocate to an "enum" type only as many bytes as it needs for the
           declared range of possible values.  Specifically, the "enum" type is
           equivalent to the smallest integer type that has enough room.

           Warning: the -fshort-enums switch causes GCC to generate code that is
           not binary compatible with code generated without that switch.  Use
           it to conform to a non-default application binary interface.

       -fshort-wchar
           Override the underlying type for "wchar_t" to be "short unsigned int"
           instead of the default for the target.  This option is useful for
           building programs to run under WINE.

           Warning: the -fshort-wchar switch causes GCC to generate code that is
           not binary compatible with code generated without that switch.  Use
           it to conform to a non-default application binary interface.

       -fcommon
           In C code, this option controls the placement of global variables
           defined without an initializer, known as tentative definitions in the
           C standard.  Tentative definitions are distinct from declarations of
           a variable with the "extern" keyword, which do not allocate storage.

           The default is -fno-common, which specifies that the compiler places
           uninitialized global variables in the BSS section of the object file.
           This inhibits the merging of tentative definitions by the linker so
           you get a multiple-definition error if the same variable is
           accidentally defined in more than one compilation unit.

           The -fcommon places uninitialized global variables in a common block.
           This allows the linker to resolve all tentative definitions of the
           same variable in different compilation units to the same object, or
           to a non-tentative definition.  This behavior is inconsistent with
           C++, and on many targets implies a speed and code size penalty on
           global variable references.  It is mainly useful to enable legacy
           code to link without errors.

       -fno-ident
           Ignore the "#ident" directive.

       -finhibit-size-directive
           Don't output a ".size" assembler directive, or anything else that
           would cause trouble if the function is split in the middle, and the
           two halves are placed at locations far apart in memory.  This option
           is used when compiling crtstuff.c; you should not need to use it for
           anything else.

       -fverbose-asm
           Put extra commentary information in the generated assembly code to
           make it more readable.  This option is generally only of use to those
           who actually need to read the generated assembly code (perhaps while
           debugging the compiler itself).

           -fno-verbose-asm, the default, causes the extra information to be
           omitted and is useful when comparing two assembler files.

           The added comments include:

           *   information on the compiler version and command-line options,

           *   the source code lines associated with the assembly instructions,
               in the form FILENAME:LINENUMBER:CONTENT OF LINE,

           *   hints on which high-level expressions correspond to the various
               assembly instruction operands.

           For example, given this C source file:

                   int test (int n)
                   {
                     int i;
                     int total = 0;

                     for (i = 0; i < n; i++)
                       total += i * i;

                     return total;
                   }

           compiling to (x86_64) assembly via -S and emitting the result direct
           to stdout via -o -

                   gcc -S test.c -fverbose-asm -Os -o -

           gives output similar to this:

                           .file   "test.c"
                   # GNU C11 (GCC) version 7.0.0 20160809 (experimental) (x86_64-pc-linux-gnu)
                     [...snip...]
                   # options passed:
                     [...snip...]

                           .text
                           .globl  test
                           .type   test, @function
                   test:
                   .LFB0:
                           .cfi_startproc
                   # test.c:4:   int total = 0;
                           xorl    %eax, %eax      # <retval>
                   # test.c:6:   for (i = 0; i < n; i++)
                           xorl    %edx, %edx      # i
                   .L2:
                   # test.c:6:   for (i = 0; i < n; i++)
                           cmpl    %edi, %edx      # n, i
                           jge     .L5     #,
                   # test.c:7:     total += i * i;
                           movl    %edx, %ecx      # i, tmp92
                           imull   %edx, %ecx      # i, tmp92
                   # test.c:6:   for (i = 0; i < n; i++)
                           incl    %edx    # i
                   # test.c:7:     total += i * i;
                           addl    %ecx, %eax      # tmp92, <retval>
                           jmp     .L2     #
                   .L5:
                   # test.c:10: }
                           ret
                           .cfi_endproc
                   .LFE0:
                           .size   test, .-test
                           .ident  "GCC: (GNU) 7.0.0 20160809 (experimental)"
                           .section        .note.GNU-stack,"",@progbits

           The comments are intended for humans rather than machines and hence
           the precise format of the comments is subject to change.

       -frecord-gcc-switches
           This switch causes the command line used to invoke the compiler to be
           recorded into the object file that is being created.  This switch is
           only implemented on some targets and the exact format of the
           recording is target and binary file format dependent, but it usually
           takes the form of a section containing ASCII text.  This switch is
           related to the -fverbose-asm switch, but that switch only records
           information in the assembler output file as comments, so it never
           reaches the object file.  See also -grecord-gcc-switches for another
           way of storing compiler options into the object file.

       -fpic
           Generate position-independent code (PIC) suitable for use in a shared
           library, if supported for the target machine.  Such code accesses all
           constant addresses through a global offset table (GOT).  The dynamic
           loader resolves the GOT entries when the program starts (the dynamic
           loader is not part of GCC; it is part of the operating system).  If
           the GOT size for the linked executable exceeds a machine-specific
           maximum size, you get an error message from the linker indicating
           that -fpic does not work; in that case, recompile with -fPIC instead.
           (These maximums are 8k on the SPARC, 28k on AArch64 and 32k on the
           m68k and RS/6000.  The x86 has no such limit.)

           Position-independent code requires special support, and therefore
           works only on certain machines.  For the x86, GCC supports PIC for
           System V but not for the Sun 386i.  Code generated for the IBM
           RS/6000 is always position-independent.

           When this flag is set, the macros "__pic__" and "__PIC__" are defined
           to 1.

       -fPIC
           If supported for the target machine, emit position-independent code,
           suitable for dynamic linking and avoiding any limit on the size of
           the global offset table.  This option makes a difference on AArch64,
           m68k, PowerPC and SPARC.

           Position-independent code requires special support, and therefore
           works only on certain machines.

           When this flag is set, the macros "__pic__" and "__PIC__" are defined
           to 2.

       -fpie
       -fPIE
           These options are similar to -fpic and -fPIC, but the generated
           position-independent code can be only linked into executables.
           Usually these options are used to compile code that will be linked
           using the -pie GCC option.

           -fpie and -fPIE both define the macros "__pie__" and "__PIE__".  The
           macros have the value 1 for -fpie and 2 for -fPIE.

       -fno-plt
           Do not use the PLT for external function calls in position-
           independent code.  Instead, load the callee address at call sites
           from the GOT and branch to it.  This leads to more efficient code by
           eliminating PLT stubs and exposing GOT loads to optimizations.  On
           architectures such as 32-bit x86 where PLT stubs expect the GOT
           pointer in a specific register, this gives more register allocation
           freedom to the compiler.  Lazy binding requires use of the PLT; with
           -fno-plt all external symbols are resolved at load time.

           Alternatively, the function attribute "noplt" can be used to avoid
           calls through the PLT for specific external functions.

           In position-dependent code, a few targets also convert calls to
           functions that are marked to not use the PLT to use the GOT instead.

       -fno-jump-tables
           Do not use jump tables for switch statements even where it would be
           more efficient than other code generation strategies.  This option is
           of use in conjunction with -fpic or -fPIC for building code that
           forms part of a dynamic linker and cannot reference the address of a
           jump table.  On some targets, jump tables do not require a GOT and
           this option is not needed.

       -fno-bit-tests
           Do not use bit tests for switch statements even where it would be
           more efficient than other code generation strategies.

       -ffixed-reg
           Treat the register named reg as a fixed register; generated code
           should never refer to it (except perhaps as a stack pointer, frame
           pointer or in some other fixed role).

           reg must be the name of a register.  The register names accepted are
           machine-specific and are defined in the "REGISTER_NAMES" macro in the
           machine description macro file.

           This flag does not have a negative form, because it specifies a
           three-way choice.

       -fcall-used-reg
           Treat the register named reg as an allocable register that is
           clobbered by function calls.  It may be allocated for temporaries or
           variables that do not live across a call.  Functions compiled this
           way do not save and restore the register reg.

           It is an error to use this flag with the frame pointer or stack
           pointer.  Use of this flag for other registers that have fixed
           pervasive roles in the machine's execution model produces disastrous
           results.

           This flag does not have a negative form, because it specifies a
           three-way choice.

       -fcall-saved-reg
           Treat the register named reg as an allocable register saved by
           functions.  It may be allocated even for temporaries or variables
           that live across a call.  Functions compiled this way save and
           restore the register reg if they use it.

           It is an error to use this flag with the frame pointer or stack
           pointer.  Use of this flag for other registers that have fixed
           pervasive roles in the machine's execution model produces disastrous
           results.

           A different sort of disaster results from the use of this flag for a
           register in which function values may be returned.

           This flag does not have a negative form, because it specifies a
           three-way choice.

       -fpack-struct[=n]
           Without a value specified, pack all structure members together
           without holes.  When a value is specified (which must be a small
           power of two), pack structure members according to this value,
           representing the maximum alignment (that is, objects with default
           alignment requirements larger than this are output potentially
           unaligned at the next fitting location.

           Warning: the -fpack-struct switch causes GCC to generate code that is
           not binary compatible with code generated without that switch.
           Additionally, it makes the code suboptimal.  Use it to conform to a
           non-default application binary interface.

       -fleading-underscore
           This option and its counterpart, -fno-leading-underscore, forcibly
           change the way C symbols are represented in the object file.  One use
           is to help link with legacy assembly code.

           Warning: the -fleading-underscore switch causes GCC to generate code
           that is not binary compatible with code generated without that
           switch.  Use it to conform to a non-default application binary
           interface.  Not all targets provide complete support for this switch.

       -ftls-model=model
           Alter the thread-local storage model to be used.  The model argument
           should be one of global-dynamic, local-dynamic, initial-exec or
           local-exec.  Note that the choice is subject to optimization: the
           compiler may use a more efficient model for symbols not visible
           outside of the translation unit, or if -fpic is not given on the
           command line.

           The default without -fpic is initial-exec; with -fpic the default is
           global-dynamic.

       -ftrampolines
           For targets that normally need trampolines for nested functions,
           always generate them instead of using descriptors.  Otherwise, for
           targets that do not need them, like for example HP-PA or IA-64, do
           nothing.

           A trampoline is a small piece of code that is created at run time on
           the stack when the address of a nested function is taken, and is used
           to call the nested function indirectly.  Therefore, it requires the
           stack to be made executable in order for the program to work
           properly.

           -fno-trampolines is enabled by default on a language by language
           basis to let the compiler avoid generating them, if it computes that
           this is safe, and replace them with descriptors.  Descriptors are
           made up of data only, but the generated code must be prepared to deal
           with them.  As of this writing, -fno-trampolines is enabled by
           default only for Ada.

           Moreover, code compiled with -ftrampolines and code compiled with
           -fno-trampolines are not binary compatible if nested functions are
           present.  This option must therefore be used on a program-wide basis
           and be manipulated with extreme care.

       -fvisibility=[default|internal|hidden|protected]
           Set the default ELF image symbol visibility to the specified
           option---all symbols are marked with this unless overridden within
           the code.  Using this feature can very substantially improve linking
           and load times of shared object libraries, produce more optimized
           code, provide near-perfect API export and prevent symbol clashes.  It
           is strongly recommended that you use this in any shared objects you
           distribute.

           Despite the nomenclature, default always means public; i.e.,
           available to be linked against from outside the shared object.
           protected and internal are pretty useless in real-world usage so the
           only other commonly used option is hidden.  The default if
           -fvisibility isn't specified is default, i.e., make every symbol
           public.

           A good explanation of the benefits offered by ensuring ELF symbols
           have the correct visibility is given by "How To Write Shared
           Libraries" by Ulrich Drepper (which can be found at
           <https://www.akkadia.org/drepper/>)---however a superior solution
           made possible by this option to marking things hidden when the
           default is public is to make the default hidden and mark things
           public.  This is the norm with DLLs on Windows and with
           -fvisibility=hidden and "__attribute__ ((visibility("default")))"
           instead of "__declspec(dllexport)" you get almost identical semantics
           with identical syntax.  This is a great boon to those working with
           cross-platform projects.

           For those adding visibility support to existing code, you may find
           "#pragma GCC visibility" of use.  This works by you enclosing the
           declarations you wish to set visibility for with (for example)
           "#pragma GCC visibility push(hidden)" and "#pragma GCC visibility
           pop".  Bear in mind that symbol visibility should be viewed as part
           of the API interface contract and thus all new code should always
           specify visibility when it is not the default; i.e., declarations
           only for use within the local DSO should always be marked explicitly
           as hidden as so to avoid PLT indirection overheads---making this
           abundantly clear also aids readability and self-documentation of the
           code.  Note that due to ISO C++ specification requirements, "operator
           new" and "operator delete" must always be of default visibility.

           Be aware that headers from outside your project, in particular system
           headers and headers from any other library you use, may not be
           expecting to be compiled with visibility other than the default.  You
           may need to explicitly say "#pragma GCC visibility push(default)"
           before including any such headers.

           "extern" declarations are not affected by -fvisibility, so a lot of
           code can be recompiled with -fvisibility=hidden with no
           modifications.  However, this means that calls to "extern" functions
           with no explicit visibility use the PLT, so it is more effective to
           use "__attribute ((visibility))" and/or "#pragma GCC visibility" to
           tell the compiler which "extern" declarations should be treated as
           hidden.

           Note that -fvisibility does affect C++ vague linkage entities. This
           means that, for instance, an exception class that is be thrown
           between DSOs must be explicitly marked with default visibility so
           that the type_info nodes are unified between the DSOs.

           An overview of these techniques, their benefits and how to use them
           is at <http://gcc.gnu.org/wiki/Visibility>.

       -fstrict-volatile-bitfields
           This option should be used if accesses to volatile bit-fields (or
           other structure fields, although the compiler usually honors those
           types anyway) should use a single access of the width of the field's
           type, aligned to a natural alignment if possible.  For example,
           targets with memory-mapped peripheral registers might require all
           such accesses to be 16 bits wide; with this flag you can declare all
           peripheral bit-fields as "unsigned short" (assuming short is 16 bits
           on these targets) to force GCC to use 16-bit accesses instead of,
           perhaps, a more efficient 32-bit access.

           If this option is disabled, the compiler uses the most efficient
           instruction.  In the previous example, that might be a 32-bit load
           instruction, even though that accesses bytes that do not contain any
           portion of the bit-field, or memory-mapped registers unrelated to the
           one being updated.

           In some cases, such as when the "packed" attribute is applied to a
           structure field, it may not be possible to access the field with a
           single read or write that is correctly aligned for the target
           machine.  In this case GCC falls back to generating multiple accesses
           rather than code that will fault or truncate the result at run time.

           Note:  Due to restrictions of the C/C++11 memory model, write
           accesses are not allowed to touch non bit-field members.  It is
           therefore recommended to define all bits of the field's type as bit-
           field members.

           The default value of this option is determined by the application
           binary interface for the target processor.

       -fsync-libcalls
           This option controls whether any out-of-line instance of the "__sync"
           family of functions may be used to implement the C++11 "__atomic"
           family of functions.

           The default value of this option is enabled, thus the only useful
           form of the option is -fno-sync-libcalls.  This option is used in the
           implementation of the libatomic runtime library.

   GCC Developer Options
       This section describes command-line options that are primarily of
       interest to GCC developers, including options to support compiler testing
       and investigation of compiler bugs and compile-time performance problems.
       This includes options that produce debug dumps at various points in the
       compilation; that print statistics such as memory use and execution time;
       and that print information about GCC's configuration, such as where it
       searches for libraries.  You should rarely need to use any of these
       options for ordinary compilation and linking tasks.

       Many developer options that cause GCC to dump output to a file take an
       optional =filename suffix. You can specify stdout or - to dump to
       standard output, and stderr for standard error.

       If =filename is omitted, a default dump file name is constructed by
       concatenating the base dump file name, a pass number, phase letter, and
       pass name.  The base dump file name is the name of output file produced
       by the compiler if explicitly specified and not an executable; otherwise
       it is the source file name.  The pass number is determined by the order
       passes are registered with the compiler's pass manager.  This is
       generally the same as the order of execution, but passes registered by
       plugins, target-specific passes, or passes that are otherwise registered
       late are numbered higher than the pass named final, even if they are
       executed earlier.  The phase letter is one of i (inter-procedural
       analysis), l (language-specific), r (RTL), or t (tree).  The files are
       created in the directory of the output file.

       -fcallgraph-info
       -fcallgraph-info=MARKERS
           Makes the compiler output callgraph information for the program, on a
           per-object-file basis.  The information is generated in the common
           VCG format.  It can be decorated with additional, per-node and/or
           per-edge information, if a list of comma-separated markers is
           additionally specified.  When the "su" marker is specified, the
           callgraph is decorated with stack usage information; it is equivalent
           to -fstack-usage.  When the "da" marker is specified, the callgraph
           is decorated with information about dynamically allocated objects.

           When compiling with -flto, no callgraph information is output along
           with the object file.  At LTO link time, -fcallgraph-info may
           generate multiple callgraph information files next to intermediate
           LTO output files.

       -dletters
       -fdump-rtl-pass
       -fdump-rtl-pass=filename
           Says to make debugging dumps during compilation at times specified by
           letters.  This is used for debugging the RTL-based passes of the
           compiler.

           Some -dletters switches have different meaning when -E is used for
           preprocessing.

           Debug dumps can be enabled with a -fdump-rtl switch or some -d option
           letters.  Here are the possible letters for use in pass and letters,
           and their meanings:

           -fdump-rtl-alignments
               Dump after branch alignments have been computed.

           -fdump-rtl-asmcons
               Dump after fixing rtl statements that have unsatisfied in/out
               constraints.

           -fdump-rtl-auto_inc_dec
               Dump after auto-inc-dec discovery.  This pass is only run on
               architectures that have auto inc or auto dec instructions.

           -fdump-rtl-barriers
               Dump after cleaning up the barrier instructions.

           -fdump-rtl-bbpart
               Dump after partitioning hot and cold basic blocks.

           -fdump-rtl-bbro
               Dump after block reordering.

           -fdump-rtl-btl1
           -fdump-rtl-btl2
               -fdump-rtl-btl1 and -fdump-rtl-btl2 enable dumping after the two
               branch target load optimization passes.

           -fdump-rtl-bypass
               Dump after jump bypassing and control flow optimizations.

           -fdump-rtl-combine
               Dump after the RTL instruction combination pass.

           -fdump-rtl-compgotos
               Dump after duplicating the computed gotos.

           -fdump-rtl-ce1
           -fdump-rtl-ce2
           -fdump-rtl-ce3
               -fdump-rtl-ce1, -fdump-rtl-ce2, and -fdump-rtl-ce3 enable dumping
               after the three if conversion passes.

           -fdump-rtl-cprop_hardreg
               Dump after hard register copy propagation.

           -fdump-rtl-csa
               Dump after combining stack adjustments.

           -fdump-rtl-cse1
           -fdump-rtl-cse2
               -fdump-rtl-cse1 and -fdump-rtl-cse2 enable dumping after the two
               common subexpression elimination passes.

           -fdump-rtl-dce
               Dump after the standalone dead code elimination passes.

           -fdump-rtl-dbr
               Dump after delayed branch scheduling.

           -fdump-rtl-dce1
           -fdump-rtl-dce2
               -fdump-rtl-dce1 and -fdump-rtl-dce2 enable dumping after the two
               dead store elimination passes.

           -fdump-rtl-eh
               Dump after finalization of EH handling code.

           -fdump-rtl-eh_ranges
               Dump after conversion of EH handling range regions.

           -fdump-rtl-expand
               Dump after RTL generation.

           -fdump-rtl-fwprop1
           -fdump-rtl-fwprop2
               -fdump-rtl-fwprop1 and -fdump-rtl-fwprop2 enable dumping after
               the two forward propagation passes.

           -fdump-rtl-gcse1
           -fdump-rtl-gcse2
               -fdump-rtl-gcse1 and -fdump-rtl-gcse2 enable dumping after global
               common subexpression elimination.

           -fdump-rtl-init-regs
               Dump after the initialization of the registers.

           -fdump-rtl-initvals
               Dump after the computation of the initial value sets.

           -fdump-rtl-into_cfglayout
               Dump after converting to cfglayout mode.

           -fdump-rtl-ira
               Dump after iterated register allocation.

           -fdump-rtl-jump
               Dump after the second jump optimization.

           -fdump-rtl-loop2
               -fdump-rtl-loop2 enables dumping after the rtl loop optimization
               passes.

           -fdump-rtl-mach
               Dump after performing the machine dependent reorganization pass,
               if that pass exists.

           -fdump-rtl-mode_sw
               Dump after removing redundant mode switches.

           -fdump-rtl-rnreg
               Dump after register renumbering.

           -fdump-rtl-outof_cfglayout
               Dump after converting from cfglayout mode.

           -fdump-rtl-peephole2
               Dump after the peephole pass.

           -fdump-rtl-postreload
               Dump after post-reload optimizations.

           -fdump-rtl-pro_and_epilogue
               Dump after generating the function prologues and epilogues.

           -fdump-rtl-sched1
           -fdump-rtl-sched2
               -fdump-rtl-sched1 and -fdump-rtl-sched2 enable dumping after the
               basic block scheduling passes.

           -fdump-rtl-ree
               Dump after sign/zero extension elimination.

           -fdump-rtl-seqabstr
               Dump after common sequence discovery.

           -fdump-rtl-shorten
               Dump after shortening branches.

           -fdump-rtl-sibling
               Dump after sibling call optimizations.

           -fdump-rtl-split1
           -fdump-rtl-split2
           -fdump-rtl-split3
           -fdump-rtl-split4
           -fdump-rtl-split5
               These options enable dumping after five rounds of instruction
               splitting.

           -fdump-rtl-sms
               Dump after modulo scheduling.  This pass is only run on some
               architectures.

           -fdump-rtl-stack
               Dump after conversion from GCC's "flat register file" registers
               to the x87's stack-like registers.  This pass is only run on x86
               variants.

           -fdump-rtl-subreg1
           -fdump-rtl-subreg2
               -fdump-rtl-subreg1 and -fdump-rtl-subreg2 enable dumping after
               the two subreg expansion passes.

           -fdump-rtl-unshare
               Dump after all rtl has been unshared.

           -fdump-rtl-vartrack
               Dump after variable tracking.

           -fdump-rtl-vregs
               Dump after converting virtual registers to hard registers.

           -fdump-rtl-web
               Dump after live range splitting.

           -fdump-rtl-regclass
           -fdump-rtl-subregs_of_mode_init
           -fdump-rtl-subregs_of_mode_finish
           -fdump-rtl-dfinit
           -fdump-rtl-dfinish
               These dumps are defined but always produce empty files.

           -da
           -fdump-rtl-all
               Produce all the dumps listed above.

           -dA Annotate the assembler output with miscellaneous debugging
               information.

           -dD Dump all macro definitions, at the end of preprocessing, in
               addition to normal output.

           -dH Produce a core dump whenever an error occurs.

           -dp Annotate the assembler output with a comment indicating which
               pattern and alternative is used.  The length and cost of each
               instruction are also printed.

           -dP Dump the RTL in the assembler output as a comment before each
               instruction.  Also turns on -dp annotation.

           -dx Just generate RTL for a function instead of compiling it.
               Usually used with -fdump-rtl-expand.

       -fdump-debug
           Dump debugging information generated during the debug generation
           phase.

       -fdump-earlydebug
           Dump debugging information generated during the early debug
           generation phase.

       -fdump-noaddr
           When doing debugging dumps, suppress address output.  This makes it
           more feasible to use diff on debugging dumps for compiler invocations
           with different compiler binaries and/or different text / bss / data /
           heap / stack / dso start locations.

       -freport-bug
           Collect and dump debug information into a temporary file if an
           internal compiler error (ICE) occurs.

       -fdump-unnumbered
           When doing debugging dumps, suppress instruction numbers and address
           output.  This makes it more feasible to use diff on debugging dumps
           for compiler invocations with different options, in particular with
           and without -g.

       -fdump-unnumbered-links
           When doing debugging dumps (see -d option above), suppress
           instruction numbers for the links to the previous and next
           instructions in a sequence.

       -fdump-ipa-switch
       -fdump-ipa-switch-options
           Control the dumping at various stages of inter-procedural analysis
           language tree to a file.  The file name is generated by appending a
           switch specific suffix to the source file name, and the file is
           created in the same directory as the output file.  The following
           dumps are possible:

           all Enables all inter-procedural analysis dumps.

           cgraph
               Dumps information about call-graph optimization, unused function
               removal, and inlining decisions.

           inline
               Dump after function inlining.

           Additionally, the options -optimized, -missed, -note, and -all can be
           provided, with the same meaning as for -fopt-info, defaulting to
           -optimized.

           For example, -fdump-ipa-inline-optimized-missed will emit information
           on callsites that were inlined, along with callsites that were not
           inlined.

           By default, the dump will contain messages about successful
           optimizations (equivalent to -optimized) together with low-level
           details about the analysis.

       -fdump-lang
           Dump language-specific information.  The file name is made by
           appending .lang to the source file name.

       -fdump-lang-all
       -fdump-lang-switch
       -fdump-lang-switch-options
       -fdump-lang-switch-options=filename
           Control the dumping of language-specific information.  The options
           and filename portions behave as described in the -fdump-tree option.
           The following switch values are accepted:

           all Enable all language-specific dumps.

           class
               Dump class hierarchy information.  Virtual table information is
               emitted unless 'slim' is specified.  This option is applicable to
               C++ only.

           module
               Dump module information.  Options lineno (locations), graph
               (reachability), blocks (clusters), uid (serialization), alias
               (mergeable), asmname (Elrond), eh (mapper) & vops (macros) may
               provide additional information.  This option is applicable to C++
               only.

           raw Dump the raw internal tree data.  This option is applicable to
               C++ only.

       -fdump-passes
           Print on stderr the list of optimization passes that are turned on
           and off by the current command-line options.

       -fdump-statistics-option
           Enable and control dumping of pass statistics in a separate file.
           The file name is generated by appending a suffix ending in
           .statistics to the source file name, and the file is created in the
           same directory as the output file.  If the -option form is used,
           -stats causes counters to be summed over the whole compilation unit
           while -details dumps every event as the passes generate them.  The
           default with no option is to sum counters for each function compiled.

       -fdump-tree-all
       -fdump-tree-switch
       -fdump-tree-switch-options
       -fdump-tree-switch-options=filename
           Control the dumping at various stages of processing the intermediate
           language tree to a file.  If the -options form is used, options is a
           list of - separated options which control the details of the dump.
           Not all options are applicable to all dumps; those that are not
           meaningful are ignored.  The following options are available

           address
               Print the address of each node.  Usually this is not meaningful
               as it changes according to the environment and source file.  Its
               primary use is for tying up a dump file with a debug environment.

           asmname
               If "DECL_ASSEMBLER_NAME" has been set for a given decl, use that
               in the dump instead of "DECL_NAME".  Its primary use is ease of
               use working backward from mangled names in the assembly file.

           slim
               When dumping front-end intermediate representations, inhibit
               dumping of members of a scope or body of a function merely
               because that scope has been reached.  Only dump such items when
               they are directly reachable by some other path.

               When dumping pretty-printed trees, this option inhibits dumping
               the bodies of control structures.

               When dumping RTL, print the RTL in slim (condensed) form instead
               of the default LISP-like representation.

           raw Print a raw representation of the tree.  By default, trees are
               pretty-printed into a C-like representation.

           details
               Enable more detailed dumps (not honored by every dump option).
               Also include information from the optimization passes.

           stats
               Enable dumping various statistics about the pass (not honored by
               every dump option).

           blocks
               Enable showing basic block boundaries (disabled in raw dumps).

           graph
               For each of the other indicated dump files (-fdump-rtl-pass),
               dump a representation of the control flow graph suitable for
               viewing with GraphViz to file.passid.pass.dot.  Each function in
               the file is pretty-printed as a subgraph, so that GraphViz can
               render them all in a single plot.

               This option currently only works for RTL dumps, and the RTL is
               always dumped in slim form.

           vops
               Enable showing virtual operands for every statement.

           lineno
               Enable showing line numbers for statements.

           uid Enable showing the unique ID ("DECL_UID") for each variable.

           verbose
               Enable showing the tree dump for each statement.

           eh  Enable showing the EH region number holding each statement.

           scev
               Enable showing scalar evolution analysis details.

           optimized
               Enable showing optimization information (only available in
               certain passes).

           missed
               Enable showing missed optimization information (only available in
               certain passes).

           note
               Enable other detailed optimization information (only available in
               certain passes).

           all Turn on all options, except raw, slim, verbose and lineno.

           optall
               Turn on all optimization options, i.e., optimized, missed, and
               note.

           To determine what tree dumps are available or find the dump for a
           pass of interest follow the steps below.

           1.  Invoke GCC with -fdump-passes and in the stderr output look for a
               code that corresponds to the pass you are interested in.  For
               example, the codes "tree-evrp", "tree-vrp1", and "tree-vrp2"
               correspond to the three Value Range Propagation passes.  The
               number at the end distinguishes distinct invocations of the same
               pass.

           2.  To enable the creation of the dump file, append the pass code to
               the -fdump- option prefix and invoke GCC with it.  For example,
               to enable the dump from the Early Value Range Propagation pass,
               invoke GCC with the -fdump-tree-evrp option.  Optionally, you may
               specify the name of the dump file.  If you don't specify one, GCC
               creates as described below.

           3.  Find the pass dump in a file whose name is composed of three
               components separated by a period: the name of the source file GCC
               was invoked to compile, a numeric suffix indicating the pass
               number followed by the letter t for tree passes (and the letter r
               for RTL passes), and finally the pass code.  For example, the
               Early VRP pass dump might be in a file named myfile.c.038t.evrp
               in the current working directory.  Note that the numeric codes
               are not stable and may change from one version of GCC to another.

       -fopt-info
       -fopt-info-options
       -fopt-info-options=filename
           Controls optimization dumps from various optimization passes. If the
           -options form is used, options is a list of - separated option
           keywords to select the dump details and optimizations.

           The options can be divided into three groups:

           1.  options describing what kinds of messages should be emitted,

           2.  options describing the verbosity of the dump, and

           3.  options describing which optimizations should be included.

           The options from each group can be freely mixed as they are non-
           overlapping. However, in case of any conflicts, the later options
           override the earlier options on the command line.

           The following options control which kinds of messages should be
           emitted:

           optimized
               Print information when an optimization is successfully applied.
               It is up to a pass to decide which information is relevant. For
               example, the vectorizer passes print the source location of loops
               which are successfully vectorized.

           missed
               Print information about missed optimizations. Individual passes
               control which information to include in the output.

           note
               Print verbose information about optimizations, such as certain
               transformations, more detailed messages about decisions etc.

           all Print detailed optimization information. This includes optimized,
               missed, and note.

           The following option controls the dump verbosity:

           internals
               By default, only "high-level" messages are emitted. This option
               enables additional, more detailed, messages, which are likely to
               only be of interest to GCC developers.

           One or more of the following option keywords can be used to describe
           a group of optimizations:

           ipa Enable dumps from all interprocedural optimizations.

           loop
               Enable dumps from all loop optimizations.

           inline
               Enable dumps from all inlining optimizations.

           omp Enable dumps from all OMP (Offloading and Multi Processing)
               optimizations.

           vec Enable dumps from all vectorization optimizations.

           optall
               Enable dumps from all optimizations. This is a superset of the
               optimization groups listed above.

           If options is omitted, it defaults to optimized-optall, which means
           to dump messages about successful optimizations from all the passes,
           omitting messages that are treated as "internals".

           If the filename is provided, then the dumps from all the applicable
           optimizations are concatenated into the filename.  Otherwise the dump
           is output onto stderr. Though multiple -fopt-info options are
           accepted, only one of them can include a filename. If other filenames
           are provided then all but the first such option are ignored.

           Note that the output filename is overwritten in case of multiple
           translation units. If a combined output from multiple translation
           units is desired, stderr should be used instead.

           In the following example, the optimization info is output to stderr:

                   gcc -O3 -fopt-info

           This example:

                   gcc -O3 -fopt-info-missed=missed.all

           outputs missed optimization report from all the passes into
           missed.all, and this one:

                   gcc -O2 -ftree-vectorize -fopt-info-vec-missed

           prints information about missed optimization opportunities from
           vectorization passes on stderr.  Note that -fopt-info-vec-missed is
           equivalent to -fopt-info-missed-vec.  The order of the optimization
           group names and message types listed after -fopt-info does not
           matter.

           As another example,

                   gcc -O3 -fopt-info-inline-optimized-missed=inline.txt

           outputs information about missed optimizations as well as optimized
           locations from all the inlining passes into inline.txt.

           Finally, consider:

                   gcc -fopt-info-vec-missed=vec.miss -fopt-info-loop-optimized=loop.opt

           Here the two output filenames vec.miss and loop.opt are in conflict
           since only one output file is allowed. In this case, only the first
           option takes effect and the subsequent options are ignored. Thus only
           vec.miss is produced which contains dumps from the vectorizer about
           missed opportunities.

       -fsave-optimization-record
           Write a SRCFILE.opt-record.json.gz file detailing what optimizations
           were performed, for those optimizations that support -fopt-info.

           This option is experimental and the format of the data within the
           compressed JSON file is subject to change.

           It is roughly equivalent to a machine-readable version of
           -fopt-info-all, as a collection of messages with source file, line
           number and column number, with the following additional data for each
           message:

           *   the execution count of the code being optimized, along with
               metadata about whether this was from actual profile data, or just
               an estimate, allowing consumers to prioritize messages by code
               hotness,

           *   the function name of the code being optimized, where applicable,

           *   the "inlining chain" for the code being optimized, so that when a
               function is inlined into several different places (which might
               themselves be inlined), the reader can distinguish between the
               copies,

           *   objects identifying those parts of the message that refer to
               expressions, statements or symbol-table nodes, which of these
               categories they are, and, when available, their source code
               location,

           *   the GCC pass that emitted the message, and

           *   the location in GCC's own code from which the message was emitted

           Additionally, some messages are logically nested within other
           messages, reflecting implementation details of the optimization
           passes.

       -fsched-verbose=n
           On targets that use instruction scheduling, this option controls the
           amount of debugging output the scheduler prints to the dump files.

           For n greater than zero, -fsched-verbose outputs the same information
           as -fdump-rtl-sched1 and -fdump-rtl-sched2.  For n greater than one,
           it also output basic block probabilities, detailed ready list
           information and unit/insn info.  For n greater than two, it includes
           RTL at abort point, control-flow and regions info.  And for n over
           four, -fsched-verbose also includes dependence info.

       -fenable-kind-pass
       -fdisable-kind-pass=range-list
           This is a set of options that are used to explicitly disable/enable
           optimization passes.  These options are intended for use for
           debugging GCC.  Compiler users should use regular options for
           enabling/disabling passes instead.

           -fdisable-ipa-pass
               Disable IPA pass pass. pass is the pass name.  If the same pass
               is statically invoked in the compiler multiple times, the pass
               name should be appended with a sequential number starting from 1.

           -fdisable-rtl-pass
           -fdisable-rtl-pass=range-list
               Disable RTL pass pass.  pass is the pass name.  If the same pass
               is statically invoked in the compiler multiple times, the pass
               name should be appended with a sequential number starting from 1.
               range-list is a comma-separated list of function ranges or
               assembler names.  Each range is a number pair separated by a
               colon.  The range is inclusive in both ends.  If the range is
               trivial, the number pair can be simplified as a single number.
               If the function's call graph node's uid falls within one of the
               specified ranges, the pass is disabled for that function.  The
               uid is shown in the function header of a dump file, and the pass
               names can be dumped by using option -fdump-passes.

           -fdisable-tree-pass
           -fdisable-tree-pass=range-list
               Disable tree pass pass.  See -fdisable-rtl for the description of
               option arguments.

           -fenable-ipa-pass
               Enable IPA pass pass.  pass is the pass name.  If the same pass
               is statically invoked in the compiler multiple times, the pass
               name should be appended with a sequential number starting from 1.

           -fenable-rtl-pass
           -fenable-rtl-pass=range-list
               Enable RTL pass pass.  See -fdisable-rtl for option argument
               description and examples.

           -fenable-tree-pass
           -fenable-tree-pass=range-list
               Enable tree pass pass.  See -fdisable-rtl for the description of
               option arguments.

           Here are some examples showing uses of these options.

                   # disable ccp1 for all functions
                      -fdisable-tree-ccp1
                   # disable complete unroll for function whose cgraph node uid is 1
                      -fenable-tree-cunroll=1
                   # disable gcse2 for functions at the following ranges [1,1],
                   # [300,400], and [400,1000]
                   # disable gcse2 for functions foo and foo2
                      -fdisable-rtl-gcse2=foo,foo2
                   # disable early inlining
                      -fdisable-tree-einline
                   # disable ipa inlining
                      -fdisable-ipa-inline
                   # enable tree full unroll
                      -fenable-tree-unroll

       -fchecking
       -fchecking=n
           Enable internal consistency checking.  The default depends on the
           compiler configuration.  -fchecking=2 enables further internal
           consistency checking that might affect code generation.

       -frandom-seed=string
           This option provides a seed that GCC uses in place of random numbers
           in generating certain symbol names that have to be different in every
           compiled file.  It is also used to place unique stamps in coverage
           data files and the object files that produce them.  You can use the
           -frandom-seed option to produce reproducibly identical object files.

           The string can either be a number (decimal, octal or hex) or an
           arbitrary string (in which case it's converted to a number by
           computing CRC32).

           The string should be different for every file you compile.

       -save-temps
           Store the usual "temporary" intermediate files permanently; name them
           as auxiliary output files, as specified described under -dumpbase and
           -dumpdir.

           When used in combination with the -x command-line option, -save-temps
           is sensible enough to avoid overwriting an input source file with the
           same extension as an intermediate file.  The corresponding
           intermediate file may be obtained by renaming the source file before
           using -save-temps.

       -save-temps=cwd
           Equivalent to -save-temps -dumpdir ./.

       -save-temps=obj
           Equivalent to -save-temps -dumpdir outdir/, where outdir/ is the
           directory of the output file specified after the -o option, including
           any directory separators.  If the -o option is not used, the
           -save-temps=obj switch behaves like -save-temps=cwd.

       -time[=file]
           Report the CPU time taken by each subprocess in the compilation
           sequence.  For C source files, this is the compiler proper and
           assembler (plus the linker if linking is done).

           Without the specification of an output file, the output looks like
           this:

                   # cc1 0.12 0.01
                   # as 0.00 0.01

           The first number on each line is the "user time", that is time spent
           executing the program itself.  The second number is "system time",
           time spent executing operating system routines on behalf of the
           program.  Both numbers are in seconds.

           With the specification of an output file, the output is appended to
           the named file, and it looks like this:

                   0.12 0.01 cc1 <options>
                   0.00 0.01 as <options>

           The "user time" and the "system time" are moved before the program
           name, and the options passed to the program are displayed, so that
           one can later tell what file was being compiled, and with which
           options.

       -fdump-final-insns[=file]
           Dump the final internal representation (RTL) to file.  If the
           optional argument is omitted (or if file is "."), the name of the
           dump file is determined by appending ".gkd" to the dump base name,
           see -dumpbase.

       -fcompare-debug[=opts]
           If no error occurs during compilation, run the compiler a second
           time, adding opts and -fcompare-debug-second to the arguments passed
           to the second compilation.  Dump the final internal representation in
           both compilations, and print an error if they differ.

           If the equal sign is omitted, the default -gtoggle is used.

           The environment variable GCC_COMPARE_DEBUG, if defined, non-empty and
           nonzero, implicitly enables -fcompare-debug.  If GCC_COMPARE_DEBUG is
           defined to a string starting with a dash, then it is used for opts,
           otherwise the default -gtoggle is used.

           -fcompare-debug=, with the equal sign but without opts, is equivalent
           to -fno-compare-debug, which disables the dumping of the final
           representation and the second compilation, preventing even
           GCC_COMPARE_DEBUG from taking effect.

           To verify full coverage during -fcompare-debug testing, set
           GCC_COMPARE_DEBUG to say -fcompare-debug-not-overridden, which GCC
           rejects as an invalid option in any actual compilation (rather than
           preprocessing, assembly or linking).  To get just a warning, setting
           GCC_COMPARE_DEBUG to -w%n-fcompare-debug not overridden will do.

       -fcompare-debug-second
           This option is implicitly passed to the compiler for the second
           compilation requested by -fcompare-debug, along with options to
           silence warnings, and omitting other options that would cause the
           compiler to produce output to files or to standard output as a side
           effect.  Dump files and preserved temporary files are renamed so as
           to contain the ".gk" additional extension during the second
           compilation, to avoid overwriting those generated by the first.

           When this option is passed to the compiler driver, it causes the
           first compilation to be skipped, which makes it useful for little
           other than debugging the compiler proper.

       -gtoggle
           Turn off generation of debug info, if leaving out this option
           generates it, or turn it on at level 2 otherwise.  The position of
           this argument in the command line does not matter; it takes effect
           after all other options are processed, and it does so only once, no
           matter how many times it is given.  This is mainly intended to be
           used with -fcompare-debug.

       -fvar-tracking-assignments-toggle
           Toggle -fvar-tracking-assignments, in the same way that -gtoggle
           toggles -g.

       -Q  Makes the compiler print out each function name as it is compiled,
           and print some statistics about each pass when it finishes.

       -ftime-report
           Makes the compiler print some statistics about the time consumed by
           each pass when it finishes.

       -ftime-report-details
           Record the time consumed by infrastructure parts separately for each
           pass.

       -fira-verbose=n
           Control the verbosity of the dump file for the integrated register
           allocator.  The default value is 5.  If the value n is greater or
           equal to 10, the dump output is sent to stderr using the same format
           as n minus 10.

       -flto-report
           Prints a report with internal details on the workings of the link-
           time optimizer.  The contents of this report vary from version to
           version.  It is meant to be useful to GCC developers when processing
           object files in LTO mode (via -flto).

           Disabled by default.

       -flto-report-wpa
           Like -flto-report, but only print for the WPA phase of link-time
           optimization.

       -fmem-report
           Makes the compiler print some statistics about permanent memory
           allocation when it finishes.

       -fmem-report-wpa
           Makes the compiler print some statistics about permanent memory
           allocation for the WPA phase only.

       -fpre-ipa-mem-report
       -fpost-ipa-mem-report
           Makes the compiler print some statistics about permanent memory
           allocation before or after interprocedural optimization.

       -fprofile-report
           Makes the compiler print some statistics about consistency of the
           (estimated) profile and effect of individual passes.

       -fstack-usage
           Makes the compiler output stack usage information for the program, on
           a per-function basis.  The filename for the dump is made by appending
           .su to the auxname.  auxname is generated from the name of the output
           file, if explicitly specified and it is not an executable, otherwise
           it is the basename of the source file.  An entry is made up of three
           fields:

           *   The name of the function.

           *   A number of bytes.

           *   One or more qualifiers: "static", "dynamic", "bounded".

           The qualifier "static" means that the function manipulates the stack
           statically: a fixed number of bytes are allocated for the frame on
           function entry and released on function exit; no stack adjustments
           are otherwise made in the function.  The second field is this fixed
           number of bytes.

           The qualifier "dynamic" means that the function manipulates the stack
           dynamically: in addition to the static allocation described above,
           stack adjustments are made in the body of the function, for example
           to push/pop arguments around function calls.  If the qualifier
           "bounded" is also present, the amount of these adjustments is bounded
           at compile time and the second field is an upper bound of the total
           amount of stack used by the function.  If it is not present, the
           amount of these adjustments is not bounded at compile time and the
           second field only represents the bounded part.

       -fstats
           Emit statistics about front-end processing at the end of the
           compilation.  This option is supported only by the C++ front end, and
           the information is generally only useful to the G++ development team.

       -fdbg-cnt-list
           Print the name and the counter upper bound for all debug counters.

       -fdbg-cnt=counter-value-list
           Set the internal debug counter lower and upper bound.  counter-value-
           list is a comma-separated list of name:lower_bound1-upper_bound1
           [:lower_bound2-upper_bound2...] tuples which sets the name of the
           counter and list of closed intervals.  The lower_bound is optional
           and is zero initialized if not set.  For example, with
           -fdbg-cnt=dce:2-4:10-11,tail_call:10, "dbg_cnt(dce)" returns true
           only for second, third, fourth, tenth and eleventh invocation.  For
           "dbg_cnt(tail_call)" true is returned for first 10 invocations.

       -print-file-name=library
           Print the full absolute name of the library file library that would
           be used when linking---and don't do anything else.  With this option,
           GCC does not compile or link anything; it just prints the file name.

       -print-multi-directory
           Print the directory name corresponding to the multilib selected by
           any other switches present in the command line.  This directory is
           supposed to exist in GCC_EXEC_PREFIX.

       -print-multi-lib
           Print the mapping from multilib directory names to compiler switches
           that enable them.  The directory name is separated from the switches
           by ;, and each switch starts with an @ instead of the -, without
           spaces between multiple switches.  This is supposed to ease shell
           processing.

       -print-multi-os-directory
           Print the path to OS libraries for the selected multilib, relative to
           some lib subdirectory.  If OS libraries are present in the lib
           subdirectory and no multilibs are used, this is usually just ., if OS
           libraries are present in libsuffix sibling directories this prints
           e.g. ../lib64, ../lib or ../lib32, or if OS libraries are present in
           lib/subdir subdirectories it prints e.g. amd64, sparcv9 or ev6.

       -print-multiarch
           Print the path to OS libraries for the selected multiarch, relative
           to some lib subdirectory.

       -print-prog-name=program
           Like -print-file-name, but searches for a program such as cpp.

       -print-libgcc-file-name
           Same as -print-file-name=libgcc.a.

           This is useful when you use -nostdlib or -nodefaultlibs but you do
           want to link with libgcc.a.  You can do:

                   gcc -nostdlib <files>... `gcc -print-libgcc-file-name`

       -print-search-dirs
           Print the name of the configured installation directory and a list of
           program and library directories gcc searches---and don't do anything
           else.

           This is useful when gcc prints the error message installation
           problem, cannot exec cpp0: No such file or directory.  To resolve
           this you either need to put cpp0 and the other compiler components
           where gcc expects to find them, or you can set the environment
           variable GCC_EXEC_PREFIX to the directory where you installed them.
           Don't forget the trailing /.

       -print-sysroot
           Print the target sysroot directory that is used during compilation.
           This is the target sysroot specified either at configure time or
           using the --sysroot option, possibly with an extra suffix that
           depends on compilation options.  If no target sysroot is specified,
           the option prints nothing.

       -print-sysroot-headers-suffix
           Print the suffix added to the target sysroot when searching for
           headers, or give an error if the compiler is not configured with such
           a suffix---and don't do anything else.

       -dumpmachine
           Print the compiler's target machine (for example,
           i686-pc-linux-gnu)---and don't do anything else.

       -dumpversion
           Print the compiler version (for example, 3.0, 6.3.0 or 7)---and don't
           do anything else.  This is the compiler version used in filesystem
           paths and specs. Depending on how the compiler has been configured it
           can be just a single number (major version), two numbers separated by
           a dot (major and minor version) or three numbers separated by dots
           (major, minor and patchlevel version).

       -dumpfullversion
           Print the full compiler version---and don't do anything else. The
           output is always three numbers separated by dots, major, minor and
           patchlevel version.

       -dumpspecs
           Print the compiler's built-in specs---and don't do anything else.
           (This is used when GCC itself is being built.)

   Machine-Dependent Options
       Each target machine supported by GCC can have its own options---for
       example, to allow you to compile for a particular processor variant or
       ABI, or to control optimizations specific to that machine.  By
       convention, the names of machine-specific options start with -m.

       Some configurations of the compiler also support additional target-
       specific options, usually for compatibility with other compilers on the
       same platform.

       AArch64 Options

       These options are defined for AArch64 implementations:

       -mabi=name
           Generate code for the specified data model.  Permissible values are
           ilp32 for SysV-like data model where int, long int and pointers are
           32 bits, and lp64 for SysV-like data model where int is 32 bits, but
           long int and pointers are 64 bits.

           The default depends on the specific target configuration.  Note that
           the LP64 and ILP32 ABIs are not link-compatible; you must compile
           your entire program with the same ABI, and link with a compatible set
           of libraries.

       -mbig-endian
           Generate big-endian code.  This is the default when GCC is configured
           for an aarch64_be-*-* target.

       -mgeneral-regs-only
           Generate code which uses only the general-purpose registers.  This
           will prevent the compiler from using floating-point and Advanced SIMD
           registers but will not impose any restrictions on the assembler.

       -mlittle-endian
           Generate little-endian code.  This is the default when GCC is
           configured for an aarch64-*-* but not an aarch64_be-*-* target.

       -mcmodel=tiny
           Generate code for the tiny code model.  The program and its
           statically defined symbols must be within 1MB of each other.
           Programs can be statically or dynamically linked.

       -mcmodel=small
           Generate code for the small code model.  The program and its
           statically defined symbols must be within 4GB of each other.
           Programs can be statically or dynamically linked.  This is the
           default code model.

       -mcmodel=large
           Generate code for the large code model.  This makes no assumptions
           about addresses and sizes of sections.  Programs can be statically
           linked only.  The -mcmodel=large option is incompatible with
           -mabi=ilp32, -fpic and -fPIC.

       -mstrict-align
       -mno-strict-align
           Avoid or allow generating memory accesses that may not be aligned on
           a natural object boundary as described in the architecture
           specification.

       -momit-leaf-frame-pointer
       -mno-omit-leaf-frame-pointer
           Omit or keep the frame pointer in leaf functions.  The former
           behavior is the default.

       -mstack-protector-guard=guard
       -mstack-protector-guard-reg=reg
       -mstack-protector-guard-offset=offset
           Generate stack protection code using canary at guard.  Supported
           locations are global for a global canary or sysreg for a canary in an
           appropriate system register.

           With the latter choice the options -mstack-protector-guard-reg=reg
           and -mstack-protector-guard-offset=offset furthermore specify which
           system register to use as base register for reading the canary, and
           from what offset from that base register. There is no default
           register or offset as this is entirely for use within the Linux
           kernel.

       -mtls-dialect=desc
           Use TLS descriptors as the thread-local storage mechanism for dynamic
           accesses of TLS variables.  This is the default.

       -mtls-dialect=traditional
           Use traditional TLS as the thread-local storage mechanism for dynamic
           accesses of TLS variables.

       -mtls-size=size
           Specify bit size of immediate TLS offsets.  Valid values are 12, 24,
           32, 48.  This option requires binutils 2.26 or newer.

       -mfix-cortex-a53-835769
       -mno-fix-cortex-a53-835769
           Enable or disable the workaround for the ARM Cortex-A53 erratum
           number 835769.  This involves inserting a NOP instruction between
           memory instructions and 64-bit integer multiply-accumulate
           instructions.

       -mfix-cortex-a53-843419
       -mno-fix-cortex-a53-843419
           Enable or disable the workaround for the ARM Cortex-A53 erratum
           number 843419.  This erratum workaround is made at link time and this
           will only pass the corresponding flag to the linker.

       -mlow-precision-recip-sqrt
       -mno-low-precision-recip-sqrt
           Enable or disable the reciprocal square root approximation.  This
           option only has an effect if -ffast-math or
           -funsafe-math-optimizations is used as well.  Enabling this reduces
           precision of reciprocal square root results to about 16 bits for
           single precision and to 32 bits for double precision.

       -mlow-precision-sqrt
       -mno-low-precision-sqrt
           Enable or disable the square root approximation.  This option only
           has an effect if -ffast-math or -funsafe-math-optimizations is used
           as well.  Enabling this reduces precision of square root results to
           about 16 bits for single precision and to 32 bits for double
           precision.  If enabled, it implies -mlow-precision-recip-sqrt.

       -mlow-precision-div
       -mno-low-precision-div
           Enable or disable the division approximation.  This option only has
           an effect if -ffast-math or -funsafe-math-optimizations is used as
           well.  Enabling this reduces precision of division results to about
           16 bits for single precision and to 32 bits for double precision.

       -mtrack-speculation
       -mno-track-speculation
           Enable or disable generation of additional code to track speculative
           execution through conditional branches.  The tracking state can then
           be used by the compiler when expanding calls to
           "__builtin_speculation_safe_copy" to permit a more efficient code
           sequence to be generated.

       -moutline-atomics
       -mno-outline-atomics
           Enable or disable calls to out-of-line helpers to implement atomic
           operations.  These helpers will, at runtime, determine if the LSE
           instructions from ARMv8.1-A can be used; if not, they will use the
           load/store-exclusive instructions that are present in the base
           ARMv8.0 ISA.

           This option is only applicable when compiling for the base ARMv8.0
           instruction set.  If using a later revision, e.g. -march=armv8.1-a or
           -march=armv8-a+lse, the ARMv8.1-Atomics instructions will be used
           directly.  The same applies when using -mcpu= when the selected cpu
           supports the lse feature.  This option is on by default.

       -march=name
           Specify the name of the target architecture and, optionally, one or
           more feature modifiers.  This option has the form
           -march=arch{+[no]feature}*.

           The table below summarizes the permissible values for arch and the
           features that they enable by default:

           arch value : Architecture : Includes by default
           armv8-a : Armv8-A : +fp, +simd
           armv8.1-a : Armv8.1-A : armv8-a, +crc, +lse, +rdma
           armv8.2-a : Armv8.2-A : armv8.1-a
           armv8.3-a : Armv8.3-A : armv8.2-a, +pauth
           armv8.4-a : Armv8.4-A : armv8.3-a, +flagm, +fp16fml, +dotprod
           armv8.5-a : Armv8.5-A : armv8.4-a, +sb, +ssbs, +predres
           armv8.6-a : Armv8.6-A : armv8.5-a, +bf16, +i8mm
           armv8-r : Armv8-R : armv8-r

           The value native is available on native AArch64 GNU/Linux and causes
           the compiler to pick the architecture of the host system.  This
           option has no effect if the compiler is unable to recognize the
           architecture of the host system,

           The permissible values for feature are listed in the sub-section on
           aarch64-feature-modifiers,,-march and -mcpu Feature Modifiers.  Where
           conflicting feature modifiers are specified, the right-most feature
           is used.

           GCC uses name to determine what kind of instructions it can emit when
           generating assembly code.  If -march is specified without either of
           -mtune or -mcpu also being specified, the code is tuned to perform
           well across a range of target processors implementing the target
           architecture.

       -mtune=name
           Specify the name of the target processor for which GCC should tune
           the performance of the code.  Permissible values for this option are:
           generic, cortex-a35, cortex-a53, cortex-a55, cortex-a57, cortex-a72,
           cortex-a73, cortex-a75, cortex-a76, cortex-a76ae, cortex-a77,
           cortex-a65, cortex-a65ae, cortex-a34, cortex-a78, cortex-a78ae,
           cortex-a78c, ares, exynos-m1, emag, falkor, neoverse-e1, neoverse-n1,
           neoverse-n2, neoverse-v1, qdf24xx, saphira, phecda, xgene1, vulcan,
           octeontx, octeontx81,  octeontx83, octeontx2, octeontx2t98,
           octeontx2t96 octeontx2t93, octeontx2f95, octeontx2f95n,
           octeontx2f95mm, a64fx, thunderx, thunderxt88, thunderxt88p1,
           thunderxt81, tsv110, thunderxt83, thunderx2t99, thunderx3t110, zeus,
           cortex-a57.cortex-a53, cortex-a72.cortex-a53, cortex-a73.cortex-a35,
           cortex-a73.cortex-a53, cortex-a75.cortex-a55, cortex-a76.cortex-a55,
           cortex-r82, cortex-x1, native.

           The values cortex-a57.cortex-a53, cortex-a72.cortex-a53,
           cortex-a73.cortex-a35, cortex-a73.cortex-a53, cortex-a75.cortex-a55,
           cortex-a76.cortex-a55 specify that GCC should tune for a big.LITTLE
           system.

           Additionally on native AArch64 GNU/Linux systems the value native
           tunes performance to the host system.  This option has no effect if
           the compiler is unable to recognize the processor of the host system.

           Where none of -mtune=, -mcpu= or -march= are specified, the code is
           tuned to perform well across a range of target processors.

           This option cannot be suffixed by feature modifiers.

       -mcpu=name
           Specify the name of the target processor, optionally suffixed by one
           or more feature modifiers.  This option has the form
           -mcpu=cpu{+[no]feature}*, where the permissible values for cpu are
           the same as those available for -mtune.  The permissible values for
           feature are documented in the sub-section on
           aarch64-feature-modifiers,,-march and -mcpu Feature Modifiers.  Where
           conflicting feature modifiers are specified, the right-most feature
           is used.

           GCC uses name to determine what kind of instructions it can emit when
           generating assembly code (as if by -march) and to determine the
           target processor for which to tune for performance (as if by -mtune).
           Where this option is used in conjunction with -march or -mtune, those
           options take precedence over the appropriate part of this option.

       -moverride=string
           Override tuning decisions made by the back-end in response to a
           -mtune= switch.  The syntax, semantics, and accepted values for
           string in this option are not guaranteed to be consistent across
           releases.

           This option is only intended to be useful when developing GCC.

       -mverbose-cost-dump
           Enable verbose cost model dumping in the debug dump files.  This
           option is provided for use in debugging the compiler.

       -mpc-relative-literal-loads
       -mno-pc-relative-literal-loads
           Enable or disable PC-relative literal loads.  With this option
           literal pools are accessed using a single instruction and emitted
           after each function.  This limits the maximum size of functions to
           1MB.  This is enabled by default for -mcmodel=tiny.

       -msign-return-address=scope
           Select the function scope on which return address signing will be
           applied.  Permissible values are none, which disables return address
           signing, non-leaf, which enables pointer signing for functions which
           are not leaf functions, and all, which enables pointer signing for
           all functions.  The default value is none. This option has been
           deprecated by -mbranch-protection.

       -mbranch-protection=none|standard|pac-ret[+leaf+b-key]|bti
           Select the branch protection features to use.  none is the default
           and turns off all types of branch protection.  standard turns on all
           types of branch protection features.  If a feature has additional
           tuning options, then standard sets it to its standard level.
           pac-ret[+leaf] turns on return address signing to its standard level:
           signing functions that save the return address to memory (non-leaf
           functions will practically always do this) using the a-key.  The
           optional argument leaf can be used to extend the signing to include
           leaf functions.  The optional argument b-key can be used to sign the
           functions with the B-key instead of the A-key.  bti turns on branch
           target identification mechanism.

       -mharden-sls=opts
           Enable compiler hardening against straight line speculation (SLS).
           opts is a comma-separated list of the following options:

           retbr
           blr

           In addition, -mharden-sls=all enables all SLS hardening while
           -mharden-sls=none disables all SLS hardening.

       -msve-vector-bits=bits
           Specify the number of bits in an SVE vector register.  This option
           only has an effect when SVE is enabled.

           GCC supports two forms of SVE code generation: "vector-length
           agnostic" output that works with any size of vector register and
           "vector-length specific" output that allows GCC to make assumptions
           about the vector length when it is useful for optimization reasons.
           The possible values of bits are: scalable, 128, 256, 512, 1024 and
           2048.  Specifying scalable selects vector-length agnostic output.  At
           present -msve-vector-bits=128 also generates vector-length agnostic
           output for big-endian targets.  All other values generate vector-
           length specific code.  The behavior of these values may change in
           future releases and no value except scalable should be relied on for
           producing code that is portable across different hardware SVE vector
           lengths.

           The default is -msve-vector-bits=scalable, which produces vector-
           length agnostic code.

       -march and -mcpu Feature Modifiers

       Feature modifiers used with -march and -mcpu can be any of the following
       and their inverses nofeature:

       crc Enable CRC extension.  This is on by default for -march=armv8.1-a.

       crypto
           Enable Crypto extension.  This also enables Advanced SIMD and
           floating-point instructions.

       fp  Enable floating-point instructions.  This is on by default for all
           possible values for options -march and -mcpu.

       simd
           Enable Advanced SIMD instructions.  This also enables floating-point
           instructions.  This is on by default for all possible values for
           options -march and -mcpu.

       sve Enable Scalable Vector Extension instructions.  This also enables
           Advanced SIMD and floating-point instructions.

       lse Enable Large System Extension instructions.  This is on by default
           for -march=armv8.1-a.

       rdma
           Enable Round Double Multiply Accumulate instructions.  This is on by
           default for -march=armv8.1-a.

       fp16
           Enable FP16 extension.  This also enables floating-point
           instructions.

       fp16fml
           Enable FP16 fmla extension.  This also enables FP16 extensions and
           floating-point instructions. This option is enabled by default for
           -march=armv8.4-a. Use of this option with architectures prior to
           Armv8.2-A is not supported.

       rcpc
           Enable the RcPc extension.  This does not change code generation from
           GCC, but is passed on to the assembler, enabling inline asm
           statements to use instructions from the RcPc extension.

       dotprod
           Enable the Dot Product extension.  This also enables Advanced SIMD
           instructions.

       aes Enable the Armv8-a aes and pmull crypto extension.  This also enables
           Advanced SIMD instructions.

       sha2
           Enable the Armv8-a sha2 crypto extension.  This also enables Advanced
           SIMD instructions.

       sha3
           Enable the sha512 and sha3 crypto extension.  This also enables
           Advanced SIMD instructions. Use of this option with architectures
           prior to Armv8.2-A is not supported.

       sm4 Enable the sm3 and sm4 crypto extension.  This also enables Advanced
           SIMD instructions.  Use of this option with architectures prior to
           Armv8.2-A is not supported.

       profile
           Enable the Statistical Profiling extension.  This option is only to
           enable the extension at the assembler level and does not affect code
           generation.

       rng Enable the Armv8.5-a Random Number instructions.  This option is only
           to enable the extension at the assembler level and does not affect
           code generation.

       memtag
           Enable the Armv8.5-a Memory Tagging Extensions.  Use of this option
           with architectures prior to Armv8.5-A is not supported.

       sb  Enable the Armv8-a Speculation Barrier instruction.  This option is
           only to enable the extension at the assembler level and does not
           affect code generation.  This option is enabled by default for
           -march=armv8.5-a.

       ssbs
           Enable the Armv8-a Speculative Store Bypass Safe instruction.  This
           option is only to enable the extension at the assembler level and
           does not affect code generation.  This option is enabled by default
           for -march=armv8.5-a.

       predres
           Enable the Armv8-a Execution and Data Prediction Restriction
           instructions.  This option is only to enable the extension at the
           assembler level and does not affect code generation.  This option is
           enabled by default for -march=armv8.5-a.

       sve2
           Enable the Armv8-a Scalable Vector Extension 2.  This also enables
           SVE instructions.

       sve2-bitperm
           Enable SVE2 bitperm instructions.  This also enables SVE2
           instructions.

       sve2-sm4
           Enable SVE2 sm4 instructions.  This also enables SVE2 instructions.

       sve2-aes
           Enable SVE2 aes instructions.  This also enables SVE2 instructions.

       sve2-sha3
           Enable SVE2 sha3 instructions.  This also enables SVE2 instructions.

       tme Enable the Transactional Memory Extension.

       i8mm
           Enable 8-bit Integer Matrix Multiply instructions.  This also enables
           Advanced SIMD and floating-point instructions.  This option is
           enabled by default for -march=armv8.6-a.  Use of this option with
           architectures prior to Armv8.2-A is not supported.

       f32mm
           Enable 32-bit Floating point Matrix Multiply instructions.  This also
           enables SVE instructions.  Use of this option with architectures
           prior to Armv8.2-A is not supported.

       f64mm
           Enable 64-bit Floating point Matrix Multiply instructions.  This also
           enables SVE instructions.  Use of this option with architectures
           prior to Armv8.2-A is not supported.

       bf16
           Enable brain half-precision floating-point instructions.  This also
           enables Advanced SIMD and floating-point instructions.  This option
           is enabled by default for -march=armv8.6-a.  Use of this option with
           architectures prior to Armv8.2-A is not supported.

       flagm
           Enable the Flag Manipulation instructions Extension.

       pauth
           Enable the Pointer Authentication Extension.

       Feature crypto implies aes, sha2, and simd, which implies fp.
       Conversely, nofp implies nosimd, which implies nocrypto, noaes and
       nosha2.

       Adapteva Epiphany Options

       These -m options are defined for Adapteva Epiphany:

       -mhalf-reg-file
           Don't allocate any register in the range "r32"..."r63".  That allows
           code to run on hardware variants that lack these registers.

       -mprefer-short-insn-regs
           Preferentially allocate registers that allow short instruction
           generation.  This can result in increased instruction count, so this
           may either reduce or increase overall code size.

       -mbranch-cost=num
           Set the cost of branches to roughly num "simple" instructions.  This
           cost is only a heuristic and is not guaranteed to produce consistent
           results across releases.

       -mcmove
           Enable the generation of conditional moves.

       -mnops=num
           Emit num NOPs before every other generated instruction.

       -mno-soft-cmpsf
           For single-precision floating-point comparisons, emit an "fsub"
           instruction and test the flags.  This is faster than a software
           comparison, but can get incorrect results in the presence of NaNs, or
           when two different small numbers are compared such that their
           difference is calculated as zero.  The default is -msoft-cmpsf, which
           uses slower, but IEEE-compliant, software comparisons.

       -mstack-offset=num
           Set the offset between the top of the stack and the stack pointer.
           E.g., a value of 8 means that the eight bytes in the range
           "sp+0...sp+7" can be used by leaf functions without stack allocation.
           Values other than 8 or 16 are untested and unlikely to work.  Note
           also that this option changes the ABI; compiling a program with a
           different stack offset than the libraries have been compiled with
           generally does not work.  This option can be useful if you want to
           evaluate if a different stack offset would give you better code, but
           to actually use a different stack offset to build working programs,
           it is recommended to configure the toolchain with the appropriate
           --with-stack-offset=num option.

       -mno-round-nearest
           Make the scheduler assume that the rounding mode has been set to
           truncating.  The default is -mround-nearest.

       -mlong-calls
           If not otherwise specified by an attribute, assume all calls might be
           beyond the offset range of the "b" / "bl" instructions, and therefore
           load the function address into a register before performing a
           (otherwise direct) call.  This is the default.

       -mshort-calls
           If not otherwise specified by an attribute, assume all direct calls
           are in the range of the "b" / "bl" instructions, so use these
           instructions for direct calls.  The default is -mlong-calls.

       -msmall16
           Assume addresses can be loaded as 16-bit unsigned values.  This does
           not apply to function addresses for which -mlong-calls semantics are
           in effect.

       -mfp-mode=mode
           Set the prevailing mode of the floating-point unit.  This determines
           the floating-point mode that is provided and expected at function
           call and return time.  Making this mode match the mode you
           predominantly need at function start can make your programs smaller
           and faster by avoiding unnecessary mode switches.

           mode can be set to one the following values:

           caller
               Any mode at function entry is valid, and retained or restored
               when the function returns, and when it calls other functions.
               This mode is useful for compiling libraries or other compilation
               units you might want to incorporate into different programs with
               different prevailing FPU modes, and the convenience of being able
               to use a single object file outweighs the size and speed overhead
               for any extra mode switching that might be needed, compared with
               what would be needed with a more specific choice of prevailing
               FPU mode.

           truncate
               This is the mode used for floating-point calculations with
               truncating (i.e. round towards zero) rounding mode.  That
               includes conversion from floating point to integer.

           round-nearest
               This is the mode used for floating-point calculations with round-
               to-nearest-or-even rounding mode.

           int This is the mode used to perform integer calculations in the FPU,
               e.g.  integer multiply, or integer multiply-and-accumulate.

           The default is -mfp-mode=caller

       -mno-split-lohi
       -mno-postinc
       -mno-postmodify
           Code generation tweaks that disable, respectively, splitting of
           32-bit loads, generation of post-increment addresses, and generation
           of post-modify addresses.  The defaults are msplit-lohi, -mpost-inc,
           and -mpost-modify.

       -mnovect-double
           Change the preferred SIMD mode to SImode.  The default is
           -mvect-double, which uses DImode as preferred SIMD mode.

       -max-vect-align=num
           The maximum alignment for SIMD vector mode types.  num may be 4 or 8.
           The default is 8.  Note that this is an ABI change, even though many
           library function interfaces are unaffected if they don't use SIMD
           vector modes in places that affect size and/or alignment of relevant
           types.

       -msplit-vecmove-early
           Split vector moves into single word moves before reload.  In theory
           this can give better register allocation, but so far the reverse
           seems to be generally the case.

       -m1reg-reg
           Specify a register to hold the constant -1, which makes loading small
           negative constants and certain bitmasks faster.  Allowable values for
           reg are r43 and r63, which specify use of that register as a fixed
           register, and none, which means that no register is used for this
           purpose.  The default is -m1reg-none.

       AMD GCN Options

       These options are defined specifically for the AMD GCN port.

       -march=gpu
       -mtune=gpu
           Set architecture type or tuning for gpu. Supported values for gpu are

           fiji
               Compile for GCN3 Fiji devices (gfx803).

           gfx900
               Compile for GCN5 Vega 10 devices (gfx900).

           gfx906
               Compile for GCN5 Vega 20 devices (gfx906).

       -mstack-size=bytes
           Specify how many bytes of stack space will be requested for each GPU
           thread (wave-front).  Beware that there may be many threads and
           limited memory available.  The size of the stack allocation may also
           have an impact on run-time performance.  The default is 32KB when
           using OpenACC or OpenMP, and 1MB otherwise.

       ARC Options

       The following options control the architecture variant for which code is
       being compiled:

       -mbarrel-shifter
           Generate instructions supported by barrel shifter.  This is the
           default unless -mcpu=ARC601 or -mcpu=ARCEM is in effect.

       -mjli-always
           Force to call a function using jli_s instruction.  This option is
           valid only for ARCv2 architecture.

       -mcpu=cpu
           Set architecture type, register usage, and instruction scheduling
           parameters for cpu.  There are also shortcut alias options available
           for backward compatibility and convenience.  Supported values for cpu
           are

           arc600
               Compile for ARC600.  Aliases: -mA6, -mARC600.

           arc601
               Compile for ARC601.  Alias: -mARC601.

           arc700
               Compile for ARC700.  Aliases: -mA7, -mARC700.  This is the
               default when configured with --with-cpu=arc700.

           arcem
               Compile for ARC EM.

           archs
               Compile for ARC HS.

           em  Compile for ARC EM CPU with no hardware extensions.

           em4 Compile for ARC EM4 CPU.

           em4_dmips
               Compile for ARC EM4 DMIPS CPU.

           em4_fpus
               Compile for ARC EM4 DMIPS CPU with the single-precision floating-
               point extension.

           em4_fpuda
               Compile for ARC EM4 DMIPS CPU with single-precision floating-
               point and double assist instructions.

           hs  Compile for ARC HS CPU with no hardware extensions except the
               atomic instructions.

           hs34
               Compile for ARC HS34 CPU.

           hs38
               Compile for ARC HS38 CPU.

           hs38_linux
               Compile for ARC HS38 CPU with all hardware extensions on.

           arc600_norm
               Compile for ARC 600 CPU with "norm" instructions enabled.

           arc600_mul32x16
               Compile for ARC 600 CPU with "norm" and 32x16-bit multiply
               instructions enabled.

           arc600_mul64
               Compile for ARC 600 CPU with "norm" and "mul64"-family
               instructions enabled.

           arc601_norm
               Compile for ARC 601 CPU with "norm" instructions enabled.

           arc601_mul32x16
               Compile for ARC 601 CPU with "norm" and 32x16-bit multiply
               instructions enabled.

           arc601_mul64
               Compile for ARC 601 CPU with "norm" and "mul64"-family
               instructions enabled.

           nps400
               Compile for ARC 700 on NPS400 chip.

           em_mini
               Compile for ARC EM minimalist configuration featuring reduced
               register set.

       -mdpfp
       -mdpfp-compact
           Generate double-precision FPX instructions, tuned for the compact
           implementation.

       -mdpfp-fast
           Generate double-precision FPX instructions, tuned for the fast
           implementation.

       -mno-dpfp-lrsr
           Disable "lr" and "sr" instructions from using FPX extension aux
           registers.

       -mea
           Generate extended arithmetic instructions.  Currently only "divaw",
           "adds", "subs", and "sat16" are supported.  Only valid for
           -mcpu=ARC700.

       -mno-mpy
           Do not generate "mpy"-family instructions for ARC700.  This option is
           deprecated.

       -mmul32x16
           Generate 32x16-bit multiply and multiply-accumulate instructions.

       -mmul64
           Generate "mul64" and "mulu64" instructions.  Only valid for
           -mcpu=ARC600.

       -mnorm
           Generate "norm" instructions.  This is the default if -mcpu=ARC700 is
           in effect.

       -mspfp
       -mspfp-compact
           Generate single-precision FPX instructions, tuned for the compact
           implementation.

       -mspfp-fast
           Generate single-precision FPX instructions, tuned for the fast
           implementation.

       -msimd
           Enable generation of ARC SIMD instructions via target-specific
           builtins.  Only valid for -mcpu=ARC700.

       -msoft-float
           This option ignored; it is provided for compatibility purposes only.
           Software floating-point code is emitted by default, and this default
           can overridden by FPX options; -mspfp, -mspfp-compact, or -mspfp-fast
           for single precision, and -mdpfp, -mdpfp-compact, or -mdpfp-fast for
           double precision.

       -mswap
           Generate "swap" instructions.

       -matomic
           This enables use of the locked load/store conditional extension to
           implement atomic memory built-in functions.  Not available for ARC
           6xx or ARC EM cores.

       -mdiv-rem
           Enable "div" and "rem" instructions for ARCv2 cores.

       -mcode-density
           Enable code density instructions for ARC EM.  This option is on by
           default for ARC HS.

       -mll64
           Enable double load/store operations for ARC HS cores.

       -mtp-regno=regno
           Specify thread pointer register number.

       -mmpy-option=multo
           Compile ARCv2 code with a multiplier design option.  You can specify
           the option using either a string or numeric value for multo.  wlh1 is
           the default value.  The recognized values are:

           0
           none
               No multiplier available.

           1
           w   16x16 multiplier, fully pipelined.  The following instructions
               are enabled: "mpyw" and "mpyuw".

           2
           wlh1
               32x32 multiplier, fully pipelined (1 stage).  The following
               instructions are additionally enabled: "mpy", "mpyu", "mpym",
               "mpymu", and "mpy_s".

           3
           wlh2
               32x32 multiplier, fully pipelined (2 stages).  The following
               instructions are additionally enabled: "mpy", "mpyu", "mpym",
               "mpymu", and "mpy_s".

           4
           wlh3
               Two 16x16 multipliers, blocking, sequential.  The following
               instructions are additionally enabled: "mpy", "mpyu", "mpym",
               "mpymu", and "mpy_s".

           5
           wlh4
               One 16x16 multiplier, blocking, sequential.  The following
               instructions are additionally enabled: "mpy", "mpyu", "mpym",
               "mpymu", and "mpy_s".

           6
           wlh5
               One 32x4 multiplier, blocking, sequential.  The following
               instructions are additionally enabled: "mpy", "mpyu", "mpym",
               "mpymu", and "mpy_s".

           7
           plus_dmpy
               ARC HS SIMD support.

           8
           plus_macd
               ARC HS SIMD support.

           9
           plus_qmacw
               ARC HS SIMD support.

           This option is only available for ARCv2 cores.

       -mfpu=fpu
           Enables support for specific floating-point hardware extensions for
           ARCv2 cores.  Supported values for fpu are:

           fpus
               Enables support for single-precision floating-point hardware
               extensions.

           fpud
               Enables support for double-precision floating-point hardware
               extensions.  The single-precision floating-point extension is
               also enabled.  Not available for ARC EM.

           fpuda
               Enables support for double-precision floating-point hardware
               extensions using double-precision assist instructions.  The
               single-precision floating-point extension is also enabled.  This
               option is only available for ARC EM.

           fpuda_div
               Enables support for double-precision floating-point hardware
               extensions using double-precision assist instructions.  The
               single-precision floating-point, square-root, and divide
               extensions are also enabled.  This option is only available for
               ARC EM.

           fpuda_fma
               Enables support for double-precision floating-point hardware
               extensions using double-precision assist instructions.  The
               single-precision floating-point and fused multiply and add
               hardware extensions are also enabled.  This option is only
               available for ARC EM.

           fpuda_all
               Enables support for double-precision floating-point hardware
               extensions using double-precision assist instructions.  All
               single-precision floating-point hardware extensions are also
               enabled.  This option is only available for ARC EM.

           fpus_div
               Enables support for single-precision floating-point, square-root
               and divide hardware extensions.

           fpud_div
               Enables support for double-precision floating-point, square-root
               and divide hardware extensions.  This option includes option
               fpus_div. Not available for ARC EM.

           fpus_fma
               Enables support for single-precision floating-point and fused
               multiply and add hardware extensions.

           fpud_fma
               Enables support for double-precision floating-point and fused
               multiply and add hardware extensions.  This option includes
               option fpus_fma.  Not available for ARC EM.

           fpus_all
               Enables support for all single-precision floating-point hardware
               extensions.

           fpud_all
               Enables support for all single- and double-precision floating-
               point hardware extensions.  Not available for ARC EM.

       -mirq-ctrl-saved=register-range, blink, lp_count
           Specifies general-purposes registers that the processor automatically
           saves/restores on interrupt entry and exit.  register-range is
           specified as two registers separated by a dash.  The register range
           always starts with "r0", the upper limit is "fp" register.  blink and
           lp_count are optional.  This option is only valid for ARC EM and ARC
           HS cores.

       -mrgf-banked-regs=number
           Specifies the number of registers replicated in second register bank
           on entry to fast interrupt.  Fast interrupts are interrupts with the
           highest priority level P0.  These interrupts save only PC and
           STATUS32 registers to avoid memory transactions during interrupt
           entry and exit sequences.  Use this option when you are using fast
           interrupts in an ARC V2 family processor.  Permitted values are 4, 8,
           16, and 32.

       -mlpc-width=width
           Specify the width of the "lp_count" register.  Valid values for width
           are 8, 16, 20, 24, 28 and 32 bits.  The default width is fixed to 32
           bits.  If the width is less than 32, the compiler does not attempt to
           transform loops in your program to use the zero-delay loop mechanism
           unless it is known that the "lp_count" register can hold the required
           loop-counter value.  Depending on the width specified, the compiler
           and run-time library might continue to use the loop mechanism for
           various needs.  This option defines macro "__ARC_LPC_WIDTH__" with
           the value of width.

       -mrf16
           This option instructs the compiler to generate code for a 16-entry
           register file.  This option defines the "__ARC_RF16__" preprocessor
           macro.

       -mbranch-index
           Enable use of "bi" or "bih" instructions to implement jump tables.

       The following options are passed through to the assembler, and also
       define preprocessor macro symbols.

       -mdsp-packa
           Passed down to the assembler to enable the DSP Pack A extensions.
           Also sets the preprocessor symbol "__Xdsp_packa".  This option is
           deprecated.

       -mdvbf
           Passed down to the assembler to enable the dual Viterbi butterfly
           extension.  Also sets the preprocessor symbol "__Xdvbf".  This option
           is deprecated.

       -mlock
           Passed down to the assembler to enable the locked load/store
           conditional extension.  Also sets the preprocessor symbol "__Xlock".

       -mmac-d16
           Passed down to the assembler.  Also sets the preprocessor symbol
           "__Xxmac_d16".  This option is deprecated.

       -mmac-24
           Passed down to the assembler.  Also sets the preprocessor symbol
           "__Xxmac_24".  This option is deprecated.

       -mrtsc
           Passed down to the assembler to enable the 64-bit time-stamp counter
           extension instruction.  Also sets the preprocessor symbol "__Xrtsc".
           This option is deprecated.

       -mswape
           Passed down to the assembler to enable the swap byte ordering
           extension instruction.  Also sets the preprocessor symbol "__Xswape".

       -mtelephony
           Passed down to the assembler to enable dual- and single-operand
           instructions for telephony.  Also sets the preprocessor symbol
           "__Xtelephony".  This option is deprecated.

       -mxy
           Passed down to the assembler to enable the XY memory extension.  Also
           sets the preprocessor symbol "__Xxy".

       The following options control how the assembly code is annotated:

       -misize
           Annotate assembler instructions with estimated addresses.

       -mannotate-align
           Explain what alignment considerations lead to the decision to make an
           instruction short or long.

       The following options are passed through to the linker:

       -marclinux
           Passed through to the linker, to specify use of the "arclinux"
           emulation.  This option is enabled by default in tool chains built
           for "arc-linux-uclibc" and "arceb-linux-uclibc" targets when
           profiling is not requested.

       -marclinux_prof
           Passed through to the linker, to specify use of the "arclinux_prof"
           emulation.  This option is enabled by default in tool chains built
           for "arc-linux-uclibc" and "arceb-linux-uclibc" targets when
           profiling is requested.

       The following options control the semantics of generated code:

       -mlong-calls
           Generate calls as register indirect calls, thus providing access to
           the full 32-bit address range.

       -mmedium-calls
           Don't use less than 25-bit addressing range for calls, which is the
           offset available for an unconditional branch-and-link instruction.
           Conditional execution of function calls is suppressed, to allow use
           of the 25-bit range, rather than the 21-bit range with conditional
           branch-and-link.  This is the default for tool chains built for
           "arc-linux-uclibc" and "arceb-linux-uclibc" targets.

       -G num
           Put definitions of externally-visible data in a small data section if
           that data is no bigger than num bytes.  The default value of num is 4
           for any ARC configuration, or 8 when we have double load/store
           operations.

       -mno-sdata
           Do not generate sdata references.  This is the default for tool
           chains built for "arc-linux-uclibc" and "arceb-linux-uclibc" targets.

       -mvolatile-cache
           Use ordinarily cached memory accesses for volatile references.  This
           is the default.

       -mno-volatile-cache
           Enable cache bypass for volatile references.

       The following options fine tune code generation:

       -malign-call
           Do alignment optimizations for call instructions.

       -mauto-modify-reg
           Enable the use of pre/post modify with register displacement.

       -mbbit-peephole
           Enable bbit peephole2.

       -mno-brcc
           This option disables a target-specific pass in arc_reorg to generate
           compare-and-branch ("brcc") instructions.  It has no effect on
           generation of these instructions driven by the combiner pass.

       -mcase-vector-pcrel
           Use PC-relative switch case tables to enable case table shortening.
           This is the default for -Os.

       -mcompact-casesi
           Enable compact "casesi" pattern.  This is the default for -Os, and
           only available for ARCv1 cores.  This option is deprecated.

       -mno-cond-exec
           Disable the ARCompact-specific pass to generate conditional execution
           instructions.

           Due to delay slot scheduling and interactions between operand
           numbers, literal sizes, instruction lengths, and the support for
           conditional execution, the target-independent pass to generate
           conditional execution is often lacking, so the ARC port has kept a
           special pass around that tries to find more conditional execution
           generation opportunities after register allocation, branch
           shortening, and delay slot scheduling have been done.  This pass
           generally, but not always, improves performance and code size, at the
           cost of extra compilation time, which is why there is an option to
           switch it off.  If you have a problem with call instructions
           exceeding their allowable offset range because they are
           conditionalized, you should consider using -mmedium-calls instead.

       -mearly-cbranchsi
           Enable pre-reload use of the "cbranchsi" pattern.

       -mexpand-adddi
           Expand "adddi3" and "subdi3" at RTL generation time into "add.f",
           "adc" etc.  This option is deprecated.

       -mindexed-loads
           Enable the use of indexed loads.  This can be problematic because
           some optimizers then assume that indexed stores exist, which is not
           the case.

       -mlra
           Enable Local Register Allocation.  This is still experimental for
           ARC, so by default the compiler uses standard reload (i.e. -mno-lra).

       -mlra-priority-none
           Don't indicate any priority for target registers.

       -mlra-priority-compact
           Indicate target register priority for r0..r3 / r12..r15.

       -mlra-priority-noncompact
           Reduce target register priority for r0..r3 / r12..r15.

       -mmillicode
           When optimizing for size (using -Os), prologues and epilogues that
           have to save or restore a large number of registers are often
           shortened by using call to a special function in libgcc; this is
           referred to as a millicode call.  As these calls can pose performance
           issues, and/or cause linking issues when linking in a nonstandard
           way, this option is provided to turn on or off millicode call
           generation.

       -mcode-density-frame
           This option enable the compiler to emit "enter" and "leave"
           instructions.  These instructions are only valid for CPUs with code-
           density feature.

       -mmixed-code
           Tweak register allocation to help 16-bit instruction generation.
           This generally has the effect of decreasing the average instruction
           size while increasing the instruction count.

       -mq-class
           Ths option is deprecated.  Enable q instruction alternatives.  This
           is the default for -Os.

       -mRcq
           Enable Rcq constraint handling.  Most short code generation depends
           on this.  This is the default.

       -mRcw
           Enable Rcw constraint handling.  Most ccfsm condexec mostly depends
           on this.  This is the default.

       -msize-level=level
           Fine-tune size optimization with regards to instruction lengths and
           alignment.  The recognized values for level are:

           0   No size optimization.  This level is deprecated and treated like
               1.

           1   Short instructions are used opportunistically.

           2   In addition, alignment of loops and of code after barriers are
               dropped.

           3   In addition, optional data alignment is dropped, and the option
               Os is enabled.

           This defaults to 3 when -Os is in effect.  Otherwise, the behavior
           when this is not set is equivalent to level 1.

       -mtune=cpu
           Set instruction scheduling parameters for cpu, overriding any implied
           by -mcpu=.

           Supported values for cpu are

           ARC600
               Tune for ARC600 CPU.

           ARC601
               Tune for ARC601 CPU.

           ARC700
               Tune for ARC700 CPU with standard multiplier block.

           ARC700-xmac
               Tune for ARC700 CPU with XMAC block.

           ARC725D
               Tune for ARC725D CPU.

           ARC750D
               Tune for ARC750D CPU.

       -mmultcost=num
           Cost to assume for a multiply instruction, with 4 being equal to a
           normal instruction.

       -munalign-prob-threshold=probability
           Set probability threshold for unaligning branches.  When tuning for
           ARC700 and optimizing for speed, branches without filled delay slot
           are preferably emitted unaligned and long, unless profiling indicates
           that the probability for the branch to be taken is below probability.
           The default is (REG_BR_PROB_BASE/2), i.e. 5000.

       The following options are maintained for backward compatibility, but are
       now deprecated and will be removed in a future release:

       -margonaut
           Obsolete FPX.

       -mbig-endian
       -EB Compile code for big-endian targets.  Use of these options is now
           deprecated.  Big-endian code is supported by configuring GCC to build
           "arceb-elf32" and "arceb-linux-uclibc" targets, for which big endian
           is the default.

       -mlittle-endian
       -EL Compile code for little-endian targets.  Use of these options is now
           deprecated.  Little-endian code is supported by configuring GCC to
           build "arc-elf32" and "arc-linux-uclibc" targets, for which little
           endian is the default.

       -mbarrel_shifter
           Replaced by -mbarrel-shifter.

       -mdpfp_compact
           Replaced by -mdpfp-compact.

       -mdpfp_fast
           Replaced by -mdpfp-fast.

       -mdsp_packa
           Replaced by -mdsp-packa.

       -mEA
           Replaced by -mea.

       -mmac_24
           Replaced by -mmac-24.

       -mmac_d16
           Replaced by -mmac-d16.

       -mspfp_compact
           Replaced by -mspfp-compact.

       -mspfp_fast
           Replaced by -mspfp-fast.

       -mtune=cpu
           Values arc600, arc601, arc700 and arc700-xmac for cpu are replaced by
           ARC600, ARC601, ARC700 and ARC700-xmac respectively.

       -multcost=num
           Replaced by -mmultcost.

       ARM Options

       These -m options are defined for the ARM port:

       -mabi=name
           Generate code for the specified ABI.  Permissible values are: apcs-
           gnu, atpcs, aapcs, aapcs-linux and iwmmxt.

       -mapcs-frame
           Generate a stack frame that is compliant with the ARM Procedure Call
           Standard for all functions, even if this is not strictly necessary
           for correct execution of the code.  Specifying -fomit-frame-pointer
           with this option causes the stack frames not to be generated for leaf
           functions.  The default is -mno-apcs-frame.  This option is
           deprecated.

       -mapcs
           This is a synonym for -mapcs-frame and is deprecated.

       -mthumb-interwork
           Generate code that supports calling between the ARM and Thumb
           instruction sets.  Without this option, on pre-v5 architectures, the
           two instruction sets cannot be reliably used inside one program.  The
           default is -mno-thumb-interwork, since slightly larger code is
           generated when -mthumb-interwork is specified.  In AAPCS
           configurations this option is meaningless.

       -mno-sched-prolog
           Prevent the reordering of instructions in the function prologue, or
           the merging of those instruction with the instructions in the
           function's body.  This means that all functions start with a
           recognizable set of instructions (or in fact one of a choice from a
           small set of different function prologues), and this information can
           be used to locate the start of functions inside an executable piece
           of code.  The default is -msched-prolog.

       -mfloat-abi=name
           Specifies which floating-point ABI to use.  Permissible values are:
           soft, softfp and hard.

           Specifying soft causes GCC to generate output containing library
           calls for floating-point operations.  softfp allows the generation of
           code using hardware floating-point instructions, but still uses the
           soft-float calling conventions.  hard allows generation of floating-
           point instructions and uses FPU-specific calling conventions.

           The default depends on the specific target configuration.  Note that
           the hard-float and soft-float ABIs are not link-compatible; you must
           compile your entire program with the same ABI, and link with a
           compatible set of libraries.

       -mgeneral-regs-only
           Generate code which uses only the general-purpose registers.  This
           will prevent the compiler from using floating-point and Advanced SIMD
           registers but will not impose any restrictions on the assembler.

       -mlittle-endian
           Generate code for a processor running in little-endian mode.  This is
           the default for all standard configurations.

       -mbig-endian
           Generate code for a processor running in big-endian mode; the default
           is to compile code for a little-endian processor.

       -mbe8
       -mbe32
           When linking a big-endian image select between BE8 and BE32 formats.
           The option has no effect for little-endian images and is ignored.
           The default is dependent on the selected target architecture.  For
           ARMv6 and later architectures the default is BE8, for older
           architectures the default is BE32.  BE32 format has been deprecated
           by ARM.

       -march=name[+extension...]
           This specifies the name of the target ARM architecture.  GCC uses
           this name to determine what kind of instructions it can emit when
           generating assembly code.  This option can be used in conjunction
           with or instead of the -mcpu= option.

           Permissible names are: armv4t, armv5t, armv5te, armv6, armv6j,
           armv6k, armv6kz, armv6t2, armv6z, armv6zk, armv7, armv7-a, armv7ve,
           armv8-a, armv8.1-a, armv8.2-a, armv8.3-a, armv8.4-a, armv8.5-a,
           armv8.6-a, armv7-r, armv8-r, armv6-m, armv6s-m, armv7-m, armv7e-m,
           armv8-m.base, armv8-m.main, armv8.1-m.main, iwmmxt and iwmmxt2.

           Additionally, the following architectures, which lack support for the
           Thumb execution state, are recognized but support is deprecated:
           armv4.

           Many of the architectures support extensions.  These can be added by
           appending +extension to the architecture name.  Extension options are
           processed in order and capabilities accumulate.  An extension will
           also enable any necessary base extensions upon which it depends.  For
           example, the +crypto extension will always enable the +simd
           extension.  The exception to the additive construction is for
           extensions that are prefixed with +no...: these extensions disable
           the specified option and any other extensions that may depend on the
           presence of that extension.

           For example, -march=armv7-a+simd+nofp+vfpv4 is equivalent to writing
           -march=armv7-a+vfpv4 since the +simd option is entirely disabled by
           the +nofp option that follows it.

           Most extension names are generically named, but have an effect that
           is dependent upon the architecture to which it is applied.  For
           example, the +simd option can be applied to both armv7-a and armv8-a
           architectures, but will enable the original ARMv7-A Advanced SIMD
           (Neon) extensions for armv7-a and the ARMv8-A variant for armv8-a.

           The table below lists the supported extensions for each architecture.
           Architectures not mentioned do not support any extensions.

           armv5te
           armv6
           armv6j
           armv6k
           armv6kz
           armv6t2
           armv6z
           armv6zk
               +fp The VFPv2 floating-point instructions.  The extension +vfpv2
                   can be used as an alias for this extension.

               +nofp
                   Disable the floating-point instructions.

           armv7
               The common subset of the ARMv7-A, ARMv7-R and ARMv7-M
               architectures.

               +fp The VFPv3 floating-point instructions, with 16 double-
                   precision registers.  The extension +vfpv3-d16 can be used as
                   an alias for this extension.  Note that floating-point is not
                   supported by the base ARMv7-M architecture, but is compatible
                   with both the ARMv7-A and ARMv7-R architectures.

               +nofp
                   Disable the floating-point instructions.

           armv7-a
               +mp The multiprocessing extension.

               +sec
                   The security extension.

               +fp The VFPv3 floating-point instructions, with 16 double-
                   precision registers.  The extension +vfpv3-d16 can be used as
                   an alias for this extension.

               +simd
                   The Advanced SIMD (Neon) v1 and the VFPv3 floating-point
                   instructions.  The extensions +neon and +neon-vfpv3 can be
                   used as aliases for this extension.

               +vfpv3
                   The VFPv3 floating-point instructions, with 32 double-
                   precision registers.

               +vfpv3-d16-fp16
                   The VFPv3 floating-point instructions, with 16 double-
                   precision registers and the half-precision floating-point
                   conversion operations.

               +vfpv3-fp16
                   The VFPv3 floating-point instructions, with 32 double-
                   precision registers and the half-precision floating-point
                   conversion operations.

               +vfpv4-d16
                   The VFPv4 floating-point instructions, with 16 double-
                   precision registers.

               +vfpv4
                   The VFPv4 floating-point instructions, with 32 double-
                   precision registers.

               +neon-fp16
                   The Advanced SIMD (Neon) v1 and the VFPv3 floating-point
                   instructions, with the half-precision floating-point
                   conversion operations.

               +neon-vfpv4
                   The Advanced SIMD (Neon) v2 and the VFPv4 floating-point
                   instructions.

               +nosimd
                   Disable the Advanced SIMD instructions (does not disable
                   floating point).

               +nofp
                   Disable the floating-point and Advanced SIMD instructions.

           armv7ve
               The extended version of the ARMv7-A architecture with support for
               virtualization.

               +fp The VFPv4 floating-point instructions, with 16 double-
                   precision registers.  The extension +vfpv4-d16 can be used as
                   an alias for this extension.

               +simd
                   The Advanced SIMD (Neon) v2 and the VFPv4 floating-point
                   instructions.  The extension +neon-vfpv4 can be used as an
                   alias for this extension.

               +vfpv3-d16
                   The VFPv3 floating-point instructions, with 16 double-
                   precision registers.

               +vfpv3
                   The VFPv3 floating-point instructions, with 32 double-
                   precision registers.

               +vfpv3-d16-fp16
                   The VFPv3 floating-point instructions, with 16 double-
                   precision registers and the half-precision floating-point
                   conversion operations.

               +vfpv3-fp16
                   The VFPv3 floating-point instructions, with 32 double-
                   precision registers and the half-precision floating-point
                   conversion operations.

               +vfpv4-d16
                   The VFPv4 floating-point instructions, with 16 double-
                   precision registers.

               +vfpv4
                   The VFPv4 floating-point instructions, with 32 double-
                   precision registers.

               +neon
                   The Advanced SIMD (Neon) v1 and the VFPv3 floating-point
                   instructions.  The extension +neon-vfpv3 can be used as an
                   alias for this extension.

               +neon-fp16
                   The Advanced SIMD (Neon) v1 and the VFPv3 floating-point
                   instructions, with the half-precision floating-point
                   conversion operations.

               +nosimd
                   Disable the Advanced SIMD instructions (does not disable
                   floating point).

               +nofp
                   Disable the floating-point and Advanced SIMD instructions.

           armv8-a
               +crc
                   The Cyclic Redundancy Check (CRC) instructions.

               +simd
                   The ARMv8-A Advanced SIMD and floating-point instructions.

               +crypto
                   The cryptographic instructions.

               +nocrypto
                   Disable the cryptographic instructions.

               +nofp
                   Disable the floating-point, Advanced SIMD and cryptographic
                   instructions.

               +sb Speculation Barrier Instruction.

               +predres
                   Execution and Data Prediction Restriction Instructions.

           armv8.1-a
               +simd
                   The ARMv8.1-A Advanced SIMD and floating-point instructions.

               +crypto
                   The cryptographic instructions.  This also enables the
                   Advanced SIMD and floating-point instructions.

               +nocrypto
                   Disable the cryptographic instructions.

               +nofp
                   Disable the floating-point, Advanced SIMD and cryptographic
                   instructions.

               +sb Speculation Barrier Instruction.

               +predres
                   Execution and Data Prediction Restriction Instructions.

           armv8.2-a
           armv8.3-a
               +fp16
                   The half-precision floating-point data processing
                   instructions.  This also enables the Advanced SIMD and
                   floating-point instructions.

               +fp16fml
                   The half-precision floating-point fmla extension.  This also
                   enables the half-precision floating-point extension and
                   Advanced SIMD and floating-point instructions.

               +simd
                   The ARMv8.1-A Advanced SIMD and floating-point instructions.

               +crypto
                   The cryptographic instructions.  This also enables the
                   Advanced SIMD and floating-point instructions.

               +dotprod
                   Enable the Dot Product extension.  This also enables Advanced
                   SIMD instructions.

               +nocrypto
                   Disable the cryptographic extension.

               +nofp
                   Disable the floating-point, Advanced SIMD and cryptographic
                   instructions.

               +sb Speculation Barrier Instruction.

               +predres
                   Execution and Data Prediction Restriction Instructions.

               +i8mm
                   8-bit Integer Matrix Multiply instructions.  This also
                   enables Advanced SIMD and floating-point instructions.

               +bf16
                   Brain half-precision floating-point instructions.  This also
                   enables Advanced SIMD and floating-point instructions.

           armv8.4-a
               +fp16
                   The half-precision floating-point data processing
                   instructions.  This also enables the Advanced SIMD and
                   floating-point instructions as well as the Dot Product
                   extension and the half-precision floating-point fmla
                   extension.

               +simd
                   The ARMv8.3-A Advanced SIMD and floating-point instructions
                   as well as the Dot Product extension.

               +crypto
                   The cryptographic instructions.  This also enables the
                   Advanced SIMD and floating-point instructions as well as the
                   Dot Product extension.

               +nocrypto
                   Disable the cryptographic extension.

               +nofp
                   Disable the floating-point, Advanced SIMD and cryptographic
                   instructions.

               +sb Speculation Barrier Instruction.

               +predres
                   Execution and Data Prediction Restriction Instructions.

               +i8mm
                   8-bit Integer Matrix Multiply instructions.  This also
                   enables Advanced SIMD and floating-point instructions.

               +bf16
                   Brain half-precision floating-point instructions.  This also
                   enables Advanced SIMD and floating-point instructions.

           armv8.5-a
               +fp16
                   The half-precision floating-point data processing
                   instructions.  This also enables the Advanced SIMD and
                   floating-point instructions as well as the Dot Product
                   extension and the half-precision floating-point fmla
                   extension.

               +simd
                   The ARMv8.3-A Advanced SIMD and floating-point instructions
                   as well as the Dot Product extension.

               +crypto
                   The cryptographic instructions.  This also enables the
                   Advanced SIMD and floating-point instructions as well as the
                   Dot Product extension.

               +nocrypto
                   Disable the cryptographic extension.

               +nofp
                   Disable the floating-point, Advanced SIMD and cryptographic
                   instructions.

               +i8mm
                   8-bit Integer Matrix Multiply instructions.  This also
                   enables Advanced SIMD and floating-point instructions.

               +bf16
                   Brain half-precision floating-point instructions.  This also
                   enables Advanced SIMD and floating-point instructions.

           armv8.6-a
               +fp16
                   The half-precision floating-point data processing
                   instructions.  This also enables the Advanced SIMD and
                   floating-point instructions as well as the Dot Product
                   extension and the half-precision floating-point fmla
                   extension.

               +simd
                   The ARMv8.3-A Advanced SIMD and floating-point instructions
                   as well as the Dot Product extension.

               +crypto
                   The cryptographic instructions.  This also enables the
                   Advanced SIMD and floating-point instructions as well as the
                   Dot Product extension.

               +nocrypto
                   Disable the cryptographic extension.

               +nofp
                   Disable the floating-point, Advanced SIMD and cryptographic
                   instructions.

               +i8mm
                   8-bit Integer Matrix Multiply instructions.  This also
                   enables Advanced SIMD and floating-point instructions.

               +bf16
                   Brain half-precision floating-point instructions.  This also
                   enables Advanced SIMD and floating-point instructions.

           armv7-r
               +fp.sp
                   The single-precision VFPv3 floating-point instructions.  The
                   extension +vfpv3xd can be used as an alias for this
                   extension.

               +fp The VFPv3 floating-point instructions with 16 double-
                   precision registers.  The extension +vfpv3-d16 can be used as
                   an alias for this extension.

               +vfpv3xd-d16-fp16
                   The single-precision VFPv3 floating-point instructions with
                   16 double-precision registers and the half-precision
                   floating-point conversion operations.

               +vfpv3-d16-fp16
                   The VFPv3 floating-point instructions with 16 double-
                   precision registers and the half-precision floating-point
                   conversion operations.

               +nofp
                   Disable the floating-point extension.

               +idiv
                   The ARM-state integer division instructions.

               +noidiv
                   Disable the ARM-state integer division extension.

           armv7e-m
               +fp The single-precision VFPv4 floating-point instructions.

               +fpv5
                   The single-precision FPv5 floating-point instructions.

               +fp.dp
                   The single- and double-precision FPv5 floating-point
                   instructions.

               +nofp
                   Disable the floating-point extensions.

           armv8.1-m.main
               +dsp
                   The DSP instructions.

               +mve
                   The M-Profile Vector Extension (MVE) integer instructions.

               +mve.fp
                   The M-Profile Vector Extension (MVE) integer and single
                   precision floating-point instructions.

               +fp The single-precision floating-point instructions.

               +fp.dp
                   The single- and double-precision floating-point instructions.

               +nofp
                   Disable the floating-point extension.

               +cdecp0, +cdecp1, ... , +cdecp7
                   Enable the Custom Datapath Extension (CDE) on selected
                   coprocessors according to the numbers given in the options in
                   the range 0 to 7.

           armv8-m.main
               +dsp
                   The DSP instructions.

               +nodsp
                   Disable the DSP extension.

               +fp The single-precision floating-point instructions.

               +fp.dp
                   The single- and double-precision floating-point instructions.

               +nofp
                   Disable the floating-point extension.

               +cdecp0, +cdecp1, ... , +cdecp7
                   Enable the Custom Datapath Extension (CDE) on selected
                   coprocessors according to the numbers given in the options in
                   the range 0 to 7.

           armv8-r
               +crc
                   The Cyclic Redundancy Check (CRC) instructions.

               +fp.sp
                   The single-precision FPv5 floating-point instructions.

               +simd
                   The ARMv8-A Advanced SIMD and floating-point instructions.

               +crypto
                   The cryptographic instructions.

               +nocrypto
                   Disable the cryptographic instructions.

               +nofp
                   Disable the floating-point, Advanced SIMD and cryptographic
                   instructions.

           -march=native causes the compiler to auto-detect the architecture of
           the build computer.  At present, this feature is only supported on
           GNU/Linux, and not all architectures are recognized.  If the auto-
           detect is unsuccessful the option has no effect.

       -mtune=name
           This option specifies the name of the target ARM processor for which
           GCC should tune the performance of the code.  For some ARM
           implementations better performance can be obtained by using this
           option.  Permissible names are: arm7tdmi, arm7tdmi-s, arm710t,
           arm720t, arm740t, strongarm, strongarm110, strongarm1100,
           0strongarm1110, arm8, arm810, arm9, arm9e, arm920, arm920t, arm922t,
           arm946e-s, arm966e-s, arm968e-s, arm926ej-s, arm940t, arm9tdmi,
           arm10tdmi, arm1020t, arm1026ej-s, arm10e, arm1020e, arm1022e,
           arm1136j-s, arm1136jf-s, mpcore, mpcorenovfp, arm1156t2-s,
           arm1156t2f-s, arm1176jz-s, arm1176jzf-s, generic-armv7-a, cortex-a5,
           cortex-a7, cortex-a8, cortex-a9, cortex-a12, cortex-a15, cortex-a17,
           cortex-a32, cortex-a35, cortex-a53, cortex-a55, cortex-a57,
           cortex-a72, cortex-a73, cortex-a75, cortex-a76, cortex-a76ae,
           cortex-a77, cortex-a78, cortex-a78ae, cortex-a78c, ares, cortex-r4,
           cortex-r4f, cortex-r5, cortex-r7, cortex-r8, cortex-r52, cortex-m0,
           cortex-m0plus, cortex-m1, cortex-m3, cortex-m4, cortex-m7,
           cortex-m23, cortex-m33, cortex-m35p, cortex-m55, cortex-x1,
           cortex-m1.small-multiply, cortex-m0.small-multiply,
           cortex-m0plus.small-multiply, exynos-m1, marvell-pj4, neoverse-n1,
           neoverse-n2, neoverse-v1, xscale, iwmmxt, iwmmxt2, ep9312, fa526,
           fa626, fa606te, fa626te, fmp626, fa726te, xgene1.

           Additionally, this option can specify that GCC should tune the
           performance of the code for a big.LITTLE system.  Permissible names
           are: cortex-a15.cortex-a7, cortex-a17.cortex-a7,
           cortex-a57.cortex-a53, cortex-a72.cortex-a53, cortex-a72.cortex-a35,
           cortex-a73.cortex-a53, cortex-a75.cortex-a55, cortex-a76.cortex-a55.

           -mtune=generic-arch specifies that GCC should tune the performance
           for a blend of processors within architecture arch.  The aim is to
           generate code that run well on the current most popular processors,
           balancing between optimizations that benefit some CPUs in the range,
           and avoiding performance pitfalls of other CPUs.  The effects of this
           option may change in future GCC versions as CPU models come and go.

           -mtune permits the same extension options as -mcpu, but the extension
           options do not affect the tuning of the generated code.

           -mtune=native causes the compiler to auto-detect the CPU of the build
           computer.  At present, this feature is only supported on GNU/Linux,
           and not all architectures are recognized.  If the auto-detect is
           unsuccessful the option has no effect.

       -mcpu=name[+extension...]
           This specifies the name of the target ARM processor.  GCC uses this
           name to derive the name of the target ARM architecture (as if
           specified by -march) and the ARM processor type for which to tune for
           performance (as if specified by -mtune).  Where this option is used
           in conjunction with -march or -mtune, those options take precedence
           over the appropriate part of this option.

           Many of the supported CPUs implement optional architectural
           extensions.  Where this is so the architectural extensions are
           normally enabled by default.  If implementations that lack the
           extension exist, then the extension syntax can be used to disable
           those extensions that have been omitted.  For floating-point and
           Advanced SIMD (Neon) instructions, the settings of the options
           -mfloat-abi and -mfpu must also be considered: floating-point and
           Advanced SIMD instructions will only be used if -mfloat-abi is not
           set to soft; and any setting of -mfpu other than auto will override
           the available floating-point and SIMD extension instructions.

           For example, cortex-a9 can be found in three major configurations:
           integer only, with just a floating-point unit or with floating-point
           and Advanced SIMD.  The default is to enable all the instructions,
           but the extensions +nosimd and +nofp can be used to disable just the
           SIMD or both the SIMD and floating-point instructions respectively.

           Permissible names for this option are the same as those for -mtune.

           The following extension options are common to the listed CPUs:

           +nodsp
               Disable the DSP instructions on cortex-m33, cortex-m35p.

           +nofp
               Disables the floating-point instructions on arm9e, arm946e-s,
               arm966e-s, arm968e-s, arm10e, arm1020e, arm1022e, arm926ej-s,
               arm1026ej-s, cortex-r5, cortex-r7, cortex-r8, cortex-m4,
               cortex-m7, cortex-m33 and cortex-m35p.  Disables the floating-
               point and SIMD instructions on generic-armv7-a, cortex-a5,
               cortex-a7, cortex-a8, cortex-a9, cortex-a12, cortex-a15,
               cortex-a17, cortex-a15.cortex-a7, cortex-a17.cortex-a7,
               cortex-a32, cortex-a35, cortex-a53 and cortex-a55.

           +nofp.dp
               Disables the double-precision component of the floating-point
               instructions on cortex-r5, cortex-r7, cortex-r8, cortex-r52 and
               cortex-m7.

           +nosimd
               Disables the SIMD (but not floating-point) instructions on
               generic-armv7-a, cortex-a5, cortex-a7 and cortex-a9.

           +crypto
               Enables the cryptographic instructions on cortex-a32, cortex-a35,
               cortex-a53, cortex-a55, cortex-a57, cortex-a72, cortex-a73,
               cortex-a75, exynos-m1, xgene1, cortex-a57.cortex-a53,
               cortex-a72.cortex-a53, cortex-a73.cortex-a35,
               cortex-a73.cortex-a53 and cortex-a75.cortex-a55.

           Additionally the generic-armv7-a pseudo target defaults to VFPv3 with
           16 double-precision registers.  It supports the following extension
           options: mp, sec, vfpv3-d16, vfpv3, vfpv3-d16-fp16, vfpv3-fp16,
           vfpv4-d16, vfpv4, neon, neon-vfpv3, neon-fp16, neon-vfpv4.  The
           meanings are the same as for the extensions to -march=armv7-a.

           -mcpu=generic-arch is also permissible, and is equivalent to
           -march=arch -mtune=generic-arch.  See -mtune for more information.

           -mcpu=native causes the compiler to auto-detect the CPU of the build
           computer.  At present, this feature is only supported on GNU/Linux,
           and not all architectures are recognized.  If the auto-detect is
           unsuccessful the option has no effect.

       -mfpu=name
           This specifies what floating-point hardware (or hardware emulation)
           is available on the target.  Permissible names are: auto, vfpv2,
           vfpv3, vfpv3-fp16, vfpv3-d16, vfpv3-d16-fp16, vfpv3xd, vfpv3xd-fp16,
           neon-vfpv3, neon-fp16, vfpv4, vfpv4-d16, fpv4-sp-d16, neon-vfpv4,
           fpv5-d16, fpv5-sp-d16, fp-armv8, neon-fp-armv8 and
           crypto-neon-fp-armv8.  Note that neon is an alias for neon-vfpv3 and
           vfp is an alias for vfpv2.

           The setting auto is the default and is special.  It causes the
           compiler to select the floating-point and Advanced SIMD instructions
           based on the settings of -mcpu and -march.

           If the selected floating-point hardware includes the NEON extension
           (e.g. -mfpu=neon), note that floating-point operations are not
           generated by GCC's auto-vectorization pass unless
           -funsafe-math-optimizations is also specified.  This is because NEON
           hardware does not fully implement the IEEE 754 standard for floating-
           point arithmetic (in particular denormal values are treated as zero),
           so the use of NEON instructions may lead to a loss of precision.

           You can also set the fpu name at function level by using the
           "target("fpu=")" function attributes or pragmas.

       -mfp16-format=name
           Specify the format of the "__fp16" half-precision floating-point
           type.  Permissible names are none, ieee, and alternative; the default
           is none, in which case the "__fp16" type is not defined.

       -mstructure-size-boundary=n
           The sizes of all structures and unions are rounded up to a multiple
           of the number of bits set by this option.  Permissible values are 8,
           32 and 64.  The default value varies for different toolchains.  For
           the COFF targeted toolchain the default value is 8.  A value of 64 is
           only allowed if the underlying ABI supports it.

           Specifying a larger number can produce faster, more efficient code,
           but can also increase the size of the program.  Different values are
           potentially incompatible.  Code compiled with one value cannot
           necessarily expect to work with code or libraries compiled with
           another value, if they exchange information using structures or
           unions.

           This option is deprecated.

       -mabort-on-noreturn
           Generate a call to the function "abort" at the end of a "noreturn"
           function.  It is executed if the function tries to return.

       -mlong-calls
       -mno-long-calls
           Tells the compiler to perform function calls by first loading the
           address of the function into a register and then performing a
           subroutine call on this register.  This switch is needed if the
           target function lies outside of the 64-megabyte addressing range of
           the offset-based version of subroutine call instruction.

           Even if this switch is enabled, not all function calls are turned
           into long calls.  The heuristic is that static functions, functions
           that have the "short_call" attribute, functions that are inside the
           scope of a "#pragma no_long_calls" directive, and functions whose
           definitions have already been compiled within the current compilation
           unit are not turned into long calls.  The exceptions to this rule are
           that weak function definitions, functions with the "long_call"
           attribute or the "section" attribute, and functions that are within
           the scope of a "#pragma long_calls" directive are always turned into
           long calls.

           This feature is not enabled by default.  Specifying -mno-long-calls
           restores the default behavior, as does placing the function calls
           within the scope of a "#pragma long_calls_off" directive.  Note these
           switches have no effect on how the compiler generates code to handle
           function calls via function pointers.

       -msingle-pic-base
           Treat the register used for PIC addressing as read-only, rather than
           loading it in the prologue for each function.  The runtime system is
           responsible for initializing this register with an appropriate value
           before execution begins.

       -mpic-register=reg
           Specify the register to be used for PIC addressing.  For standard PIC
           base case, the default is any suitable register determined by
           compiler.  For single PIC base case, the default is R9 if target is
           EABI based or stack-checking is enabled, otherwise the default is
           R10.

       -mpic-data-is-text-relative
           Assume that the displacement between the text and data segments is
           fixed at static link time.  This permits using PC-relative addressing
           operations to access data known to be in the data segment.  For non-
           VxWorks RTP targets, this option is enabled by default.  When
           disabled on such targets, it will enable -msingle-pic-base by
           default.

       -mpoke-function-name
           Write the name of each function into the text section, directly
           preceding the function prologue.  The generated code is similar to
           this:

                        t0
                            .ascii "arm_poke_function_name", 0
                            .align
                        t1
                            .word 0xff000000 + (t1 - t0)
                        arm_poke_function_name
                            mov     ip, sp
                            stmfd   sp!, {fp, ip, lr, pc}
                            sub     fp, ip, #4

           When performing a stack backtrace, code can inspect the value of "pc"
           stored at "fp + 0".  If the trace function then looks at location "pc
           - 12" and the top 8 bits are set, then we know that there is a
           function name embedded immediately preceding this location and has
           length "((pc[-3]) & 0xff000000)".

       -mthumb
       -marm
           Select between generating code that executes in ARM and Thumb states.
           The default for most configurations is to generate code that executes
           in ARM state, but the default can be changed by configuring GCC with
           the --with-mode=state configure option.

           You can also override the ARM and Thumb mode for each function by
           using the "target("thumb")" and "target("arm")" function attributes
           or pragmas.

       -mflip-thumb
           Switch ARM/Thumb modes on alternating functions.  This option is
           provided for regression testing of mixed Thumb/ARM code generation,
           and is not intended for ordinary use in compiling code.

       -mtpcs-frame
           Generate a stack frame that is compliant with the Thumb Procedure
           Call Standard for all non-leaf functions.  (A leaf function is one
           that does not call any other functions.)  The default is
           -mno-tpcs-frame.

       -mtpcs-leaf-frame
           Generate a stack frame that is compliant with the Thumb Procedure
           Call Standard for all leaf functions.  (A leaf function is one that
           does not call any other functions.)  The default is
           -mno-apcs-leaf-frame.

       -mcallee-super-interworking
           Gives all externally visible functions in the file being compiled an
           ARM instruction set header which switches to Thumb mode before
           executing the rest of the function.  This allows these functions to
           be called from non-interworking code.  This option is not valid in
           AAPCS configurations because interworking is enabled by default.

       -mcaller-super-interworking
           Allows calls via function pointers (including virtual functions) to
           execute correctly regardless of whether the target code has been
           compiled for interworking or not.  There is a small overhead in the
           cost of executing a function pointer if this option is enabled.  This
           option is not valid in AAPCS configurations because interworking is
           enabled by default.

       -mtp=name
           Specify the access model for the thread local storage pointer.  The
           valid models are soft, which generates calls to "__aeabi_read_tp",
           cp15, which fetches the thread pointer from "cp15" directly
           (supported in the arm6k architecture), and auto, which uses the best
           available method for the selected processor.  The default setting is
           auto.

       -mtls-dialect=dialect
           Specify the dialect to use for accessing thread local storage.  Two
           dialects are supported---gnu and gnu2.  The gnu dialect selects the
           original GNU scheme for supporting local and global dynamic TLS
           models.  The gnu2 dialect selects the GNU descriptor scheme, which
           provides better performance for shared libraries.  The GNU descriptor
           scheme is compatible with the original scheme, but does require new
           assembler, linker and library support.  Initial and local exec TLS
           models are unaffected by this option and always use the original
           scheme.

       -mword-relocations
           Only generate absolute relocations on word-sized values (i.e.
           R_ARM_ABS32).  This is enabled by default on targets (uClinux,
           SymbianOS) where the runtime loader imposes this restriction, and
           when -fpic or -fPIC is specified. This option conflicts with
           -mslow-flash-data.

       -mfix-cortex-m3-ldrd
           Some Cortex-M3 cores can cause data corruption when "ldrd"
           instructions with overlapping destination and base registers are
           used.  This option avoids generating these instructions.  This option
           is enabled by default when -mcpu=cortex-m3 is specified.

       -munaligned-access
       -mno-unaligned-access
           Enables (or disables) reading and writing of 16- and 32- bit values
           from addresses that are not 16- or 32- bit aligned.  By default
           unaligned access is disabled for all pre-ARMv6, all ARMv6-M and for
           ARMv8-M Baseline architectures, and enabled for all other
           architectures.  If unaligned access is not enabled then words in
           packed data structures are accessed a byte at a time.

           The ARM attribute "Tag_CPU_unaligned_access" is set in the generated
           object file to either true or false, depending upon the setting of
           this option.  If unaligned access is enabled then the preprocessor
           symbol "__ARM_FEATURE_UNALIGNED" is also defined.

       -mneon-for-64bits
           This option is deprecated and has no effect.

       -mslow-flash-data
           Assume loading data from flash is slower than fetching instruction.
           Therefore literal load is minimized for better performance.  This
           option is only supported when compiling for ARMv7 M-profile and off
           by default. It conflicts with -mword-relocations.

       -masm-syntax-unified
           Assume inline assembler is using unified asm syntax.  The default is
           currently off which implies divided syntax.  This option has no
           impact on Thumb2. However, this may change in future releases of GCC.
           Divided syntax should be considered deprecated.

       -mrestrict-it
           Restricts generation of IT blocks to conform to the rules of ARMv8-A.
           IT blocks can only contain a single 16-bit instruction from a select
           set of instructions. This option is on by default for ARMv8-A Thumb
           mode.

       -mprint-tune-info
           Print CPU tuning information as comment in assembler file.  This is
           an option used only for regression testing of the compiler and not
           intended for ordinary use in compiling code.  This option is disabled
           by default.

       -mverbose-cost-dump
           Enable verbose cost model dumping in the debug dump files.  This
           option is provided for use in debugging the compiler.

       -mpure-code
           Do not allow constant data to be placed in code sections.
           Additionally, when compiling for ELF object format give all text
           sections the ELF processor-specific section attribute
           "SHF_ARM_PURECODE".  This option is only available when generating
           non-pic code for M-profile targets.

       -mcmse
           Generate secure code as per the "ARMv8-M Security Extensions:
           Requirements on Development Tools Engineering Specification", which
           can be found on
           <https://developer.arm.com/documentation/ecm0359818/latest/>.

       -mfdpic
       -mno-fdpic
           Select the FDPIC ABI, which uses 64-bit function descriptors to
           represent pointers to functions.  When the compiler is configured for
           "arm-*-uclinuxfdpiceabi" targets, this option is on by default and
           implies -fPIE if none of the PIC/PIE-related options is provided.  On
           other targets, it only enables the FDPIC-specific code generation
           features, and the user should explicitly provide the PIC/PIE-related
           options as needed.

           Note that static linking is not supported because it would still
           involve the dynamic linker when the program self-relocates.  If such
           behavior is acceptable, use -static and -Wl,-dynamic-linker options.

           The opposite -mno-fdpic option is useful (and required) to build the
           Linux kernel using the same ("arm-*-uclinuxfdpiceabi") toolchain as
           the one used to build the userland programs.

       AVR Options

       These options are defined for AVR implementations:

       -mmcu=mcu
           Specify Atmel AVR instruction set architectures (ISA) or MCU type.

           The default for this option is avr2.

           GCC supports the following AVR devices and ISAs:

           "avr2"
               "Classic" devices with up to 8 KiB of program memory.  mcu =
               "attiny22", "attiny26", "at90s2313", "at90s2323", "at90s2333",
               "at90s2343", "at90s4414", "at90s4433", "at90s4434", "at90c8534",
               "at90s8515", "at90s8535".

           "avr25"
               "Classic" devices with up to 8 KiB of program memory and with the
               "MOVW" instruction.  mcu = "attiny13", "attiny13a", "attiny24",
               "attiny24a", "attiny25", "attiny261", "attiny261a", "attiny2313",
               "attiny2313a", "attiny43u", "attiny44", "attiny44a", "attiny45",
               "attiny48", "attiny441", "attiny461", "attiny461a", "attiny4313",
               "attiny84", "attiny84a", "attiny85", "attiny87", "attiny88",
               "attiny828", "attiny841", "attiny861", "attiny861a", "ata5272",
               "ata6616c", "at86rf401".

           "avr3"
               "Classic" devices with 16 KiB up to 64 KiB of program memory.
               mcu = "at76c711", "at43usb355".

           "avr31"
               "Classic" devices with 128 KiB of program memory.  mcu =
               "atmega103", "at43usb320".

           "avr35"
               "Classic" devices with 16 KiB up to 64 KiB of program memory and
               with the "MOVW" instruction.  mcu = "attiny167", "attiny1634",
               "atmega8u2", "atmega16u2", "atmega32u2", "ata5505", "ata6617c",
               "ata664251", "at90usb82", "at90usb162".

           "avr4"
               "Enhanced" devices with up to 8 KiB of program memory.  mcu =
               "atmega48", "atmega48a", "atmega48p", "atmega48pa", "atmega48pb",
               "atmega8", "atmega8a", "atmega8hva", "atmega88", "atmega88a",
               "atmega88p", "atmega88pa", "atmega88pb", "atmega8515",
               "atmega8535", "ata6285", "ata6286", "ata6289", "ata6612c",
               "at90pwm1", "at90pwm2", "at90pwm2b", "at90pwm3", "at90pwm3b",
               "at90pwm81".

           "avr5"
               "Enhanced" devices with 16 KiB up to 64 KiB of program memory.
               mcu = "atmega16", "atmega16a", "atmega16hva", "atmega16hva2",
               "atmega16hvb", "atmega16hvbrevb", "atmega16m1", "atmega16u4",
               "atmega161", "atmega162", "atmega163", "atmega164a",
               "atmega164p", "atmega164pa", "atmega165", "atmega165a",
               "atmega165p", "atmega165pa", "atmega168", "atmega168a",
               "atmega168p", "atmega168pa", "atmega168pb", "atmega169",
               "atmega169a", "atmega169p", "atmega169pa", "atmega32",
               "atmega32a", "atmega32c1", "atmega32hvb", "atmega32hvbrevb",
               "atmega32m1", "atmega32u4", "atmega32u6", "atmega323",
               "atmega324a", "atmega324p", "atmega324pa", "atmega325",
               "atmega325a", "atmega325p", "atmega325pa", "atmega328",
               "atmega328p", "atmega328pb", "atmega329", "atmega329a",
               "atmega329p", "atmega329pa", "atmega3250", "atmega3250a",
               "atmega3250p", "atmega3250pa", "atmega3290", "atmega3290a",
               "atmega3290p", "atmega3290pa", "atmega406", "atmega64",
               "atmega64a", "atmega64c1", "atmega64hve", "atmega64hve2",
               "atmega64m1", "atmega64rfr2", "atmega640", "atmega644",
               "atmega644a", "atmega644p", "atmega644pa", "atmega644rfr2",
               "atmega645", "atmega645a", "atmega645p", "atmega649",
               "atmega649a", "atmega649p", "atmega6450", "atmega6450a",
               "atmega6450p", "atmega6490", "atmega6490a", "atmega6490p",
               "ata5795", "ata5790", "ata5790n", "ata5791", "ata6613c",
               "ata6614q", "ata5782", "ata5831", "ata8210", "ata8510",
               "ata5702m322", "at90pwm161", "at90pwm216", "at90pwm316",
               "at90can32", "at90can64", "at90scr100", "at90usb646",
               "at90usb647", "at94k", "m3000".

           "avr51"
               "Enhanced" devices with 128 KiB of program memory.  mcu =
               "atmega128", "atmega128a", "atmega128rfa1", "atmega128rfr2",
               "atmega1280", "atmega1281", "atmega1284", "atmega1284p",
               "atmega1284rfr2", "at90can128", "at90usb1286", "at90usb1287".

           "avr6"
               "Enhanced" devices with 3-byte PC, i.e. with more than 128 KiB of
               program memory.  mcu = "atmega256rfr2", "atmega2560",
               "atmega2561", "atmega2564rfr2".

           "avrxmega2"
               "XMEGA" devices with more than 8 KiB and up to 64 KiB of program
               memory.  mcu = "atxmega8e5", "atxmega16a4", "atxmega16a4u",
               "atxmega16c4", "atxmega16d4", "atxmega16e5", "atxmega32a4",
               "atxmega32a4u", "atxmega32c3", "atxmega32c4", "atxmega32d3",
               "atxmega32d4", "atxmega32e5".

           "avrxmega3"
               "XMEGA" devices with up to 64 KiB of combined program memory and
               RAM, and with program memory visible in the RAM address space.
               mcu = "attiny202", "attiny204", "attiny212", "attiny214",
               "attiny402", "attiny404", "attiny406", "attiny412", "attiny414",
               "attiny416", "attiny417", "attiny804", "attiny806", "attiny807",
               "attiny814", "attiny816", "attiny817", "attiny1604",
               "attiny1606", "attiny1607", "attiny1614", "attiny1616",
               "attiny1617", "attiny3214", "attiny3216", "attiny3217",
               "atmega808", "atmega809", "atmega1608", "atmega1609",
               "atmega3208", "atmega3209", "atmega4808", "atmega4809".

           "avrxmega4"
               "XMEGA" devices with more than 64 KiB and up to 128 KiB of
               program memory.  mcu = "atxmega64a3", "atxmega64a3u",
               "atxmega64a4u", "atxmega64b1", "atxmega64b3", "atxmega64c3",
               "atxmega64d3", "atxmega64d4".

           "avrxmega5"
               "XMEGA" devices with more than 64 KiB and up to 128 KiB of
               program memory and more than 64 KiB of RAM.  mcu = "atxmega64a1",
               "atxmega64a1u".

           "avrxmega6"
               "XMEGA" devices with more than 128 KiB of program memory.  mcu =
               "atxmega128a3", "atxmega128a3u", "atxmega128b1", "atxmega128b3",
               "atxmega128c3", "atxmega128d3", "atxmega128d4", "atxmega192a3",
               "atxmega192a3u", "atxmega192c3", "atxmega192d3", "atxmega256a3",
               "atxmega256a3b", "atxmega256a3bu", "atxmega256a3u",
               "atxmega256c3", "atxmega256d3", "atxmega384c3", "atxmega384d3".

           "avrxmega7"
               "XMEGA" devices with more than 128 KiB of program memory and more
               than 64 KiB of RAM.  mcu = "atxmega128a1", "atxmega128a1u",
               "atxmega128a4u".

           "avrtiny"
               "TINY" Tiny core devices with 512 B up to 4 KiB of program
               memory.  mcu = "attiny4", "attiny5", "attiny9", "attiny10",
               "attiny20", "attiny40".

           "avr1"
               This ISA is implemented by the minimal AVR core and supported for
               assembler only.  mcu = "attiny11", "attiny12", "attiny15",
               "attiny28", "at90s1200".

       -mabsdata
           Assume that all data in static storage can be accessed by LDS / STS
           instructions.  This option has only an effect on reduced Tiny devices
           like ATtiny40.  See also the "absdata" AVR Variable
           Attributes,variable attribute.

       -maccumulate-args
           Accumulate outgoing function arguments and acquire/release the needed
           stack space for outgoing function arguments once in function
           prologue/epilogue.  Without this option, outgoing arguments are
           pushed before calling a function and popped afterwards.

           Popping the arguments after the function call can be expensive on AVR
           so that accumulating the stack space might lead to smaller
           executables because arguments need not be removed from the stack
           after such a function call.

           This option can lead to reduced code size for functions that perform
           several calls to functions that get their arguments on the stack like
           calls to printf-like functions.

       -mbranch-cost=cost
           Set the branch costs for conditional branch instructions to cost.
           Reasonable values for cost are small, non-negative integers. The
           default branch cost is 0.

       -mcall-prologues
           Functions prologues/epilogues are expanded as calls to appropriate
           subroutines.  Code size is smaller.

       -mdouble=bits
       -mlong-double=bits
           Set the size (in bits) of the "double" or "long double" type,
           respectively.  Possible values for bits are 32 and 64.  Whether or
           not a specific value for bits is allowed depends on the
           "--with-double=" and "--with-long-double=" configure options
           ("https://gcc.gnu.org/install/configure.html#avr"), and the same
           applies for the default values of the options.

       -mgas-isr-prologues
           Interrupt service routines (ISRs) may use the "__gcc_isr" pseudo
           instruction supported by GNU Binutils.  If this option is on, the
           feature can still be disabled for individual ISRs by means of the AVR
           Function Attributes,,"no_gccisr" function attribute.  This feature is
           activated per default if optimization is on (but not with -Og,
           @pxref{Optimize Options}), and if GNU Binutils support PR21683
           ("https://sourceware.org/PR21683").

       -mint8
           Assume "int" to be 8-bit integer.  This affects the sizes of all
           types: a "char" is 1 byte, an "int" is 1 byte, a "long" is 2 bytes,
           and "long long" is 4 bytes.  Please note that this option does not
           conform to the C standards, but it results in smaller code size.

       -mmain-is-OS_task
           Do not save registers in "main".  The effect is the same like
           attaching attribute AVR Function Attributes,,"OS_task" to "main". It
           is activated per default if optimization is on.

       -mn-flash=num
           Assume that the flash memory has a size of num times 64 KiB.

       -mno-interrupts
           Generated code is not compatible with hardware interrupts.  Code size
           is smaller.

       -mrelax
           Try to replace "CALL" resp. "JMP" instruction by the shorter "RCALL"
           resp. "RJMP" instruction if applicable.  Setting -mrelax just adds
           the --mlink-relax option to the assembler's command line and the
           --relax option to the linker's command line.

           Jump relaxing is performed by the linker because jump offsets are not
           known before code is located. Therefore, the assembler code generated
           by the compiler is the same, but the instructions in the executable
           may differ from instructions in the assembler code.

           Relaxing must be turned on if linker stubs are needed, see the
           section on "EIND" and linker stubs below.

       -mrmw
           Assume that the device supports the Read-Modify-Write instructions
           "XCH", "LAC", "LAS" and "LAT".

       -mshort-calls
           Assume that "RJMP" and "RCALL" can target the whole program memory.

           This option is used internally for multilib selection.  It is not an
           optimization option, and you don't need to set it by hand.

       -msp8
           Treat the stack pointer register as an 8-bit register, i.e. assume
           the high byte of the stack pointer is zero.  In general, you don't
           need to set this option by hand.

           This option is used internally by the compiler to select and build
           multilibs for architectures "avr2" and "avr25".  These architectures
           mix devices with and without "SPH".  For any setting other than
           -mmcu=avr2 or -mmcu=avr25 the compiler driver adds or removes this
           option from the compiler proper's command line, because the compiler
           then knows if the device or architecture has an 8-bit stack pointer
           and thus no "SPH" register or not.

       -mstrict-X
           Use address register "X" in a way proposed by the hardware.  This
           means that "X" is only used in indirect, post-increment or pre-
           decrement addressing.

           Without this option, the "X" register may be used in the same way as
           "Y" or "Z" which then is emulated by additional instructions.  For
           example, loading a value with "X+const" addressing with a small non-
           negative "const < 64" to a register Rn is performed as

                   adiw r26, const   ; X += const
                   ld   <Rn>, X        ; <Rn> = *X
                   sbiw r26, const   ; X -= const

       -mtiny-stack
           Only change the lower 8 bits of the stack pointer.

       -mfract-convert-truncate
           Allow to use truncation instead of rounding towards zero for
           fractional fixed-point types.

       -nodevicelib
           Don't link against AVR-LibC's device specific library "lib<mcu>.a".

       -nodevicespecs
           Don't add -specs=device-specs/specs-mcu to the compiler driver's
           command line.  The user takes responsibility for supplying the sub-
           processes like compiler proper, assembler and linker with appropriate
           command line options.  This means that the user has to supply her
           private device specs file by means of -specs=path-to-specs-file.
           There is no more need for option -mmcu=mcu.

           This option can also serve as a replacement for the older way of
           specifying custom device-specs files that needed -B some-path to
           point to a directory which contains a folder named "device-specs"
           which contains a specs file named "specs-mcu", where mcu was
           specified by -mmcu=mcu.

       -Waddr-space-convert
           Warn about conversions between address spaces in the case where the
           resulting address space is not contained in the incoming address
           space.

       -Wmisspelled-isr
           Warn if the ISR is misspelled, i.e. without __vector prefix.  Enabled
           by default.

       "EIND" and Devices with More Than 128 Ki Bytes of Flash

       Pointers in the implementation are 16 bits wide.  The address of a
       function or label is represented as word address so that indirect jumps
       and calls can target any code address in the range of 64 Ki words.

       In order to facilitate indirect jump on devices with more than 128 Ki
       bytes of program memory space, there is a special function register
       called "EIND" that serves as most significant part of the target address
       when "EICALL" or "EIJMP" instructions are used.

       Indirect jumps and calls on these devices are handled as follows by the
       compiler and are subject to some limitations:

       *   The compiler never sets "EIND".

       *   The compiler uses "EIND" implicitly in "EICALL"/"EIJMP" instructions
           or might read "EIND" directly in order to emulate an indirect
           call/jump by means of a "RET" instruction.

       *   The compiler assumes that "EIND" never changes during the startup
           code or during the application. In particular, "EIND" is not
           saved/restored in function or interrupt service routine
           prologue/epilogue.

       *   For indirect calls to functions and computed goto, the linker
           generates stubs. Stubs are jump pads sometimes also called
           trampolines. Thus, the indirect call/jump jumps to such a stub.  The
           stub contains a direct jump to the desired address.

       *   Linker relaxation must be turned on so that the linker generates the
           stubs correctly in all situations. See the compiler option -mrelax
           and the linker option --relax.  There are corner cases where the
           linker is supposed to generate stubs but aborts without relaxation
           and without a helpful error message.

       *   The default linker script is arranged for code with "EIND = 0".  If
           code is supposed to work for a setup with "EIND != 0", a custom
           linker script has to be used in order to place the sections whose
           name start with ".trampolines" into the segment where "EIND" points
           to.

       *   The startup code from libgcc never sets "EIND".  Notice that startup
           code is a blend of code from libgcc and AVR-LibC.  For the impact of
           AVR-LibC on "EIND", see the AVR-LibC user manual
           ("http://nongnu.org/avr-libc/user-manual/").

       *   It is legitimate for user-specific startup code to set up "EIND"
           early, for example by means of initialization code located in section
           ".init3". Such code runs prior to general startup code that
           initializes RAM and calls constructors, but after the bit of startup
           code from AVR-LibC that sets "EIND" to the segment where the vector
           table is located.

                   #include <avr/io.h>

                   static void
                   __attribute__((section(".init3"),naked,used,no_instrument_function))
                   init3_set_eind (void)
                   {
                     __asm volatile ("ldi r24,pm_hh8(__trampolines_start)\n\t"
                                     "out %i0,r24" :: "n" (&EIND) : "r24","memory");
                   }

           The "__trampolines_start" symbol is defined in the linker script.

       *   Stubs are generated automatically by the linker if the following two
           conditions are met:

           -<The address of a label is taken by means of the "gs" modifier>
               (short for generate stubs) like so:

                       LDI r24, lo8(gs(<func>))
                       LDI r25, hi8(gs(<func>))

           -<The final location of that label is in a code segment>
               outside the segment where the stubs are located.

       *   The compiler emits such "gs" modifiers for code labels in the
           following situations:

           -<Taking address of a function or code label.>
           -<Computed goto.>
           -<If prologue-save function is used, see -mcall-prologues>
               command-line option.

           -<Switch/case dispatch tables. If you do not want such dispatch>
               tables you can specify the -fno-jump-tables command-line option.

           -<C and C++ constructors/destructors called during startup/shutdown.>
           -<If the tools hit a "gs()" modifier explained above.>
       *   Jumping to non-symbolic addresses like so is not supported:

                   int main (void)
                   {
                       /* Call function at word address 0x2 */
                       return ((int(*)(void)) 0x2)();
                   }

           Instead, a stub has to be set up, i.e. the function has to be called
           through a symbol ("func_4" in the example):

                   int main (void)
                   {
                       extern int func_4 (void);

                       /* Call function at byte address 0x4 */
                       return func_4();
                   }

           and the application be linked with -Wl,--defsym,func_4=0x4.
           Alternatively, "func_4" can be defined in the linker script.

       Handling of the "RAMPD", "RAMPX", "RAMPY" and "RAMPZ" Special Function
       Registers

       Some AVR devices support memories larger than the 64 KiB range that can
       be accessed with 16-bit pointers.  To access memory locations outside
       this 64 KiB range, the content of a "RAMP" register is used as high part
       of the address: The "X", "Y", "Z" address register is concatenated with
       the "RAMPX", "RAMPY", "RAMPZ" special function register, respectively, to
       get a wide address. Similarly, "RAMPD" is used together with direct
       addressing.

       *   The startup code initializes the "RAMP" special function registers
           with zero.

       *   If a AVR Named Address Spaces,named address space other than generic
           or "__flash" is used, then "RAMPZ" is set as needed before the
           operation.

       *   If the device supports RAM larger than 64 KiB and the compiler needs
           to change "RAMPZ" to accomplish an operation, "RAMPZ" is reset to
           zero after the operation.

       *   If the device comes with a specific "RAMP" register, the ISR
           prologue/epilogue saves/restores that SFR and initializes it with
           zero in case the ISR code might (implicitly) use it.

       *   RAM larger than 64 KiB is not supported by GCC for AVR targets.  If
           you use inline assembler to read from locations outside the 16-bit
           address range and change one of the "RAMP" registers, you must reset
           it to zero after the access.

       AVR Built-in Macros

       GCC defines several built-in macros so that the user code can test for
       the presence or absence of features.  Almost any of the following built-
       in macros are deduced from device capabilities and thus triggered by the
       -mmcu= command-line option.

       For even more AVR-specific built-in macros see AVR Named Address Spaces
       and AVR Built-in Functions.

       "__AVR_ARCH__"
           Build-in macro that resolves to a decimal number that identifies the
           architecture and depends on the -mmcu=mcu option.  Possible values
           are:

           2, 25, 3, 31, 35, 4, 5, 51, 6

           for mcu="avr2", "avr25", "avr3", "avr31", "avr35", "avr4", "avr5",
           "avr51", "avr6",

           respectively and

           100, 102, 103, 104, 105, 106, 107

           for mcu="avrtiny", "avrxmega2", "avrxmega3", "avrxmega4",
           "avrxmega5", "avrxmega6", "avrxmega7", respectively.  If mcu
           specifies a device, this built-in macro is set accordingly. For
           example, with -mmcu=atmega8 the macro is defined to 4.

       "__AVR_Device__"
           Setting -mmcu=device defines this built-in macro which reflects the
           device's name. For example, -mmcu=atmega8 defines the built-in macro
           "__AVR_ATmega8__", -mmcu=attiny261a defines "__AVR_ATtiny261A__",
           etc.

           The built-in macros' names follow the scheme "__AVR_Device__" where
           Device is the device name as from the AVR user manual. The difference
           between Device in the built-in macro and device in -mmcu=device is
           that the latter is always lowercase.

           If device is not a device but only a core architecture like avr51,
           this macro is not defined.

       "__AVR_DEVICE_NAME__"
           Setting -mmcu=device defines this built-in macro to the device's
           name. For example, with -mmcu=atmega8 the macro is defined to
           "atmega8".

           If device is not a device but only a core architecture like avr51,
           this macro is not defined.

       "__AVR_XMEGA__"
           The device / architecture belongs to the XMEGA family of devices.

       "__AVR_HAVE_ELPM__"
           The device has the "ELPM" instruction.

       "__AVR_HAVE_ELPMX__"
           The device has the "ELPM Rn,Z" and "ELPM Rn,Z+" instructions.

       "__AVR_HAVE_MOVW__"
           The device has the "MOVW" instruction to perform 16-bit register-
           register moves.

       "__AVR_HAVE_LPMX__"
           The device has the "LPM Rn,Z" and "LPM Rn,Z+" instructions.

       "__AVR_HAVE_MUL__"
           The device has a hardware multiplier.

       "__AVR_HAVE_JMP_CALL__"
           The device has the "JMP" and "CALL" instructions.  This is the case
           for devices with more than 8 KiB of program memory.

       "__AVR_HAVE_EIJMP_EICALL__"
       "__AVR_3_BYTE_PC__"
           The device has the "EIJMP" and "EICALL" instructions.  This is the
           case for devices with more than 128 KiB of program memory.  This also
           means that the program counter (PC) is 3 bytes wide.

       "__AVR_2_BYTE_PC__"
           The program counter (PC) is 2 bytes wide. This is the case for
           devices with up to 128 KiB of program memory.

       "__AVR_HAVE_8BIT_SP__"
       "__AVR_HAVE_16BIT_SP__"
           The stack pointer (SP) register is treated as 8-bit respectively
           16-bit register by the compiler.  The definition of these macros is
           affected by -mtiny-stack.

       "__AVR_HAVE_SPH__"
       "__AVR_SP8__"
           The device has the SPH (high part of stack pointer) special function
           register or has an 8-bit stack pointer, respectively.  The definition
           of these macros is affected by -mmcu= and in the cases of -mmcu=avr2
           and -mmcu=avr25 also by -msp8.

       "__AVR_HAVE_RAMPD__"
       "__AVR_HAVE_RAMPX__"
       "__AVR_HAVE_RAMPY__"
       "__AVR_HAVE_RAMPZ__"
           The device has the "RAMPD", "RAMPX", "RAMPY", "RAMPZ" special
           function register, respectively.

       "__NO_INTERRUPTS__"
           This macro reflects the -mno-interrupts command-line option.

       "__AVR_ERRATA_SKIP__"
       "__AVR_ERRATA_SKIP_JMP_CALL__"
           Some AVR devices (AT90S8515, ATmega103) must not skip 32-bit
           instructions because of a hardware erratum.  Skip instructions are
           "SBRS", "SBRC", "SBIS", "SBIC" and "CPSE".  The second macro is only
           defined if "__AVR_HAVE_JMP_CALL__" is also set.

       "__AVR_ISA_RMW__"
           The device has Read-Modify-Write instructions (XCH, LAC, LAS and
           LAT).

       "__AVR_SFR_OFFSET__=offset"
           Instructions that can address I/O special function registers directly
           like "IN", "OUT", "SBI", etc. may use a different address as if
           addressed by an instruction to access RAM like "LD" or "STS". This
           offset depends on the device architecture and has to be subtracted
           from the RAM address in order to get the respective I/O address.

       "__AVR_SHORT_CALLS__"
           The -mshort-calls command line option is set.

       "__AVR_PM_BASE_ADDRESS__=addr"
           Some devices support reading from flash memory by means of "LD*"
           instructions.  The flash memory is seen in the data address space at
           an offset of "__AVR_PM_BASE_ADDRESS__".  If this macro is not
           defined, this feature is not available.  If defined, the address
           space is linear and there is no need to put ".rodata" into RAM.  This
           is handled by the default linker description file, and is currently
           available for "avrtiny" and "avrxmega3".  Even more convenient, there
           is no need to use address spaces like "__flash" or features like
           attribute "progmem" and "pgm_read_*".

       "__WITH_AVRLIBC__"
           The compiler is configured to be used together with AVR-Libc.  See
           the --with-avrlibc configure option.

       "__HAVE_DOUBLE_MULTILIB__"
           Defined if -mdouble= acts as a multilib option.

       "__HAVE_DOUBLE32__"
       "__HAVE_DOUBLE64__"
           Defined if the compiler supports 32-bit double resp. 64-bit double.
           The actual layout is specified by option -mdouble=.

       "__DEFAULT_DOUBLE__"
           The size in bits of "double" if -mdouble= is not set.  To test the
           layout of "double" in a program, use the built-in macro
           "__SIZEOF_DOUBLE__".

       "__HAVE_LONG_DOUBLE32__"
       "__HAVE_LONG_DOUBLE64__"
       "__HAVE_LONG_DOUBLE_MULTILIB__"
       "__DEFAULT_LONG_DOUBLE__"
           Same as above, but for "long double" instead of "double".

       "__WITH_DOUBLE_COMPARISON__"
           Reflects the "--with-double-comparison={tristate|bool|libf7}"
           configure option ("https://gcc.gnu.org/install/configure.html#avr")
           and is defined to 2 or 3.

       "__WITH_LIBF7_LIBGCC__"
       "__WITH_LIBF7_MATH__"
       "__WITH_LIBF7_MATH_SYMBOLS__"
           Reflects the "--with-libf7={libgcc|math|math-symbols}"
           configure option ("https://gcc.gnu.org/install/configure.html#avr").

       Blackfin Options

       -mcpu=cpu[-sirevision]
           Specifies the name of the target Blackfin processor.  Currently, cpu
           can be one of bf512, bf514, bf516, bf518, bf522, bf523, bf524, bf525,
           bf526, bf527, bf531, bf532, bf533, bf534, bf536, bf537, bf538, bf539,
           bf542, bf544, bf547, bf548, bf549, bf542m, bf544m, bf547m, bf548m,
           bf549m, bf561, bf592.

           The optional sirevision specifies the silicon revision of the target
           Blackfin processor.  Any workarounds available for the targeted
           silicon revision are enabled.  If sirevision is none, no workarounds
           are enabled.  If sirevision is any, all workarounds for the targeted
           processor are enabled.  The "__SILICON_REVISION__" macro is defined
           to two hexadecimal digits representing the major and minor numbers in
           the silicon revision.  If sirevision is none, the
           "__SILICON_REVISION__" is not defined.  If sirevision is any, the
           "__SILICON_REVISION__" is defined to be 0xffff.  If this optional
           sirevision is not used, GCC assumes the latest known silicon revision
           of the targeted Blackfin processor.

           GCC defines a preprocessor macro for the specified cpu.  For the
           bfin-elf toolchain, this option causes the hardware BSP provided by
           libgloss to be linked in if -msim is not given.

           Without this option, bf532 is used as the processor by default.

           Note that support for bf561 is incomplete.  For bf561, only the
           preprocessor macro is defined.

       -msim
           Specifies that the program will be run on the simulator.  This causes
           the simulator BSP provided by libgloss to be linked in.  This option
           has effect only for bfin-elf toolchain.  Certain other options, such
           as -mid-shared-library and -mfdpic, imply -msim.

       -momit-leaf-frame-pointer
           Don't keep the frame pointer in a register for leaf functions.  This
           avoids the instructions to save, set up and restore frame pointers
           and makes an extra register available in leaf functions.

       -mspecld-anomaly
           When enabled, the compiler ensures that the generated code does not
           contain speculative loads after jump instructions. If this option is
           used, "__WORKAROUND_SPECULATIVE_LOADS" is defined.

       -mno-specld-anomaly
           Don't generate extra code to prevent speculative loads from
           occurring.

       -mcsync-anomaly
           When enabled, the compiler ensures that the generated code does not
           contain CSYNC or SSYNC instructions too soon after conditional
           branches.  If this option is used, "__WORKAROUND_SPECULATIVE_SYNCS"
           is defined.

       -mno-csync-anomaly
           Don't generate extra code to prevent CSYNC or SSYNC instructions from
           occurring too soon after a conditional branch.

       -mlow64k
           When enabled, the compiler is free to take advantage of the knowledge
           that the entire program fits into the low 64k of memory.

       -mno-low64k
           Assume that the program is arbitrarily large.  This is the default.

       -mstack-check-l1
           Do stack checking using information placed into L1 scratchpad memory
           by the uClinux kernel.

       -mid-shared-library
           Generate code that supports shared libraries via the library ID
           method.  This allows for execute in place and shared libraries in an
           environment without virtual memory management.  This option implies
           -fPIC.  With a bfin-elf target, this option implies -msim.

       -mno-id-shared-library
           Generate code that doesn't assume ID-based shared libraries are being
           used.  This is the default.

       -mleaf-id-shared-library
           Generate code that supports shared libraries via the library ID
           method, but assumes that this library or executable won't link
           against any other ID shared libraries.  That allows the compiler to
           use faster code for jumps and calls.

       -mno-leaf-id-shared-library
           Do not assume that the code being compiled won't link against any ID
           shared libraries.  Slower code is generated for jump and call insns.

       -mshared-library-id=n
           Specifies the identification number of the ID-based shared library
           being compiled.  Specifying a value of 0 generates more compact code;
           specifying other values forces the allocation of that number to the
           current library but is no more space- or time-efficient than omitting
           this option.

       -msep-data
           Generate code that allows the data segment to be located in a
           different area of memory from the text segment.  This allows for
           execute in place in an environment without virtual memory management
           by eliminating relocations against the text section.

       -mno-sep-data
           Generate code that assumes that the data segment follows the text
           segment.  This is the default.

       -mlong-calls
       -mno-long-calls
           Tells the compiler to perform function calls by first loading the
           address of the function into a register and then performing a
           subroutine call on this register.  This switch is needed if the
           target function lies outside of the 24-bit addressing range of the
           offset-based version of subroutine call instruction.

           This feature is not enabled by default.  Specifying -mno-long-calls
           restores the default behavior.  Note these switches have no effect on
           how the compiler generates code to handle function calls via function
           pointers.

       -mfast-fp
           Link with the fast floating-point library. This library relaxes some
           of the IEEE floating-point standard's rules for checking inputs
           against Not-a-Number (NAN), in the interest of performance.

       -minline-plt
           Enable inlining of PLT entries in function calls to functions that
           are not known to bind locally.  It has no effect without -mfdpic.

       -mmulticore
           Build a standalone application for multicore Blackfin processors.
           This option causes proper start files and link scripts supporting
           multicore to be used, and defines the macro "__BFIN_MULTICORE".  It
           can only be used with -mcpu=bf561[-sirevision].

           This option can be used with -mcorea or -mcoreb, which selects the
           one-application-per-core programming model.  Without -mcorea or
           -mcoreb, the single-application/dual-core programming model is used.
           In this model, the main function of Core B should be named as
           "coreb_main".

           If this option is not used, the single-core application programming
           model is used.

       -mcorea
           Build a standalone application for Core A of BF561 when using the
           one-application-per-core programming model. Proper start files and
           link scripts are used to support Core A, and the macro "__BFIN_COREA"
           is defined.  This option can only be used in conjunction with
           -mmulticore.

       -mcoreb
           Build a standalone application for Core B of BF561 when using the
           one-application-per-core programming model. Proper start files and
           link scripts are used to support Core B, and the macro "__BFIN_COREB"
           is defined. When this option is used, "coreb_main" should be used
           instead of "main".  This option can only be used in conjunction with
           -mmulticore.

       -msdram
           Build a standalone application for SDRAM. Proper start files and link
           scripts are used to put the application into SDRAM, and the macro
           "__BFIN_SDRAM" is defined.  The loader should initialize SDRAM before
           loading the application.

       -micplb
           Assume that ICPLBs are enabled at run time.  This has an effect on
           certain anomaly workarounds.  For Linux targets, the default is to
           assume ICPLBs are enabled; for standalone applications the default is
           off.

       C6X Options

       -march=name
           This specifies the name of the target architecture.  GCC uses this
           name to determine what kind of instructions it can emit when
           generating assembly code.  Permissible names are: c62x, c64x, c64x+,
           c67x, c67x+, c674x.

       -mbig-endian
           Generate code for a big-endian target.

       -mlittle-endian
           Generate code for a little-endian target.  This is the default.

       -msim
           Choose startup files and linker script suitable for the simulator.

       -msdata=default
           Put small global and static data in the ".neardata" section, which is
           pointed to by register "B14".  Put small uninitialized global and
           static data in the ".bss" section, which is adjacent to the
           ".neardata" section.  Put small read-only data into the ".rodata"
           section.  The corresponding sections used for large pieces of data
           are ".fardata", ".far" and ".const".

       -msdata=all
           Put all data, not just small objects, into the sections reserved for
           small data, and use addressing relative to the "B14" register to
           access them.

       -msdata=none
           Make no use of the sections reserved for small data, and use absolute
           addresses to access all data.  Put all initialized global and static
           data in the ".fardata" section, and all uninitialized data in the
           ".far" section.  Put all constant data into the ".const" section.

       CRIS Options

       These options are defined specifically for the CRIS ports.

       -march=architecture-type
       -mcpu=architecture-type
           Generate code for the specified architecture.  The choices for
           architecture-type are v3, v8 and v10 for respectively ETRAX 4,
           ETRAX 100, and ETRAX 100 LX.  Default is v0 except for cris-axis-
           linux-gnu, where the default is v10.

       -mtune=architecture-type
           Tune to architecture-type everything applicable about the generated
           code, except for the ABI and the set of available instructions.  The
           choices for architecture-type are the same as for
           -march=architecture-type.

       -mmax-stack-frame=n
           Warn when the stack frame of a function exceeds n bytes.

       -metrax4
       -metrax100
           The options -metrax4 and -metrax100 are synonyms for -march=v3 and
           -march=v8 respectively.

       -mmul-bug-workaround
       -mno-mul-bug-workaround
           Work around a bug in the "muls" and "mulu" instructions for CPU
           models where it applies.  This option is active by default.

       -mpdebug
           Enable CRIS-specific verbose debug-related information in the
           assembly code.  This option also has the effect of turning off the
           #NO_APP formatted-code indicator to the assembler at the beginning of
           the assembly file.

       -mcc-init
           Do not use condition-code results from previous instruction; always
           emit compare and test instructions before use of condition codes.

       -mno-side-effects
           Do not emit instructions with side effects in addressing modes other
           than post-increment.

       -mstack-align
       -mno-stack-align
       -mdata-align
       -mno-data-align
       -mconst-align
       -mno-const-align
           These options (no- options) arrange (eliminate arrangements) for the
           stack frame, individual data and constants to be aligned for the
           maximum single data access size for the chosen CPU model.  The
           default is to arrange for 32-bit alignment.  ABI details such as
           structure layout are not affected by these options.

       -m32-bit
       -m16-bit
       -m8-bit
           Similar to the stack- data- and const-align options above, these
           options arrange for stack frame, writable data and constants to all
           be 32-bit, 16-bit or 8-bit aligned.  The default is 32-bit alignment.

       -mno-prologue-epilogue
       -mprologue-epilogue
           With -mno-prologue-epilogue, the normal function prologue and
           epilogue which set up the stack frame are omitted and no return
           instructions or return sequences are generated in the code.  Use this
           option only together with visual inspection of the compiled code: no
           warnings or errors are generated when call-saved registers must be
           saved, or storage for local variables needs to be allocated.

       -mno-gotplt
       -mgotplt
           With -fpic and -fPIC, don't generate (do generate) instruction
           sequences that load addresses for functions from the PLT part of the
           GOT rather than (traditional on other architectures) calls to the
           PLT.  The default is -mgotplt.

       -melf
           Legacy no-op option only recognized with the cris-axis-elf and cris-
           axis-linux-gnu targets.

       -mlinux
           Legacy no-op option only recognized with the cris-axis-linux-gnu
           target.

       -sim
           This option, recognized for the cris-axis-elf, arranges to link with
           input-output functions from a simulator library.  Code, initialized
           data and zero-initialized data are allocated consecutively.

       -sim2
           Like -sim, but pass linker options to locate initialized data at
           0x40000000 and zero-initialized data at 0x80000000.

       CR16 Options

       These options are defined specifically for the CR16 ports.

       -mmac
           Enable the use of multiply-accumulate instructions. Disabled by
           default.

       -mcr16cplus
       -mcr16c
           Generate code for CR16C or CR16C+ architecture. CR16C+ architecture
           is default.

       -msim
           Links the library libsim.a which is in compatible with simulator.
           Applicable to ELF compiler only.

       -mint32
           Choose integer type as 32-bit wide.

       -mbit-ops
           Generates "sbit"/"cbit" instructions for bit manipulations.

       -mdata-model=model
           Choose a data model. The choices for model are near, far or medium.
           medium is default.  However, far is not valid with -mcr16c, as the
           CR16C architecture does not support the far data model.

       C-SKY Options

       GCC supports these options when compiling for C-SKY V2 processors.

       -march=arch
           Specify the C-SKY target architecture.  Valid values for arch are:
           ck801, ck802, ck803, ck807, and ck810.  The default is ck810.

       -mcpu=cpu
           Specify the C-SKY target processor.  Valid values for cpu are: ck801,
           ck801t, ck802, ck802t, ck802j, ck803, ck803h, ck803t, ck803ht,
           ck803f, ck803fh, ck803e, ck803eh, ck803et, ck803eht, ck803ef,
           ck803efh, ck803ft, ck803eft, ck803efht, ck803r1, ck803hr1, ck803tr1,
           ck803htr1, ck803fr1, ck803fhr1, ck803er1, ck803ehr1, ck803etr1,
           ck803ehtr1, ck803efr1, ck803efhr1, ck803ftr1, ck803eftr1,
           ck803efhtr1, ck803s, ck803st, ck803se, ck803sf, ck803sef, ck803seft,
           ck807e, ck807ef, ck807, ck807f, ck810e, ck810et, ck810ef, ck810eft,
           ck810, ck810v, ck810f, ck810t, ck810fv, ck810tv, ck810ft, and
           ck810ftv.

       -mbig-endian
       -EB
       -mlittle-endian
       -EL Select big- or little-endian code.  The default is little-endian.

       -mfloat-abi=name
           Specifies which floating-point ABI to use.  Permissible values are:
           soft, softfp and hard.

           Specifying soft causes GCC to generate output containing library
           calls for floating-point operations.  softfp allows the generation of
           code using hardware floating-point instructions, but still uses the
           soft-float calling conventions.  hard allows generation of floating-
           point instructions and uses FPU-specific calling conventions.

           The default depends on the specific target configuration.  Note that
           the hard-float and soft-float ABIs are not link-compatible; you must
           compile your entire program with the same ABI, and link with a
           compatible set of libraries.

       -mhard-float
       -msoft-float
           Select hardware or software floating-point implementations.  The
           default is soft float.

       -mdouble-float
       -mno-double-float
           When -mhard-float is in effect, enable generation of double-precision
           float instructions.  This is the default except when compiling for
           CK803.

       -mfdivdu
       -mno-fdivdu
           When -mhard-float is in effect, enable generation of "frecipd",
           "fsqrtd", and "fdivd" instructions.  This is the default except when
           compiling for CK803.

       -mfpu=fpu
           Select the floating-point processor.  This option can only be used
           with -mhard-float.  Values for fpu are fpv2_sf (equivalent to
           -mno-double-float -mno-fdivdu), fpv2 (-mdouble-float -mno-divdu), and
           fpv2_divd (-mdouble-float -mdivdu).

       -melrw
       -mno-elrw
           Enable the extended "lrw" instruction.  This option defaults to on
           for CK801 and off otherwise.

       -mistack
       -mno-istack
           Enable interrupt stack instructions; the default is off.

           The -mistack option is required to handle the "interrupt" and "isr"
           function attributes.

       -mmp
           Enable multiprocessor instructions; the default is off.

       -mcp
           Enable coprocessor instructions; the default is off.

       -mcache
           Enable coprocessor instructions; the default is off.

       -msecurity
           Enable C-SKY security instructions; the default is off.

       -mtrust
           Enable C-SKY trust instructions; the default is off.

       -mdsp
       -medsp
       -mvdsp
           Enable C-SKY DSP, Enhanced DSP, or Vector DSP instructions,
           respectively.  All of these options default to off.

       -mdiv
       -mno-div
           Generate divide instructions.  Default is off.

       -msmart
       -mno-smart
           Generate code for Smart Mode, using only registers numbered 0-7 to
           allow use of 16-bit instructions.  This option is ignored for CK801
           where this is the required behavior, and it defaults to on for CK802.
           For other targets, the default is off.

       -mhigh-registers
       -mno-high-registers
           Generate code using the high registers numbered 16-31.  This option
           is not supported on CK801, CK802, or CK803, and is enabled by default
           for other processors.

       -manchor
       -mno-anchor
           Generate code using global anchor symbol addresses.

       -mpushpop
       -mno-pushpop
           Generate code using "push" and "pop" instructions.  This option
           defaults to on.

       -mmultiple-stld
       -mstm
       -mno-multiple-stld
       -mno-stm
           Generate code using "stm" and "ldm" instructions.  This option isn't
           supported on CK801 but is enabled by default on other processors.

       -mconstpool
       -mno-constpool
           Create constant pools in the compiler instead of deferring it to the
           assembler.  This option is the default and required for correct code
           generation on CK801 and CK802, and is optional on other processors.

       -mstack-size
       -mno-stack-size
           Emit ".stack_size" directives for each function in the assembly
           output.  This option defaults to off.

       -mccrt
       -mno-ccrt
           Generate code for the C-SKY compiler runtime instead of libgcc.  This
           option defaults to off.

       -mbranch-cost=n
           Set the branch costs to roughly "n" instructions.  The default is 1.

       -msched-prolog
       -mno-sched-prolog
           Permit scheduling of function prologue and epilogue sequences.  Using
           this option can result in code that is not compliant with the C-SKY
           V2 ABI prologue requirements and that cannot be debugged or
           backtraced.  It is disabled by default.

       -msim
           Links the library libsemi.a which is in compatible with simulator.
           Applicable to ELF compiler only.

       Darwin Options

       These options are defined for all architectures running the Darwin
       operating system.

       FSF GCC on Darwin does not create "fat" object files; it creates an
       object file for the single architecture that GCC was built to target.
       Apple's GCC on Darwin does create "fat" files if multiple -arch options
       are used; it does so by running the compiler or linker multiple times and
       joining the results together with lipo.

       The subtype of the file created (like ppc7400 or ppc970 or i686) is
       determined by the flags that specify the ISA that GCC is targeting, like
       -mcpu or -march.  The -force_cpusubtype_ALL option can be used to
       override this.

       The Darwin tools vary in their behavior when presented with an ISA
       mismatch.  The assembler, as, only permits instructions to be used that
       are valid for the subtype of the file it is generating, so you cannot put
       64-bit instructions in a ppc750 object file.  The linker for shared
       libraries, /usr/bin/libtool, fails and prints an error if asked to create
       a shared library with a less restrictive subtype than its input files
       (for instance, trying to put a ppc970 object file in a ppc7400 library).
       The linker for executables, ld, quietly gives the executable the most
       restrictive subtype of any of its input files.

       -Fdir
           Add the framework directory dir to the head of the list of
           directories to be searched for header files.  These directories are
           interleaved with those specified by -I options and are scanned in a
           left-to-right order.

           A framework directory is a directory with frameworks in it.  A
           framework is a directory with a Headers and/or PrivateHeaders
           directory contained directly in it that ends in .framework.  The name
           of a framework is the name of this directory excluding the
           .framework.  Headers associated with the framework are found in one
           of those two directories, with Headers being searched first.  A
           subframework is a framework directory that is in a framework's
           Frameworks directory.  Includes of subframework headers can only
           appear in a header of a framework that contains the subframework, or
           in a sibling subframework header.  Two subframeworks are siblings if
           they occur in the same framework.  A subframework should not have the
           same name as a framework; a warning is issued if this is violated.
           Currently a subframework cannot have subframeworks; in the future,
           the mechanism may be extended to support this.  The standard
           frameworks can be found in /System/Library/Frameworks and
           /Library/Frameworks.  An example include looks like "#include
           <Framework/header.h>", where Framework denotes the name of the
           framework and header.h is found in the PrivateHeaders or Headers
           directory.

       -iframeworkdir
           Like -F except the directory is a treated as a system directory.  The
           main difference between this -iframework and -F is that with
           -iframework the compiler does not warn about constructs contained
           within header files found via dir.  This option is valid only for the
           C family of languages.

       -gused
           Emit debugging information for symbols that are used.  For stabs
           debugging format, this enables -feliminate-unused-debug-symbols.
           This is by default ON.

       -gfull
           Emit debugging information for all symbols and types.

       -mmacosx-version-min=version
           The earliest version of MacOS X that this executable will run on is
           version.  Typical values of version include 10.1, 10.2, and 10.3.9.

           If the compiler was built to use the system's headers by default,
           then the default for this option is the system version on which the
           compiler is running, otherwise the default is to make choices that
           are compatible with as many systems and code bases as possible.

       -mkernel
           Enable kernel development mode.  The -mkernel option sets -static,
           -fno-common, -fno-use-cxa-atexit, -fno-exceptions,
           -fno-non-call-exceptions, -fapple-kext, -fno-weak and -fno-rtti where
           applicable.  This mode also sets -mno-altivec, -msoft-float,
           -fno-builtin and -mlong-branch for PowerPC targets.

       -mone-byte-bool
           Override the defaults for "bool" so that "sizeof(bool)==1".  By
           default "sizeof(bool)" is 4 when compiling for Darwin/PowerPC and 1
           when compiling for Darwin/x86, so this option has no effect on x86.

           Warning: The -mone-byte-bool switch causes GCC to generate code that
           is not binary compatible with code generated without that switch.
           Using this switch may require recompiling all other modules in a
           program, including system libraries.  Use this switch to conform to a
           non-default data model.

       -mfix-and-continue
       -ffix-and-continue
       -findirect-data
           Generate code suitable for fast turnaround development, such as to
           allow GDB to dynamically load .o files into already-running programs.
           -findirect-data and -ffix-and-continue are provided for backwards
           compatibility.

       -all_load
           Loads all members of static archive libraries.  See man ld(1) for
           more information.

       -arch_errors_fatal
           Cause the errors having to do with files that have the wrong
           architecture to be fatal.

       -bind_at_load
           Causes the output file to be marked such that the dynamic linker will
           bind all undefined references when the file is loaded or launched.

       -bundle
           Produce a Mach-o bundle format file.  See man ld(1) for more
           information.

       -bundle_loader executable
           This option specifies the executable that will load the build output
           file being linked.  See man ld(1) for more information.

       -dynamiclib
           When passed this option, GCC produces a dynamic library instead of an
           executable when linking, using the Darwin libtool command.

       -force_cpusubtype_ALL
           This causes GCC's output file to have the ALL subtype, instead of one
           controlled by the -mcpu or -march option.

       -allowable_client  client_name
       -client_name
       -compatibility_version
       -current_version
       -dead_strip
       -dependency-file
       -dylib_file
       -dylinker_install_name
       -dynamic
       -exported_symbols_list
       -filelist
       -flat_namespace
       -force_flat_namespace
       -headerpad_max_install_names
       -image_base
       -init
       -install_name
       -keep_private_externs
       -multi_module
       -multiply_defined
       -multiply_defined_unused
       -noall_load
       -no_dead_strip_inits_and_terms
       -nofixprebinding
       -nomultidefs
       -noprebind
       -noseglinkedit
       -pagezero_size
       -prebind
       -prebind_all_twolevel_modules
       -private_bundle
       -read_only_relocs
       -sectalign
       -sectobjectsymbols
       -whyload
       -seg1addr
       -sectcreate
       -sectobjectsymbols
       -sectorder
       -segaddr
       -segs_read_only_addr
       -segs_read_write_addr
       -seg_addr_table
       -seg_addr_table_filename
       -seglinkedit
       -segprot
       -segs_read_only_addr
       -segs_read_write_addr
       -single_module
       -static
       -sub_library
       -sub_umbrella
       -twolevel_namespace
       -umbrella
       -undefined
       -unexported_symbols_list
       -weak_reference_mismatches
       -whatsloaded
           These options are passed to the Darwin linker.  The Darwin linker man
           page describes them in detail.

       DEC Alpha Options

       These -m options are defined for the DEC Alpha implementations:

       -mno-soft-float
       -msoft-float
           Use (do not use) the hardware floating-point instructions for
           floating-point operations.  When -msoft-float is specified, functions
           in libgcc.a are used to perform floating-point operations.  Unless
           they are replaced by routines that emulate the floating-point
           operations, or compiled in such a way as to call such emulations
           routines, these routines issue floating-point operations.   If you
           are compiling for an Alpha without floating-point operations, you
           must ensure that the library is built so as not to call them.

           Note that Alpha implementations without floating-point operations are
           required to have floating-point registers.

       -mfp-reg
       -mno-fp-regs
           Generate code that uses (does not use) the floating-point register
           set.  -mno-fp-regs implies -msoft-float.  If the floating-point
           register set is not used, floating-point operands are passed in
           integer registers as if they were integers and floating-point results
           are passed in $0 instead of $f0.  This is a non-standard calling
           sequence, so any function with a floating-point argument or return
           value called by code compiled with -mno-fp-regs must also be compiled
           with that option.

           A typical use of this option is building a kernel that does not use,
           and hence need not save and restore, any floating-point registers.

       -mieee
           The Alpha architecture implements floating-point hardware optimized
           for maximum performance.  It is mostly compliant with the IEEE
           floating-point standard.  However, for full compliance, software
           assistance is required.  This option generates code fully IEEE-
           compliant code except that the inexact-flag is not maintained (see
           below).  If this option is turned on, the preprocessor macro
           "_IEEE_FP" is defined during compilation.  The resulting code is less
           efficient but is able to correctly support denormalized numbers and
           exceptional IEEE values such as not-a-number and plus/minus infinity.
           Other Alpha compilers call this option -ieee_with_no_inexact.

       -mieee-with-inexact
           This is like -mieee except the generated code also maintains the IEEE
           inexact-flag.  Turning on this option causes the generated code to
           implement fully-compliant IEEE math.  In addition to "_IEEE_FP",
           "_IEEE_FP_EXACT" is defined as a preprocessor macro.  On some Alpha
           implementations the resulting code may execute significantly slower
           than the code generated by default.  Since there is very little code
           that depends on the inexact-flag, you should normally not specify
           this option.  Other Alpha compilers call this option
           -ieee_with_inexact.

       -mfp-trap-mode=trap-mode
           This option controls what floating-point related traps are enabled.
           Other Alpha compilers call this option -fptm trap-mode.  The trap
           mode can be set to one of four values:

           n   This is the default (normal) setting.  The only traps that are
               enabled are the ones that cannot be disabled in software (e.g.,
               division by zero trap).

           u   In addition to the traps enabled by n, underflow traps are
               enabled as well.

           su  Like u, but the instructions are marked to be safe for software
               completion (see Alpha architecture manual for details).

           sui Like su, but inexact traps are enabled as well.

       -mfp-rounding-mode=rounding-mode
           Selects the IEEE rounding mode.  Other Alpha compilers call this
           option -fprm rounding-mode.  The rounding-mode can be one of:

           n   Normal IEEE rounding mode.  Floating-point numbers are rounded
               towards the nearest machine number or towards the even machine
               number in case of a tie.

           m   Round towards minus infinity.

           c   Chopped rounding mode.  Floating-point numbers are rounded
               towards zero.

           d   Dynamic rounding mode.  A field in the floating-point control
               register (fpcr, see Alpha architecture reference manual) controls
               the rounding mode in effect.  The C library initializes this
               register for rounding towards plus infinity.  Thus, unless your
               program modifies the fpcr, d corresponds to round towards plus
               infinity.

       -mtrap-precision=trap-precision
           In the Alpha architecture, floating-point traps are imprecise.  This
           means without software assistance it is impossible to recover from a
           floating trap and program execution normally needs to be terminated.
           GCC can generate code that can assist operating system trap handlers
           in determining the exact location that caused a floating-point trap.
           Depending on the requirements of an application, different levels of
           precisions can be selected:

           p   Program precision.  This option is the default and means a trap
               handler can only identify which program caused a floating-point
               exception.

           f   Function precision.  The trap handler can determine the function
               that caused a floating-point exception.

           i   Instruction precision.  The trap handler can determine the exact
               instruction that caused a floating-point exception.

           Other Alpha compilers provide the equivalent options called
           -scope_safe and -resumption_safe.

       -mieee-conformant
           This option marks the generated code as IEEE conformant.  You must
           not use this option unless you also specify -mtrap-precision=i and
           either -mfp-trap-mode=su or -mfp-trap-mode=sui.  Its only effect is
           to emit the line .eflag 48 in the function prologue of the generated
           assembly file.

       -mbuild-constants
           Normally GCC examines a 32- or 64-bit integer constant to see if it
           can construct it from smaller constants in two or three instructions.
           If it cannot, it outputs the constant as a literal and generates code
           to load it from the data segment at run time.

           Use this option to require GCC to construct all integer constants
           using code, even if it takes more instructions (the maximum is six).

           You typically use this option to build a shared library dynamic
           loader.  Itself a shared library, it must relocate itself in memory
           before it can find the variables and constants in its own data
           segment.

       -mbwx
       -mno-bwx
       -mcix
       -mno-cix
       -mfix
       -mno-fix
       -mmax
       -mno-max
           Indicate whether GCC should generate code to use the optional BWX,
           CIX, FIX and MAX instruction sets.  The default is to use the
           instruction sets supported by the CPU type specified via -mcpu=
           option or that of the CPU on which GCC was built if none is
           specified.

       -mfloat-vax
       -mfloat-ieee
           Generate code that uses (does not use) VAX F and G floating-point
           arithmetic instead of IEEE single and double precision.

       -mexplicit-relocs
       -mno-explicit-relocs
           Older Alpha assemblers provided no way to generate symbol relocations
           except via assembler macros.  Use of these macros does not allow
           optimal instruction scheduling.  GNU binutils as of version 2.12
           supports a new syntax that allows the compiler to explicitly mark
           which relocations should apply to which instructions.  This option is
           mostly useful for debugging, as GCC detects the capabilities of the
           assembler when it is built and sets the default accordingly.

       -msmall-data
       -mlarge-data
           When -mexplicit-relocs is in effect, static data is accessed via gp-
           relative relocations.  When -msmall-data is used, objects 8 bytes
           long or smaller are placed in a small data area (the ".sdata" and
           ".sbss" sections) and are accessed via 16-bit relocations off of the
           $gp register.  This limits the size of the small data area to 64KB,
           but allows the variables to be directly accessed via a single
           instruction.

           The default is -mlarge-data.  With this option the data area is
           limited to just below 2GB.  Programs that require more than 2GB of
           data must use "malloc" or "mmap" to allocate the data in the heap
           instead of in the program's data segment.

           When generating code for shared libraries, -fpic implies -msmall-data
           and -fPIC implies -mlarge-data.

       -msmall-text
       -mlarge-text
           When -msmall-text is used, the compiler assumes that the code of the
           entire program (or shared library) fits in 4MB, and is thus reachable
           with a branch instruction.  When -msmall-data is used, the compiler
           can assume that all local symbols share the same $gp value, and thus
           reduce the number of instructions required for a function call from 4
           to 1.

           The default is -mlarge-text.

       -mcpu=cpu_type
           Set the instruction set and instruction scheduling parameters for
           machine type cpu_type.  You can specify either the EV style name or
           the corresponding chip number.  GCC supports scheduling parameters
           for the EV4, EV5 and EV6 family of processors and chooses the default
           values for the instruction set from the processor you specify.  If
           you do not specify a processor type, GCC defaults to the processor on
           which the compiler was built.

           Supported values for cpu_type are

           ev4
           ev45
           21064
               Schedules as an EV4 and has no instruction set extensions.

           ev5
           21164
               Schedules as an EV5 and has no instruction set extensions.

           ev56
           21164a
               Schedules as an EV5 and supports the BWX extension.

           pca56
           21164pc
           21164PC
               Schedules as an EV5 and supports the BWX and MAX extensions.

           ev6
           21264
               Schedules as an EV6 and supports the BWX, FIX, and MAX
               extensions.

           ev67
           21264a
               Schedules as an EV6 and supports the BWX, CIX, FIX, and MAX
               extensions.

           Native toolchains also support the value native, which selects the
           best architecture option for the host processor.  -mcpu=native has no
           effect if GCC does not recognize the processor.

       -mtune=cpu_type
           Set only the instruction scheduling parameters for machine type
           cpu_type.  The instruction set is not changed.

           Native toolchains also support the value native, which selects the
           best architecture option for the host processor.  -mtune=native has
           no effect if GCC does not recognize the processor.

       -mmemory-latency=time
           Sets the latency the scheduler should assume for typical memory
           references as seen by the application.  This number is highly
           dependent on the memory access patterns used by the application and
           the size of the external cache on the machine.

           Valid options for time are

           number
               A decimal number representing clock cycles.

           L1
           L2
           L3
           main
               The compiler contains estimates of the number of clock cycles for
               "typical" EV4 & EV5 hardware for the Level 1, 2 & 3 caches (also
               called Dcache, Scache, and Bcache), as well as to main memory.
               Note that L3 is only valid for EV5.

       eBPF Options

       -mframe-limit=bytes
           This specifies the hard limit for frame sizes, in bytes.  Currently,
           the value that can be specified should be less than or equal to
           32767.  Defaults to whatever limit is imposed by the version of the
           Linux kernel targeted.

       -mkernel=version
           This specifies the minimum version of the kernel that will run the
           compiled program.  GCC uses this version to determine which
           instructions to use, what kernel helpers to allow, etc.  Currently,
           version can be one of 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8,
           4.9, 4.10, 4.11, 4.12, 4.13, 4.14, 4.15, 4.16, 4.17, 4.18, 4.19,
           4.20, 5.0, 5.1, 5.2, latest and native.

       -mbig-endian
           Generate code for a big-endian target.

       -mlittle-endian
           Generate code for a little-endian target.  This is the default.

       -mxbpf
           Generate code for an expanded version of BPF, which relaxes some of
           the restrictions imposed by the BPF architecture:

           -<Save and restore callee-saved registers at function entry and>
               exit, respectively.

       FR30 Options

       These options are defined specifically for the FR30 port.

       -msmall-model
           Use the small address space model.  This can produce smaller code,
           but it does assume that all symbolic values and addresses fit into a
           20-bit range.

       -mno-lsim
           Assume that runtime support has been provided and so there is no need
           to include the simulator library (libsim.a) on the linker command
           line.

       FT32 Options

       These options are defined specifically for the FT32 port.

       -msim
           Specifies that the program will be run on the simulator.  This causes
           an alternate runtime startup and library to be linked.  You must not
           use this option when generating programs that will run on real
           hardware; you must provide your own runtime library for whatever I/O
           functions are needed.

       -mlra
           Enable Local Register Allocation.  This is still experimental for
           FT32, so by default the compiler uses standard reload.

       -mnodiv
           Do not use div and mod instructions.

       -mft32b
           Enable use of the extended instructions of the FT32B processor.

       -mcompress
           Compress all code using the Ft32B code compression scheme.

       -mnopm
           Do not generate code that reads program memory.

       FRV Options

       -mgpr-32
           Only use the first 32 general-purpose registers.

       -mgpr-64
           Use all 64 general-purpose registers.

       -mfpr-32
           Use only the first 32 floating-point registers.

       -mfpr-64
           Use all 64 floating-point registers.

       -mhard-float
           Use hardware instructions for floating-point operations.

       -msoft-float
           Use library routines for floating-point operations.

       -malloc-cc
           Dynamically allocate condition code registers.

       -mfixed-cc
           Do not try to dynamically allocate condition code registers, only use
           "icc0" and "fcc0".

       -mdword
           Change ABI to use double word insns.

       -mno-dword
           Do not use double word instructions.

       -mdouble
           Use floating-point double instructions.

       -mno-double
           Do not use floating-point double instructions.

       -mmedia
           Use media instructions.

       -mno-media
           Do not use media instructions.

       -mmuladd
           Use multiply and add/subtract instructions.

       -mno-muladd
           Do not use multiply and add/subtract instructions.

       -mfdpic
           Select the FDPIC ABI, which uses function descriptors to represent
           pointers to functions.  Without any PIC/PIE-related options, it
           implies -fPIE.  With -fpic or -fpie, it assumes GOT entries and small
           data are within a 12-bit range from the GOT base address; with -fPIC
           or -fPIE, GOT offsets are computed with 32 bits.  With a bfin-elf
           target, this option implies -msim.

       -minline-plt
           Enable inlining of PLT entries in function calls to functions that
           are not known to bind locally.  It has no effect without -mfdpic.
           It's enabled by default if optimizing for speed and compiling for
           shared libraries (i.e., -fPIC or -fpic), or when an optimization
           option such as -O3 or above is present in the command line.

       -mTLS
           Assume a large TLS segment when generating thread-local code.

       -mtls
           Do not assume a large TLS segment when generating thread-local code.

       -mgprel-ro
           Enable the use of "GPREL" relocations in the FDPIC ABI for data that
           is known to be in read-only sections.  It's enabled by default,
           except for -fpic or -fpie: even though it may help make the global
           offset table smaller, it trades 1 instruction for 4.  With -fPIC or
           -fPIE, it trades 3 instructions for 4, one of which may be shared by
           multiple symbols, and it avoids the need for a GOT entry for the
           referenced symbol, so it's more likely to be a win.  If it is not,
           -mno-gprel-ro can be used to disable it.

       -multilib-library-pic
           Link with the (library, not FD) pic libraries.  It's implied by
           -mlibrary-pic, as well as by -fPIC and -fpic without -mfdpic.  You
           should never have to use it explicitly.

       -mlinked-fp
           Follow the EABI requirement of always creating a frame pointer
           whenever a stack frame is allocated.  This option is enabled by
           default and can be disabled with -mno-linked-fp.

       -mlong-calls
           Use indirect addressing to call functions outside the current
           compilation unit.  This allows the functions to be placed anywhere
           within the 32-bit address space.

       -malign-labels
           Try to align labels to an 8-byte boundary by inserting NOPs into the
           previous packet.  This option only has an effect when VLIW packing is
           enabled.  It doesn't create new packets; it merely adds NOPs to
           existing ones.

       -mlibrary-pic
           Generate position-independent EABI code.

       -macc-4
           Use only the first four media accumulator registers.

       -macc-8
           Use all eight media accumulator registers.

       -mpack
           Pack VLIW instructions.

       -mno-pack
           Do not pack VLIW instructions.

       -mno-eflags
           Do not mark ABI switches in e_flags.

       -mcond-move
           Enable the use of conditional-move instructions (default).

           This switch is mainly for debugging the compiler and will likely be
           removed in a future version.

       -mno-cond-move
           Disable the use of conditional-move instructions.

           This switch is mainly for debugging the compiler and will likely be
           removed in a future version.

       -mscc
           Enable the use of conditional set instructions (default).

           This switch is mainly for debugging the compiler and will likely be
           removed in a future version.

       -mno-scc
           Disable the use of conditional set instructions.

           This switch is mainly for debugging the compiler and will likely be
           removed in a future version.

       -mcond-exec
           Enable the use of conditional execution (default).

           This switch is mainly for debugging the compiler and will likely be
           removed in a future version.

       -mno-cond-exec
           Disable the use of conditional execution.

           This switch is mainly for debugging the compiler and will likely be
           removed in a future version.

       -mvliw-branch
           Run a pass to pack branches into VLIW instructions (default).

           This switch is mainly for debugging the compiler and will likely be
           removed in a future version.

       -mno-vliw-branch
           Do not run a pass to pack branches into VLIW instructions.

           This switch is mainly for debugging the compiler and will likely be
           removed in a future version.

       -mmulti-cond-exec
           Enable optimization of "&&" and "||" in conditional execution
           (default).

           This switch is mainly for debugging the compiler and will likely be
           removed in a future version.

       -mno-multi-cond-exec
           Disable optimization of "&&" and "||" in conditional execution.

           This switch is mainly for debugging the compiler and will likely be
           removed in a future version.

       -mnested-cond-exec
           Enable nested conditional execution optimizations (default).

           This switch is mainly for debugging the compiler and will likely be
           removed in a future version.

       -mno-nested-cond-exec
           Disable nested conditional execution optimizations.

           This switch is mainly for debugging the compiler and will likely be
           removed in a future version.

       -moptimize-membar
           This switch removes redundant "membar" instructions from the
           compiler-generated code.  It is enabled by default.

       -mno-optimize-membar
           This switch disables the automatic removal of redundant "membar"
           instructions from the generated code.

       -mtomcat-stats
           Cause gas to print out tomcat statistics.

       -mcpu=cpu
           Select the processor type for which to generate code.  Possible
           values are frv, fr550, tomcat, fr500, fr450, fr405, fr400, fr300 and
           simple.

       GNU/Linux Options

       These -m options are defined for GNU/Linux targets:

       -mglibc
           Use the GNU C library.  This is the default except on
           *-*-linux-*uclibc*, *-*-linux-*musl* and *-*-linux-*android* targets.

       -muclibc
           Use uClibc C library.  This is the default on *-*-linux-*uclibc*
           targets.

       -mmusl
           Use the musl C library.  This is the default on *-*-linux-*musl*
           targets.

       -mbionic
           Use Bionic C library.  This is the default on *-*-linux-*android*
           targets.

       -mandroid
           Compile code compatible with Android platform.  This is the default
           on *-*-linux-*android* targets.

           When compiling, this option enables -mbionic, -fPIC, -fno-exceptions
           and -fno-rtti by default.  When linking, this option makes the GCC
           driver pass Android-specific options to the linker.  Finally, this
           option causes the preprocessor macro "__ANDROID__" to be defined.

       -tno-android-cc
           Disable compilation effects of -mandroid, i.e., do not enable
           -mbionic, -fPIC, -fno-exceptions and -fno-rtti by default.

       -tno-android-ld
           Disable linking effects of -mandroid, i.e., pass standard Linux
           linking options to the linker.

       H8/300 Options

       These -m options are defined for the H8/300 implementations:

       -mrelax
           Shorten some address references at link time, when possible; uses the
           linker option -relax.

       -mh Generate code for the H8/300H.

       -ms Generate code for the H8S.

       -mn Generate code for the H8S and H8/300H in the normal mode.  This
           switch must be used either with -mh or -ms.

       -ms2600
           Generate code for the H8S/2600.  This switch must be used with -ms.

       -mexr
           Extended registers are stored on stack before execution of function
           with monitor attribute. Default option is -mexr.  This option is
           valid only for H8S targets.

       -mno-exr
           Extended registers are not stored on stack before execution of
           function with monitor attribute. Default option is -mno-exr.  This
           option is valid only for H8S targets.

       -mint32
           Make "int" data 32 bits by default.

       -malign-300
           On the H8/300H and H8S, use the same alignment rules as for the
           H8/300.  The default for the H8/300H and H8S is to align longs and
           floats on 4-byte boundaries.  -malign-300 causes them to be aligned
           on 2-byte boundaries.  This option has no effect on the H8/300.

       HPPA Options

       These -m options are defined for the HPPA family of computers:

       -march=architecture-type
           Generate code for the specified architecture.  The choices for
           architecture-type are 1.0 for PA 1.0, 1.1 for PA 1.1, and 2.0 for PA
           2.0 processors.  Refer to /usr/lib/sched.models on an HP-UX system to
           determine the proper architecture option for your machine.  Code
           compiled for lower numbered architectures runs on higher numbered
           architectures, but not the other way around.

       -mpa-risc-1-0
       -mpa-risc-1-1
       -mpa-risc-2-0
           Synonyms for -march=1.0, -march=1.1, and -march=2.0 respectively.

       -mcaller-copies
           The caller copies function arguments passed by hidden reference.
           This option should be used with care as it is not compatible with the
           default 32-bit runtime.  However, only aggregates larger than eight
           bytes are passed by hidden reference and the option provides better
           compatibility with OpenMP.

       -mjump-in-delay
           This option is ignored and provided for compatibility purposes only.

       -mdisable-fpregs
           Prevent floating-point registers from being used in any manner.  This
           is necessary for compiling kernels that perform lazy context
           switching of floating-point registers.  If you use this option and
           attempt to perform floating-point operations, the compiler aborts.

       -mdisable-indexing
           Prevent the compiler from using indexing address modes.  This avoids
           some rather obscure problems when compiling MIG generated code under
           MACH.

       -mno-space-regs
           Generate code that assumes the target has no space registers.  This
           allows GCC to generate faster indirect calls and use unscaled index
           address modes.

           Such code is suitable for level 0 PA systems and kernels.

       -mfast-indirect-calls
           Generate code that assumes calls never cross space boundaries.  This
           allows GCC to emit code that performs faster indirect calls.

           This option does not work in the presence of shared libraries or
           nested functions.

       -mfixed-range=register-range
           Generate code treating the given register range as fixed registers.
           A fixed register is one that the register allocator cannot use.  This
           is useful when compiling kernel code.  A register range is specified
           as two registers separated by a dash.  Multiple register ranges can
           be specified separated by a comma.

       -mlong-load-store
           Generate 3-instruction load and store sequences as sometimes required
           by the HP-UX 10 linker.  This is equivalent to the +k option to the
           HP compilers.

       -mportable-runtime
           Use the portable calling conventions proposed by HP for ELF systems.

       -mgas
           Enable the use of assembler directives only GAS understands.

       -mschedule=cpu-type
           Schedule code according to the constraints for the machine type cpu-
           type.  The choices for cpu-type are 700 7100, 7100LC, 7200, 7300 and
           8000.  Refer to /usr/lib/sched.models on an HP-UX system to determine
           the proper scheduling option for your machine.  The default
           scheduling is 8000.

       -mlinker-opt
           Enable the optimization pass in the HP-UX linker.  Note this makes
           symbolic debugging impossible.  It also triggers a bug in the HP-UX 8
           and HP-UX 9 linkers in which they give bogus error messages when
           linking some programs.

       -msoft-float
           Generate output containing library calls for floating point.
           Warning: the requisite libraries are not available for all HPPA
           targets.  Normally the facilities of the machine's usual C compiler
           are used, but this cannot be done directly in cross-compilation.  You
           must make your own arrangements to provide suitable library functions
           for cross-compilation.

           -msoft-float changes the calling convention in the output file;
           therefore, it is only useful if you compile all of a program with
           this option.  In particular, you need to compile libgcc.a, the
           library that comes with GCC, with -msoft-float in order for this to
           work.

       -msio
           Generate the predefine, "_SIO", for server IO.  The default is
           -mwsio.  This generates the predefines, "__hp9000s700",
           "__hp9000s700__" and "_WSIO", for workstation IO.  These options are
           available under HP-UX and HI-UX.

       -mgnu-ld
           Use options specific to GNU ld.  This passes -shared to ld when
           building a shared library.  It is the default when GCC is configured,
           explicitly or implicitly, with the GNU linker.  This option does not
           affect which ld is called; it only changes what parameters are passed
           to that ld.  The ld that is called is determined by the --with-ld
           configure option, GCC's program search path, and finally by the
           user's PATH.  The linker used by GCC can be printed using which `gcc
           -print-prog-name=ld`.  This option is only available on the 64-bit
           HP-UX GCC, i.e. configured with hppa*64*-*-hpux*.

       -mhp-ld
           Use options specific to HP ld.  This passes -b to ld when building a
           shared library and passes +Accept TypeMismatch to ld on all links.
           It is the default when GCC is configured, explicitly or implicitly,
           with the HP linker.  This option does not affect which ld is called;
           it only changes what parameters are passed to that ld.  The ld that
           is called is determined by the --with-ld configure option, GCC's
           program search path, and finally by the user's PATH.  The linker used
           by GCC can be printed using which `gcc -print-prog-name=ld`.  This
           option is only available on the 64-bit HP-UX GCC, i.e. configured
           with hppa*64*-*-hpux*.

       -mlong-calls
           Generate code that uses long call sequences.  This ensures that a
           call is always able to reach linker generated stubs.  The default is
           to generate long calls only when the distance from the call site to
           the beginning of the function or translation unit, as the case may
           be, exceeds a predefined limit set by the branch type being used.
           The limits for normal calls are 7,600,000 and 240,000 bytes,
           respectively for the PA 2.0 and PA 1.X architectures.  Sibcalls are
           always limited at 240,000 bytes.

           Distances are measured from the beginning of functions when using the
           -ffunction-sections option, or when using the -mgas and
           -mno-portable-runtime options together under HP-UX with the SOM
           linker.

           It is normally not desirable to use this option as it degrades
           performance.  However, it may be useful in large applications,
           particularly when partial linking is used to build the application.

           The types of long calls used depends on the capabilities of the
           assembler and linker, and the type of code being generated.  The
           impact on systems that support long absolute calls, and long pic
           symbol-difference or pc-relative calls should be relatively small.
           However, an indirect call is used on 32-bit ELF systems in pic code
           and it is quite long.

       -munix=unix-std
           Generate compiler predefines and select a startfile for the specified
           UNIX standard.  The choices for unix-std are 93, 95 and 98.  93 is
           supported on all HP-UX versions.  95 is available on HP-UX 10.10 and
           later.  98 is available on HP-UX 11.11 and later.  The default values
           are 93 for HP-UX 10.00, 95 for HP-UX 10.10 though to 11.00, and 98
           for HP-UX 11.11 and later.

           -munix=93 provides the same predefines as GCC 3.3 and 3.4.  -munix=95
           provides additional predefines for "XOPEN_UNIX" and
           "_XOPEN_SOURCE_EXTENDED", and the startfile unix95.o.  -munix=98
           provides additional predefines for "_XOPEN_UNIX",
           "_XOPEN_SOURCE_EXTENDED", "_INCLUDE__STDC_A1_SOURCE" and
           "_INCLUDE_XOPEN_SOURCE_500", and the startfile unix98.o.

           It is important to note that this option changes the interfaces for
           various library routines.  It also affects the operational behavior
           of the C library.  Thus, extreme care is needed in using this option.

           Library code that is intended to operate with more than one UNIX
           standard must test, set and restore the variable
           "__xpg4_extended_mask" as appropriate.  Most GNU software doesn't
           provide this capability.

       -nolibdld
           Suppress the generation of link options to search libdld.sl when the
           -static option is specified on HP-UX 10 and later.

       -static
           The HP-UX implementation of setlocale in libc has a dependency on
           libdld.sl.  There isn't an archive version of libdld.sl.  Thus, when
           the -static option is specified, special link options are needed to
           resolve this dependency.

           On HP-UX 10 and later, the GCC driver adds the necessary options to
           link with libdld.sl when the -static option is specified.  This
           causes the resulting binary to be dynamic.  On the 64-bit port, the
           linkers generate dynamic binaries by default in any case.  The
           -nolibdld option can be used to prevent the GCC driver from adding
           these link options.

       -threads
           Add support for multithreading with the dce thread library under HP-
           UX.  This option sets flags for both the preprocessor and linker.

       IA-64 Options

       These are the -m options defined for the Intel IA-64 architecture.

       -mbig-endian
           Generate code for a big-endian target.  This is the default for HP-
           UX.

       -mlittle-endian
           Generate code for a little-endian target.  This is the default for
           AIX5 and GNU/Linux.

       -mgnu-as
       -mno-gnu-as
           Generate (or don't) code for the GNU assembler.  This is the default.

       -mgnu-ld
       -mno-gnu-ld
           Generate (or don't) code for the GNU linker.  This is the default.

       -mno-pic
           Generate code that does not use a global pointer register.  The
           result is not position independent code, and violates the IA-64 ABI.

       -mvolatile-asm-stop
       -mno-volatile-asm-stop
           Generate (or don't) a stop bit immediately before and after volatile
           asm statements.

       -mregister-names
       -mno-register-names
           Generate (or don't) in, loc, and out register names for the stacked
           registers.  This may make assembler output more readable.

       -mno-sdata
       -msdata
           Disable (or enable) optimizations that use the small data section.
           This may be useful for working around optimizer bugs.

       -mconstant-gp
           Generate code that uses a single constant global pointer value.  This
           is useful when compiling kernel code.

       -mauto-pic
           Generate code that is self-relocatable.  This implies -mconstant-gp.
           This is useful when compiling firmware code.

       -minline-float-divide-min-latency
           Generate code for inline divides of floating-point values using the
           minimum latency algorithm.

       -minline-float-divide-max-throughput
           Generate code for inline divides of floating-point values using the
           maximum throughput algorithm.

       -mno-inline-float-divide
           Do not generate inline code for divides of floating-point values.

       -minline-int-divide-min-latency
           Generate code for inline divides of integer values using the minimum
           latency algorithm.

       -minline-int-divide-max-throughput
           Generate code for inline divides of integer values using the maximum
           throughput algorithm.

       -mno-inline-int-divide
           Do not generate inline code for divides of integer values.

       -minline-sqrt-min-latency
           Generate code for inline square roots using the minimum latency
           algorithm.

       -minline-sqrt-max-throughput
           Generate code for inline square roots using the maximum throughput
           algorithm.

       -mno-inline-sqrt
           Do not generate inline code for "sqrt".

       -mfused-madd
       -mno-fused-madd
           Do (don't) generate code that uses the fused multiply/add or
           multiply/subtract instructions.  The default is to use these
           instructions.

       -mno-dwarf2-asm
       -mdwarf2-asm
           Don't (or do) generate assembler code for the DWARF line number
           debugging info.  This may be useful when not using the GNU assembler.

       -mearly-stop-bits
       -mno-early-stop-bits
           Allow stop bits to be placed earlier than immediately preceding the
           instruction that triggered the stop bit.  This can improve
           instruction scheduling, but does not always do so.

       -mfixed-range=register-range
           Generate code treating the given register range as fixed registers.
           A fixed register is one that the register allocator cannot use.  This
           is useful when compiling kernel code.  A register range is specified
           as two registers separated by a dash.  Multiple register ranges can
           be specified separated by a comma.

       -mtls-size=tls-size
           Specify bit size of immediate TLS offsets.  Valid values are 14, 22,
           and 64.

       -mtune=cpu-type
           Tune the instruction scheduling for a particular CPU, Valid values
           are itanium, itanium1, merced, itanium2, and mckinley.

       -milp32
       -mlp64
           Generate code for a 32-bit or 64-bit environment.  The 32-bit
           environment sets int, long and pointer to 32 bits.  The 64-bit
           environment sets int to 32 bits and long and pointer to 64 bits.
           These are HP-UX specific flags.

       -mno-sched-br-data-spec
       -msched-br-data-spec
           (Dis/En)able data speculative scheduling before reload.  This results
           in generation of "ld.a" instructions and the corresponding check
           instructions ("ld.c" / "chk.a").  The default setting is disabled.

       -msched-ar-data-spec
       -mno-sched-ar-data-spec
           (En/Dis)able data speculative scheduling after reload.  This results
           in generation of "ld.a" instructions and the corresponding check
           instructions ("ld.c" / "chk.a").  The default setting is enabled.

       -mno-sched-control-spec
       -msched-control-spec
           (Dis/En)able control speculative scheduling.  This feature is
           available only during region scheduling (i.e. before reload).  This
           results in generation of the "ld.s" instructions and the
           corresponding check instructions "chk.s".  The default setting is
           disabled.

       -msched-br-in-data-spec
       -mno-sched-br-in-data-spec
           (En/Dis)able speculative scheduling of the instructions that are
           dependent on the data speculative loads before reload.  This is
           effective only with -msched-br-data-spec enabled.  The default
           setting is enabled.

       -msched-ar-in-data-spec
       -mno-sched-ar-in-data-spec
           (En/Dis)able speculative scheduling of the instructions that are
           dependent on the data speculative loads after reload.  This is
           effective only with -msched-ar-data-spec enabled.  The default
           setting is enabled.

       -msched-in-control-spec
       -mno-sched-in-control-spec
           (En/Dis)able speculative scheduling of the instructions that are
           dependent on the control speculative loads.  This is effective only
           with -msched-control-spec enabled.  The default setting is enabled.

       -mno-sched-prefer-non-data-spec-insns
       -msched-prefer-non-data-spec-insns
           If enabled, data-speculative instructions are chosen for schedule
           only if there are no other choices at the moment.  This makes the use
           of the data speculation much more conservative.  The default setting
           is disabled.

       -mno-sched-prefer-non-control-spec-insns
       -msched-prefer-non-control-spec-insns
           If enabled, control-speculative instructions are chosen for schedule
           only if there are no other choices at the moment.  This makes the use
           of the control speculation much more conservative.  The default
           setting is disabled.

       -mno-sched-count-spec-in-critical-path
       -msched-count-spec-in-critical-path
           If enabled, speculative dependencies are considered during
           computation of the instructions priorities.  This makes the use of
           the speculation a bit more conservative.  The default setting is
           disabled.

       -msched-spec-ldc
           Use a simple data speculation check.  This option is on by default.

       -msched-control-spec-ldc
           Use a simple check for control speculation.  This option is on by
           default.

       -msched-stop-bits-after-every-cycle
           Place a stop bit after every cycle when scheduling.  This option is
           on by default.

       -msched-fp-mem-deps-zero-cost
           Assume that floating-point stores and loads are not likely to cause a
           conflict when placed into the same instruction group.  This option is
           disabled by default.

       -msel-sched-dont-check-control-spec
           Generate checks for control speculation in selective scheduling.
           This flag is disabled by default.

       -msched-max-memory-insns=max-insns
           Limit on the number of memory insns per instruction group, giving
           lower priority to subsequent memory insns attempting to schedule in
           the same instruction group. Frequently useful to prevent cache bank
           conflicts.  The default value is 1.

       -msched-max-memory-insns-hard-limit
           Makes the limit specified by msched-max-memory-insns a hard limit,
           disallowing more than that number in an instruction group.
           Otherwise, the limit is "soft", meaning that non-memory operations
           are preferred when the limit is reached, but memory operations may
           still be scheduled.

       LM32 Options

       These -m options are defined for the LatticeMico32 architecture:

       -mbarrel-shift-enabled
           Enable barrel-shift instructions.

       -mdivide-enabled
           Enable divide and modulus instructions.

       -mmultiply-enabled
           Enable multiply instructions.

       -msign-extend-enabled
           Enable sign extend instructions.

       -muser-enabled
           Enable user-defined instructions.

       M32C Options

       -mcpu=name
           Select the CPU for which code is generated.  name may be one of r8c
           for the R8C/Tiny series, m16c for the M16C (up to /60) series, m32cm
           for the M16C/80 series, or m32c for the M32C/80 series.

       -msim
           Specifies that the program will be run on the simulator.  This causes
           an alternate runtime library to be linked in which supports, for
           example, file I/O.  You must not use this option when generating
           programs that will run on real hardware; you must provide your own
           runtime library for whatever I/O functions are needed.

       -memregs=number
           Specifies the number of memory-based pseudo-registers GCC uses during
           code generation.  These pseudo-registers are used like real
           registers, so there is a tradeoff between GCC's ability to fit the
           code into available registers, and the performance penalty of using
           memory instead of registers.  Note that all modules in a program must
           be compiled with the same value for this option.  Because of that,
           you must not use this option with GCC's default runtime libraries.

       M32R/D Options

       These -m options are defined for Renesas M32R/D architectures:

       -m32r2
           Generate code for the M32R/2.

       -m32rx
           Generate code for the M32R/X.

       -m32r
           Generate code for the M32R.  This is the default.

       -mmodel=small
           Assume all objects live in the lower 16MB of memory (so that their
           addresses can be loaded with the "ld24" instruction), and assume all
           subroutines are reachable with the "bl" instruction.  This is the
           default.

           The addressability of a particular object can be set with the "model"
           attribute.

       -mmodel=medium
           Assume objects may be anywhere in the 32-bit address space (the
           compiler generates "seth/add3" instructions to load their addresses),
           and assume all subroutines are reachable with the "bl" instruction.

       -mmodel=large
           Assume objects may be anywhere in the 32-bit address space (the
           compiler generates "seth/add3" instructions to load their addresses),
           and assume subroutines may not be reachable with the "bl" instruction
           (the compiler generates the much slower "seth/add3/jl" instruction
           sequence).

       -msdata=none
           Disable use of the small data area.  Variables are put into one of
           ".data", ".bss", or ".rodata" (unless the "section" attribute has
           been specified).  This is the default.

           The small