VALGRIND(1)                         valgrind                         VALGRIND(1)

       valgrind - a suite of tools for debugging and profiling programs

       valgrind [valgrind-options] [your-program] [your-program-options]

       Valgrind is a flexible program for debugging and profiling Linux
       executables. It consists of a core, which provides a synthetic CPU in
       software, and a series of debugging and profiling tools. The architecture
       is modular, so that new tools can be created easily and without
       disturbing the existing structure.

       Some of the options described below work with all Valgrind tools, and
       some only work with a few or one. The section MEMCHECK OPTIONS and those
       below it describe tool-specific options.

       This manual page covers only basic usage and options. For more
       comprehensive information, please see the HTML documentation on your
       system: $INSTALL/share/doc/valgrind/html/index.html, or online:

       The single most important option.

       --tool=<toolname> [default: memcheck]
           Run the Valgrind tool called toolname, e.g. memcheck, cachegrind,
           callgrind, helgrind, drd, massif, dhat, lackey, none, exp-bbv, etc.

       These options work with all tools.

       -h --help
           Show help for all options, both for the core and for the selected
           tool. If the option is repeated it is equivalent to giving

           Same as --help, but also lists debugging options which usually are
           only of use to Valgrind's developers.

           Show the version number of the Valgrind core. Tools can have their
           own version numbers. There is a scheme in place to ensure that tools
           only execute when the core version is one they are known to work
           with. This was done to minimise the chances of strange problems
           arising from tool-vs-core version incompatibilities.

       -q, --quiet
           Run silently, and only print error messages. Useful if you are
           running regression tests or have some other automated test machinery.

       -v, --verbose
           Be more verbose. Gives extra information on various aspects of your
           program, such as: the shared objects loaded, the suppressions used,
           the progress of the instrumentation and execution engines, and
           warnings about unusual behaviour. Repeating the option increases the
           verbosity level.

       --trace-children=<yes|no> [default: no]
           When enabled, Valgrind will trace into sub-processes initiated via
           the exec system call. This is necessary for multi-process programs.

           Note that Valgrind does trace into the child of a fork (it would be
           difficult not to, since fork makes an identical copy of a process),
           so this option is arguably badly named. However, most children of
           fork calls immediately call exec anyway.

           This option only has an effect when --trace-children=yes is
           specified. It allows for some children to be skipped. The option
           takes a comma separated list of patterns for the names of child
           executables that Valgrind should not trace into. Patterns may include
           the metacharacters ?  and *, which have the usual meaning.

           This can be useful for pruning uninteresting branches from a tree of
           processes being run on Valgrind. But you should be careful when using
           it. When Valgrind skips tracing into an executable, it doesn't just
           skip tracing that executable, it also skips tracing any of that
           executable's child processes. In other words, the flag doesn't merely
           cause tracing to stop at the specified executables -- it skips
           tracing of entire process subtrees rooted at any of the specified

           This is the same as --trace-children-skip, with one difference: the
           decision as to whether to trace into a child process is made by
           examining the arguments to the child process, rather than the name of
           its executable.

       --child-silent-after-fork=<yes|no> [default: no]
           When enabled, Valgrind will not show any debugging or logging output
           for the child process resulting from a fork call. This can make the
           output less confusing (although more misleading) when dealing with
           processes that create children. It is particularly useful in
           conjunction with --trace-children=. Use of this option is also
           strongly recommended if you are requesting XML output (--xml=yes),
           since otherwise the XML from child and parent may become mixed up,
           which usually makes it useless.

       --vgdb=<no|yes|full> [default: yes]
           Valgrind will provide "gdbserver" functionality when --vgdb=yes or
           --vgdb=full is specified. This allows an external GNU GDB debugger to
           control and debug your program when it runs on Valgrind.  --vgdb=full
           incurs significant performance overheads, but provides more precise
           breakpoints and watchpoints. See Debugging your program using
           Valgrind's gdbserver and GDB for a detailed description.

           If the embedded gdbserver is enabled but no gdb is currently being
           used, the vgdb command line utility can send "monitor commands" to
           Valgrind from a shell. The Valgrind core provides a set of Valgrind
           monitor commands. A tool can optionally provide tool specific monitor
           commands, which are documented in the tool specific chapter.

       --vgdb-error=<number> [default: 999999999]
           Use this option when the Valgrind gdbserver is enabled with
           --vgdb=yes or --vgdb=full. Tools that report errors will wait for
           "number" errors to be reported before freezing the program and
           waiting for you to connect with GDB. It follows that a value of zero
           will cause the gdbserver to be started before your program is
           executed. This is typically used to insert GDB breakpoints before
           execution, and also works with tools that do not report errors, such
           as Massif.

       --vgdb-stop-at=<set> [default: none]
           Use this option when the Valgrind gdbserver is enabled with
           --vgdb=yes or --vgdb=full. The Valgrind gdbserver will be invoked for
           each error after --vgdb-error have been reported. You can
           additionally ask the Valgrind gdbserver to be invoked for other
           events, specified in one of the following ways:

           •   a comma separated list of one or more of startup exit

               The values startup exit valgrindabexit respectively indicate to
               invoke gdbserver before your program is executed, after the last
               instruction of your program, on Valgrind abnormal exit (e.g.
               internal error, out of memory, ...).

               Note: startup and --vgdb-error=0 will both cause Valgrind
               gdbserver to be invoked before your program is executed. The
               --vgdb-error=0 will in addition cause your program to stop on all
               subsequent errors.

           •   all to specify the complete set. It is equivalent to

           •   none for the empty set.

       --track-fds=<yes|no|all> [default: no]
           When enabled, Valgrind will print out a list of open file descriptors
           on exit or on request, via the gdbserver monitor command
           open_fds. Along with each file descriptor is printed a stack
           backtrace of where the file was opened and any details relating to
           the file descriptor such as the file name or socket details. Use all
           to include reporting on stdin, stdout and stderr.

       --time-stamp=<yes|no> [default: no]
           When enabled, each message is preceded with an indication of the
           elapsed wallclock time since startup, expressed as days, hours,
           minutes, seconds and milliseconds.

       --log-fd=<number> [default: 2, stderr]
           Specifies that Valgrind should send all of its messages to the
           specified file descriptor. The default, 2, is the standard error
           channel (stderr). Note that this may interfere with the client's own
           use of stderr, as Valgrind's output will be interleaved with any
           output that the client sends to stderr.

           Specifies that Valgrind should send all of its messages to the
           specified file. If the file name is empty, it causes an abort. There
           are three special format specifiers that can be used in the file

           %p is replaced with the current process ID. This is very useful for
           program that invoke multiple processes. WARNING: If you use
           --trace-children=yes and your program invokes multiple processes OR
           your program forks without calling exec afterwards, and you don't use
           this specifier (or the %q specifier below), the Valgrind output from
           all those processes will go into one file, possibly jumbled up, and
           possibly incomplete. Note: If the program forks and calls exec
           afterwards, Valgrind output of the child from the period between fork
           and exec will be lost. Fortunately this gap is really tiny for most
           programs; and modern programs use posix_spawn anyway.

           %n is replaced with a file sequence number unique for this process.
           This is useful for processes that produces several files from the
           same filename template.

           %q{FOO} is replaced with the contents of the environment variable
           FOO. If the {FOO} part is malformed, it causes an abort. This
           specifier is rarely needed, but very useful in certain circumstances
           (eg. when running MPI programs). The idea is that you specify a
           variable which will be set differently for each process in the job,
           for example BPROC_RANK or whatever is applicable in your MPI setup.
           If the named environment variable is not set, it causes an abort.
           Note that in some shells, the { and } characters may need to be
           escaped with a backslash.

           %% is replaced with %.

           If an % is followed by any other character, it causes an abort.

           If the file name specifies a relative file name, it is put in the
           program's initial working directory: this is the current directory
           when the program started its execution after the fork or after the
           exec. If it specifies an absolute file name (ie. starts with '/')
           then it is put there.

           Specifies that Valgrind should send all of its messages to the
           specified port at the specified IP address. The port may be omitted,
           in which case port 1500 is used. If a connection cannot be made to
           the specified socket, Valgrind falls back to writing output to the
           standard error (stderr). This option is intended to be used in
           conjunction with the valgrind-listener program. For further details,
           see the commentary in the manual.

       These options are used by all tools that can report errors, e.g.
       Memcheck, but not Cachegrind.

       --xml=<yes|no> [default: no]
           When enabled, the important parts of the output (e.g. tool error
           messages) will be in XML format rather than plain text. Furthermore,
           the XML output will be sent to a different output channel than the
           plain text output. Therefore, you also must use one of --xml-fd,
           --xml-file or --xml-socket to specify where the XML is to be sent.

           Less important messages will still be printed in plain text, but
           because the XML output and plain text output are sent to different
           output channels (the destination of the plain text output is still
           controlled by --log-fd, --log-file and --log-socket) this should not
           cause problems.

           This option is aimed at making life easier for tools that consume
           Valgrind's output as input, such as GUI front ends. Currently this
           option works with Memcheck, Helgrind and DRD. The output format is
           specified in the file docs/internals/xml-output-protocol4.txt in the
           source tree for Valgrind 3.5.0 or later.

           The recommended options for a GUI to pass, when requesting XML
           output, are: --xml=yes to enable XML output, --xml-file to send the
           XML output to a (presumably GUI-selected) file, --log-file to send
           the plain text output to a second GUI-selected file,
           --child-silent-after-fork=yes, and -q to restrict the plain text
           output to critical error messages created by Valgrind itself. For
           example, failure to read a specified suppressions file counts as a
           critical error message. In this way, for a successful run the text
           output file will be empty. But if it isn't empty, then it will
           contain important information which the GUI user should be made aware

       --xml-fd=<number> [default: -1, disabled]
           Specifies that Valgrind should send its XML output to the specified
           file descriptor. It must be used in conjunction with --xml=yes.

           Specifies that Valgrind should send its XML output to the specified
           file. It must be used in conjunction with --xml=yes. Any %p or %q
           sequences appearing in the filename are expanded in exactly the same
           way as they are for --log-file. See the description of --log-file for

           Specifies that Valgrind should send its XML output the specified port
           at the specified IP address. It must be used in conjunction with
           --xml=yes. The form of the argument is the same as that used by
           --log-socket. See the description of --log-socket for further

           Embeds an extra user comment string at the start of the XML output.
           Only works when --xml=yes is specified; ignored otherwise.

       --demangle=<yes|no> [default: yes]
           Enable/disable automatic demangling (decoding) of C++ names. Enabled
           by default. When enabled, Valgrind will attempt to translate encoded
           C++ names back to something approaching the original. The demangler
           handles symbols mangled by g++ versions 2.X, 3.X and 4.X.

           An important fact about demangling is that function names mentioned
           in suppressions files should be in their mangled form. Valgrind does
           not demangle function names when searching for applicable
           suppressions, because to do otherwise would make suppression file
           contents dependent on the state of Valgrind's demangling machinery,
           and also slow down suppression matching.

       --num-callers=<number> [default: 12]
           Specifies the maximum number of entries shown in stack traces that
           identify program locations. Note that errors are commoned up using
           only the top four function locations (the place in the current
           function, and that of its three immediate callers). So this doesn't
           affect the total number of errors reported.

           The maximum value for this is 500. Note that higher settings will
           make Valgrind run a bit more slowly and take a bit more memory, but
           can be useful when working with programs with deeply-nested call

       --unw-stack-scan-thresh=<number> [default: 0] ,
       --unw-stack-scan-frames=<number> [default: 5]
           Stack-scanning support is available only on ARM targets.

           These flags enable and control stack unwinding by stack scanning.
           When the normal stack unwinding mechanisms -- usage of Dwarf CFI
           records, and frame-pointer following -- fail, stack scanning may be
           able to recover a stack trace.

           Note that stack scanning is an imprecise, heuristic mechanism that
           may give very misleading results, or none at all. It should be used
           only in emergencies, when normal unwinding fails, and it is important
           to nevertheless have stack traces.

           Stack scanning is a simple technique: the unwinder reads words from
           the stack, and tries to guess which of them might be return
           addresses, by checking to see if they point just after ARM or Thumb
           call instructions. If so, the word is added to the backtrace.

           The main danger occurs when a function call returns, leaving its
           return address exposed, and a new function is called, but the new
           function does not overwrite the old address. The result of this is
           that the backtrace may contain entries for functions which have
           already returned, and so be very confusing.

           A second limitation of this implementation is that it will scan only
           the page (4KB, normally) containing the starting stack pointer. If
           the stack frames are large, this may result in only a few (or not
           even any) being present in the trace. Also, if you are unlucky and
           have an initial stack pointer near the end of its containing page,
           the scan may miss all interesting frames.

           By default stack scanning is disabled. The normal use case is to ask
           for it when a stack trace would otherwise be very short. So, to
           enable it, use --unw-stack-scan-thresh=number. This requests Valgrind
           to try using stack scanning to "extend" stack traces which contain
           fewer than number frames.

           If stack scanning does take place, it will only generate at most the
           number of frames specified by --unw-stack-scan-frames. Typically,
           stack scanning generates so many garbage entries that this value is
           set to a low value (5) by default. In no case will a stack trace
           larger than the value specified by --num-callers be created.

       --error-limit=<yes|no> [default: yes]
           When enabled, Valgrind stops reporting errors after 10,000,000 in
           total, or 1,000 different ones, have been seen. This is to stop the
           error tracking machinery from becoming a huge performance overhead in
           programs with many errors.

       --error-exitcode=<number> [default: 0]
           Specifies an alternative exit code to return if Valgrind reported any
           errors in the run. When set to the default value (zero), the return
           value from Valgrind will always be the return value of the process
           being simulated. When set to a nonzero value, that value is returned
           instead, if Valgrind detects any errors. This is useful for using
           Valgrind as part of an automated test suite, since it makes it easy
           to detect test cases for which Valgrind has reported errors, just by
           inspecting return codes.

       --exit-on-first-error=<yes|no> [default: no]
           If this option is enabled, Valgrind exits on the first error. A
           nonzero exit value must be defined using --error-exitcode option.
           Useful if you are running regression tests or have some other
           automated test machinery.

       --error-markers=<begin>,<end> [default: none]
           When errors are output as plain text (i.e. XML not used),
           --error-markers instructs to output a line containing the begin (end)
           string before (after) each error.

           Such marker lines facilitate searching for errors and/or extracting
           errors in an output file that contain valgrind errors mixed with the
           program output.

           Note that empty markers are accepted. So, only using a begin (or an
           end) marker is possible.

       --show-error-list=no|yes [default: no]
           If this option is enabled, for tools that report errors, valgrind
           will show the list of detected errors and the list of used
           suppressions at exit.

           Note that at verbosity 2 and above, valgrind automatically shows the
           list of detected errors and the list of used suppressions at exit,
           unless --show-error-list=no is selected.

           Specifying -s is equivalent to --show-error-list=yes.

       --sigill-diagnostics=<yes|no> [default: yes]
           Enable/disable printing of illegal instruction diagnostics. Enabled
           by default, but defaults to disabled when --quiet is given. The
           default can always be explicitly overridden by giving this option.

           When enabled, a warning message will be printed, along with some
           diagnostics, whenever an instruction is encountered that Valgrind
           cannot decode or translate, before the program is given a SIGILL
           signal. Often an illegal instruction indicates a bug in the program
           or missing support for the particular instruction in Valgrind. But
           some programs do deliberately try to execute an instruction that
           might be missing and trap the SIGILL signal to detect processor
           features. Using this flag makes it possible to avoid the diagnostic
           output that you would otherwise get in such cases.

       --keep-debuginfo=<yes|no> [default: no]
           When enabled, keep ("archive") symbols and all other debuginfo for
           unloaded code. This allows saved stack traces to include file/line
           info for code that has been dlclose'd (or similar). Be careful with
           this, since it can lead to unbounded memory use for programs which
           repeatedly load and unload shared objects.

           Some tools and some functionalities have only limited support for
           archived debug info. Memcheck fully supports it. Generally, tools
           that report errors can use archived debug info to show the error
           stack traces. The known limitations are: Helgrind's past access stack
           trace of a race condition is does not use archived debug info. Massif
           (and more generally the xtree Massif output format) does not make use
           of archived debug info. Only Memcheck has been (somewhat) tested with
           --keep-debuginfo=yes, so other tools may have unknown limitations.

       --show-below-main=<yes|no> [default: no]
           By default, stack traces for errors do not show any functions that
           appear beneath main because most of the time it's uninteresting C
           library stuff and/or gobbledygook. Alternatively, if main is not
           present in the stack trace, stack traces will not show any functions
           below main-like functions such as glibc's __libc_start_main.
           Furthermore, if main-like functions are present in the trace, they
           are normalised as (below main), in order to make the output more

           If this option is enabled, all stack trace entries will be shown and
           main-like functions will not be normalised.

       --fullpath-after=<string> [default: don't show source paths]
           By default Valgrind only shows the filenames in stack traces, but not
           full paths to source files. When using Valgrind in large projects
           where the sources reside in multiple different directories, this can
           be inconvenient.  --fullpath-after provides a flexible solution to
           this problem. When this option is present, the path to each source
           file is shown, with the following all-important caveat: if string is
           found in the path, then the path up to and including string is
           omitted, else the path is shown unmodified. Note that string is not
           required to be a prefix of the path.

           For example, consider a file named
           /home/janedoe/blah/src/foo/bar/xyzzy.c. Specifying
           --fullpath-after=/home/janedoe/blah/src/ will cause Valgrind to show
           the name as foo/bar/xyzzy.c.

           Because the string is not required to be a prefix,
           --fullpath-after=src/ will produce the same output. This is useful
           when the path contains arbitrary machine-generated characters. For
           example, the path /my/build/dir/C32A1B47/blah/src/foo/xyzzy can be
           pruned to foo/xyzzy using --fullpath-after=/blah/src/.

           If you simply want to see the full path, just specify an empty
           string: --fullpath-after=. This isn't a special case, merely a
           logical consequence of the above rules.

           Finally, you can use --fullpath-after multiple times. Any appearance
           of it causes Valgrind to switch to producing full paths and applying
           the above filtering rule. Each produced path is compared against all
           the --fullpath-after-specified strings, in the order specified. The
           first string to match causes the path to be truncated as described
           above. If none match, the full path is shown. This facilitates
           chopping off prefixes when the sources are drawn from a number of
           unrelated directories.

       --extra-debuginfo-path=<path> [default: undefined and unused]
           By default Valgrind searches in several well-known paths for debug
           objects, such as /usr/lib/debug/.

           However, there may be scenarios where you may wish to put debug
           objects at an arbitrary location, such as external storage when
           running Valgrind on a mobile device with limited local storage.
           Another example might be a situation where you do not have permission
           to install debug object packages on the system where you are running

           In these scenarios, you may provide an absolute path as an extra,
           final place for Valgrind to search for debug objects by specifying
           --extra-debuginfo-path=/path/to/debug/objects. The given path will be
           prepended to the absolute path name of the searched-for object. For
           example, if Valgrind is looking for the debuginfo for /w/x/y/
           and --extra-debuginfo-path=/a/b/c is specified, it will look for a
           debug object at /a/b/c/w/x/y/

           This flag should only be specified once. If it is specified multiple
           times, only the last instance is honoured.

       --debuginfo-server=ipaddr:port [default: undefined and unused]
           This is a new, experimental, feature introduced in version 3.9.0.

           In some scenarios it may be convenient to read debuginfo from objects
           stored on a different machine. With this flag, Valgrind will query a
           debuginfo server running on ipaddr and listening on port port, if it
           cannot find the debuginfo object in the local filesystem.

           The debuginfo server must accept TCP connections on port port. The
           debuginfo server is contained in the source file
           auxprogs/valgrind-di-server.c. It will only serve from the directory
           it is started in.  port defaults to 1500 in both client and server if
           not specified.

           If Valgrind looks for the debuginfo for /w/x/y/ by using the
           debuginfo server, it will strip the pathname components and merely
           request on the server. That in turn will look only in its
           current working directory for a matching debuginfo object.

           The debuginfo data is transmitted in small fragments (8 KB) as
           requested by Valgrind. Each block is compressed using LZO to reduce
           transmission time. The implementation has been tuned for best
           performance over a single-stage 802.11g (WiFi) network link.

           Note that checks for matching primary vs debug objects, using GNU
           debuglink CRC scheme, are performed even when using the debuginfo
           server. To disable such checking, you need to also specify

           By default the Valgrind build system will build valgrind-di-server
           for the target platform, which is almost certainly not what you want.
           So far we have been unable to find out how to get automake/autoconf
           to build it for the build platform. If you want to use it, you will
           have to recompile it by hand using the command shown at the top of

           Valgrind can also download debuginfo via debuginfod. See the
           DEBUGINFOD section for more information.

       --allow-mismatched-debuginfo=no|yes [no]
           When reading debuginfo from separate debuginfo objects, Valgrind will
           by default check that the main and debuginfo objects match, using the
           GNU debuglink mechanism. This guarantees that it does not read
           debuginfo from out of date debuginfo objects, and also ensures that
           Valgrind can't crash as a result of mismatches.

           This check can be overridden using --allow-mismatched-debuginfo=yes.
           This may be useful when the debuginfo and main objects have not been
           split in the proper way. Be careful when using this, though: it
           disables all consistency checking, and Valgrind has been observed to
           crash when the main and debuginfo objects don't match.

       --suppressions=<filename> [default: $PREFIX/lib/valgrind/default.supp]
           Specifies an extra file from which to read descriptions of errors to
           suppress. You may use up to 100 extra suppression files.

       --gen-suppressions=<yes|no|all> [default: no]
           When set to yes, Valgrind will pause after every error shown and
           print the line:

                   ---- Print suppression ? --- [Return/N/n/Y/y/C/c] ----

           Pressing Ret, or N Ret or n Ret, causes Valgrind continue execution
           without printing a suppression for this error.

           Pressing Y Ret or y Ret causes Valgrind to write a suppression for
           this error. You can then cut and paste it into a suppression file if
           you don't want to hear about the error in the future.

           When set to all, Valgrind will print a suppression for every reported
           error, without querying the user.

           This option is particularly useful with C++ programs, as it prints
           out the suppressions with mangled names, as required.

           Note that the suppressions printed are as specific as possible. You
           may want to common up similar ones, by adding wildcards to function
           names, and by using frame-level wildcards. The wildcarding facilities
           are powerful yet flexible, and with a bit of careful editing, you may
           be able to suppress a whole family of related errors with only a few

           Sometimes two different errors are suppressed by the same
           suppression, in which case Valgrind will output the suppression more
           than once, but you only need to have one copy in your suppression
           file (but having more than one won't cause problems). Also, the
           suppression name is given as <insert a suppression name here>; the
           name doesn't really matter, it's only used with the -v option which
           prints out all used suppression records.

       --input-fd=<number> [default: 0, stdin]
           When using --gen-suppressions=yes, Valgrind will stop so as to read
           keyboard input from you when each error occurs. By default it reads
           from the standard input (stdin), which is problematic for programs
           which close stdin. This option allows you to specify an alternative
           file descriptor from which to read input.

       --dsymutil=no|yes [yes]
           This option is only relevant when running Valgrind on Mac OS X.

           Mac OS X uses a deferred debug information (debuginfo) linking
           scheme. When object files containing debuginfo are linked into a
           .dylib or an executable, the debuginfo is not copied into the final
           file. Instead, the debuginfo must be linked manually by running
           dsymutil, a system-provided utility, on the executable or .dylib. The
           resulting combined debuginfo is placed in a directory alongside the
           executable or .dylib, but with the extension .dSYM.

           With --dsymutil=no, Valgrind will detect cases where the .dSYM
           directory is either missing, or is present but does not appear to
           match the associated executable or .dylib, most likely because it is
           out of date. In these cases, Valgrind will print a warning message
           but take no further action.

           With --dsymutil=yes, Valgrind will, in such cases, automatically run
           dsymutil as necessary to bring the debuginfo up to date. For all
           practical purposes, if you always use --dsymutil=yes, then there is
           never any need to run dsymutil manually or as part of your
           applications's build system, since Valgrind will run it as necessary.

           Valgrind will not attempt to run dsymutil on any executable or
           library in /usr/, /bin/, /sbin/, /opt/, /sw/, /System/, /Library/ or
           /Applications/ since dsymutil will always fail in such situations. It
           fails both because the debuginfo for such pre-installed system
           components is not available anywhere, and also because it would
           require write privileges in those directories.

           Be careful when using --dsymutil=yes, since it will cause
           pre-existing .dSYM directories to be silently deleted and re-created.
           Also note that dsymutil is quite slow, sometimes excessively so.

       --max-stackframe=<number> [default: 2000000]
           The maximum size of a stack frame. If the stack pointer moves by more
           than this amount then Valgrind will assume that the program is
           switching to a different stack.

           You may need to use this option if your program has large
           stack-allocated arrays. Valgrind keeps track of your program's stack
           pointer. If it changes by more than the threshold amount, Valgrind
           assumes your program is switching to a different stack, and Memcheck
           behaves differently than it would for a stack pointer change smaller
           than the threshold. Usually this heuristic works well. However, if
           your program allocates large structures on the stack, this heuristic
           will be fooled, and Memcheck will subsequently report large numbers
           of invalid stack accesses. This option allows you to change the
           threshold to a different value.

           You should only consider use of this option if Valgrind's debug
           output directs you to do so. In that case it will tell you the new
           threshold you should specify.

           In general, allocating large structures on the stack is a bad idea,
           because you can easily run out of stack space, especially on systems
           with limited memory or which expect to support large numbers of
           threads each with a small stack, and also because the error checking
           performed by Memcheck is more effective for heap-allocated data than
           for stack-allocated data. If you have to use this option, you may
           wish to consider rewriting your code to allocate on the heap rather
           than on the stack.

       --main-stacksize=<number> [default: use current 'ulimit' value]
           Specifies the size of the main thread's stack.

           To simplify its memory management, Valgrind reserves all required
           space for the main thread's stack at startup. That means it needs to
           know the required stack size at startup.

           By default, Valgrind uses the current "ulimit" value for the stack
           size, or 16 MB, whichever is lower. In many cases this gives a stack
           size in the range 8 to 16 MB, which almost never overflows for most

           If you need a larger total stack size, use --main-stacksize to
           specify it. Only set it as high as you need, since reserving far more
           space than you need (that is, hundreds of megabytes more than you
           need) constrains Valgrind's memory allocators and may reduce the
           total amount of memory that Valgrind can use. This is only really of
           significance on 32-bit machines.

           On Linux, you may request a stack of size up to 2GB. Valgrind will
           stop with a diagnostic message if the stack cannot be allocated.

           --main-stacksize only affects the stack size for the program's
           initial thread. It has no bearing on the size of thread stacks, as
           Valgrind does not allocate those.

           You may need to use both --main-stacksize and --max-stackframe
           together. It is important to understand that --main-stacksize sets
           the maximum total stack size, whilst --max-stackframe specifies the
           largest size of any one stack frame. You will have to work out the
           --main-stacksize value for yourself (usually, if your applications
           segfaults). But Valgrind will tell you the needed --max-stackframe
           size, if necessary.

           As discussed further in the description of --max-stackframe, a
           requirement for a large stack is a sign of potential portability
           problems. You are best advised to place all large data in
           heap-allocated memory.

       --max-threads=<number> [default: 500]
           By default, Valgrind can handle to up to 500 threads. Occasionally,
           that number is too small. Use this option to provide a different
           limit. E.g.  --max-threads=3000.

       For tools that use their own version of malloc (e.g. Memcheck, Massif,
       Helgrind, DRD), the following options apply.

       --alignment=<number> [default: 8 or 16, depending on the platform]
           By default Valgrind's malloc, realloc, etc, return a block whose
           starting address is 8-byte aligned or 16-byte aligned (the value
           depends on the platform and matches the platform default). This
           option allows you to specify a different alignment. The supplied
           value must be greater than or equal to the default, less than or
           equal to 4096, and must be a power of two.

       --redzone-size=<number> [default: depends on the tool]
           Valgrind's malloc, realloc, etc, add padding blocks before and after
           each heap block allocated by the program being run. Such padding
           blocks are called redzones. The default value for the redzone size
           depends on the tool. For example, Memcheck adds and protects a
           minimum of 16 bytes before and after each block allocated by the
           client. This allows it to detect block underruns or overruns of up to
           16 bytes.

           Increasing the redzone size makes it possible to detect overruns of
           larger distances, but increases the amount of memory used by
           Valgrind. Decreasing the redzone size will reduce the memory needed
           by Valgrind but also reduces the chances of detecting over/underruns,
           so is not recommended.

       --xtree-memory=none|allocs|full [none]
           Tools replacing Valgrind's malloc, realloc, etc, can optionally
           produce an execution tree detailing which piece of code is
           responsible for heap memory usage. See Execution Trees for a detailed
           explanation about execution trees.

           When set to none, no memory execution tree is produced.

           When set to allocs, the memory execution tree gives the current
           number of allocated bytes and the current number of allocated blocks.

           When set to full, the memory execution tree gives 6 different
           measurements : the current number of allocated bytes and blocks (same
           values as for allocs), the total number of allocated bytes and
           blocks, the total number of freed bytes and blocks.

           Note that the overhead in cpu and memory to produce an xtree depends
           on the tool. The overhead in cpu is small for the value allocs, as
           the information needed to produce this report is maintained in any
           case by the tool. For massif and helgrind, specifying full implies to
           capture a stack trace for each free operation, while normally these
           tools only capture an allocation stack trace. For Memcheck, the cpu
           overhead for the value full is small, as this can only be used in
           combination with --keep-stacktraces=alloc-and-free or
           --keep-stacktraces=alloc-then-free, which already records a stack
           trace for each free operation. The memory overhead varies between 5
           and 10 words per unique stacktrace in the xtree, plus the memory
           needed to record the stack trace for the free operations, if needed
           specifically for the xtree.

       --xtree-memory-file=<filename> [default: xtmemory.kcg.%p]
           Specifies that Valgrind should produce the xtree memory report in the
           specified file. Any %p or %q sequences appearing in the filename are
           expanded in exactly the same way as they are for --log-file. See the
           description of --log-file for details.

           If the filename contains the extension .ms, then the produced file
           format will be a massif output file format. If the filename contains
           the extension .kcg or no extension is provided or recognised, then
           the produced file format will be a callgrind output format.

           See Execution Trees for a detailed explanation about execution trees

       These options apply to all tools, as they affect certain obscure workings
       of the Valgrind core. Most people won't need to use them.

       --smc-check=<none|stack|all|all-non-file> [default: all-non-file for
       x86/amd64/s390x, stack for other archs]
           This option controls Valgrind's detection of self-modifying code. If
           no checking is done, when a program executes some code, then
           overwrites it with new code, and executes the new code, Valgrind will
           continue to execute the translations it made for the old code. This
           will likely lead to incorrect behaviour and/or crashes.

           For "modern" architectures -- anything that's not x86, amd64 or s390x
           -- the default is stack. This is because a correct program must take
           explicit action to reestablish D-I cache coherence following code
           modification. Valgrind observes and honours such actions, with the
           result that self-modifying code is transparently handled with zero
           extra cost.

           For x86, amd64 and s390x, the program is not required to notify the
           hardware of required D-I coherence syncing. Hence the default is
           all-non-file, which covers the normal case of generating code into an
           anonymous (non-file-backed) mmap'd area.

           The meanings of the four available settings are as follows. No
           detection (none), detect self-modifying code on the stack (which is
           used by GCC to implement nested functions) (stack), detect
           self-modifying code everywhere (all), and detect self-modifying code
           everywhere except in file-backed mappings (all-non-file).

           Running with all will slow Valgrind down noticeably. Running with
           none will rarely speed things up, since very little code gets
           dynamically generated in most programs. The
           VALGRIND_DISCARD_TRANSLATIONS client request is an alternative to
           --smc-check=all and --smc-check=all-non-file that requires more
           programmer effort but allows Valgrind to run your program faster, by
           telling it precisely when translations need to be re-made.

           --smc-check=all-non-file provides a cheaper but more limited version
           of --smc-check=all. It adds checks to any translations that do not
           originate from file-backed memory mappings. Typical applications that
           generate code, for example JITs in web browsers, generate code into
           anonymous mmaped areas, whereas the "fixed" code of the browser
           always lives in file-backed mappings.  --smc-check=all-non-file takes
           advantage of this observation, limiting the overhead of checking to
           code which is likely to be JIT generated.

       --read-inline-info=<yes|no> [default: see below]
           When enabled, Valgrind will read information about inlined function
           calls from DWARF3 debug info. This slows Valgrind startup and makes
           it use more memory (typically for each inlined piece of code, 6 words
           and space for the function name), but it results in more descriptive
           stacktraces. Currently, this functionality is enabled by default only
           for Linux, Android and Solaris targets and only for the tools
           Memcheck, Massif, Helgrind and DRD. Here is an example of some
           stacktraces with --read-inline-info=no:

               ==15380== Conditional jump or move depends on uninitialised value(s)
               ==15380==    at 0x80484EA: main (inlinfo.c:6)
               ==15380== Conditional jump or move depends on uninitialised value(s)
               ==15380==    at 0x8048550: fun_noninline (inlinfo.c:6)
               ==15380==    by 0x804850E: main (inlinfo.c:34)
               ==15380== Conditional jump or move depends on uninitialised value(s)
               ==15380==    at 0x8048520: main (inlinfo.c:6)

           And here are the same errors with --read-inline-info=yes:

               ==15377== Conditional jump or move depends on uninitialised value(s)
               ==15377==    at 0x80484EA: fun_d (inlinfo.c:6)
               ==15377==    by 0x80484EA: fun_c (inlinfo.c:14)
               ==15377==    by 0x80484EA: fun_b (inlinfo.c:20)
               ==15377==    by 0x80484EA: fun_a (inlinfo.c:26)
               ==15377==    by 0x80484EA: main (inlinfo.c:33)
               ==15377== Conditional jump or move depends on uninitialised value(s)
               ==15377==    at 0x8048550: fun_d (inlinfo.c:6)
               ==15377==    by 0x8048550: fun_noninline (inlinfo.c:41)
               ==15377==    by 0x804850E: main (inlinfo.c:34)
               ==15377== Conditional jump or move depends on uninitialised value(s)
               ==15377==    at 0x8048520: fun_d (inlinfo.c:6)
               ==15377==    by 0x8048520: main (inlinfo.c:35)

       --read-var-info=<yes|no> [default: no]
           When enabled, Valgrind will read information about variable types and
           locations from DWARF3 debug info. This slows Valgrind startup
           significantly and makes it use significantly more memory, but for the
           tools that can take advantage of it (Memcheck, Helgrind, DRD) it can
           result in more precise error messages. For example, here are some
           standard errors issued by Memcheck:

               ==15363== Uninitialised byte(s) found during client check request
               ==15363==    at 0x80484A9: croak (varinfo1.c:28)
               ==15363==    by 0x8048544: main (varinfo1.c:55)
               ==15363==  Address 0x80497f7 is 7 bytes inside data symbol "global_i2"
               ==15363== Uninitialised byte(s) found during client check request
               ==15363==    at 0x80484A9: croak (varinfo1.c:28)
               ==15363==    by 0x8048550: main (varinfo1.c:56)
               ==15363==  Address 0xbea0d0cc is on thread 1's stack
               ==15363==  in frame #1, created by main (varinfo1.c:45)

           And here are the same errors with --read-var-info=yes:

               ==15370== Uninitialised byte(s) found during client check request
               ==15370==    at 0x80484A9: croak (varinfo1.c:28)
               ==15370==    by 0x8048544: main (varinfo1.c:55)
               ==15370==  Location 0x80497f7 is 0 bytes inside global_i2[7],
               ==15370==  a global variable declared at varinfo1.c:41
               ==15370== Uninitialised byte(s) found during client check request
               ==15370==    at 0x80484A9: croak (varinfo1.c:28)
               ==15370==    by 0x8048550: main (varinfo1.c:56)
               ==15370==  Location 0xbeb4a0cc is 0 bytes inside local var "local"
               ==15370==  declared at varinfo1.c:46, in frame #1 of thread 1

       --vgdb-poll=<number> [default: 5000]
           As part of its main loop, the Valgrind scheduler will poll to check
           if some activity (such as an external command or some input from a
           gdb) has to be handled by gdbserver. This activity poll will be done
           after having run the given number of basic blocks (or slightly more
           than the given number of basic blocks). This poll is quite cheap so
           the default value is set relatively low. You might further decrease
           this value if vgdb cannot use ptrace system call to interrupt
           Valgrind if all threads are (most of the time) blocked in a system

       --vgdb-shadow-registers=no|yes [default: no]
           When activated, gdbserver will expose the Valgrind shadow registers
           to GDB. With this, the value of the Valgrind shadow registers can be
           examined or changed using GDB. Exposing shadow registers only works
           with GDB version 7.1 or later.

       --vgdb-prefix=<prefix> [default: /tmp/vgdb-pipe]
           To communicate with gdb/vgdb, the Valgrind gdbserver creates 3 files
           (2 named FIFOs and a mmap shared memory file). The prefix option
           controls the directory and prefix for the creation of these files.

       --run-libc-freeres=<yes|no> [default: yes]
           This option is only relevant when running Valgrind on Linux.

           The GNU C library (, which is used by all programs, may
           allocate memory for its own uses. Usually it doesn't bother to free
           that memory when the program ends—there would be no point, since the
           Linux kernel reclaims all process resources when a process exits
           anyway, so it would just slow things down.

           The glibc authors realised that this behaviour causes leak checkers,
           such as Valgrind, to falsely report leaks in glibc, when a leak check
           is done at exit. In order to avoid this, they provided a routine
           called __libc_freeres specifically to make glibc release all memory
           it has allocated. Memcheck therefore tries to run __libc_freeres at

           Unfortunately, in some very old versions of glibc, __libc_freeres is
           sufficiently buggy to cause segmentation faults. This was
           particularly noticeable on Red Hat 7.1. So this option is provided in
           order to inhibit the run of __libc_freeres. If your program seems to
           run fine on Valgrind, but segfaults at exit, you may find that
           --run-libc-freeres=no fixes that, although at the cost of possibly
           falsely reporting space leaks in

       --run-cxx-freeres=<yes|no> [default: yes]
           This option is only relevant when running Valgrind on Linux or
           Solaris C++ programs.

           The GNU Standard C++ library (, which is used by all C++
           programs compiled with g++, may allocate memory for its own uses.
           Usually it doesn't bother to free that memory when the program ends—
           there would be no point, since the kernel reclaims all process
           resources when a process exits anyway, so it would just slow things

           The gcc authors realised that this behaviour causes leak checkers,
           such as Valgrind, to falsely report leaks in libstdc++, when a leak
           check is done at exit. In order to avoid this, they provided a
           routine called __gnu_cxx::__freeres specifically to make libstdc++
           release all memory it has allocated. Memcheck therefore tries to run
           __gnu_cxx::__freeres at exit.

           For the sake of flexibility and unforeseen problems with
           __gnu_cxx::__freeres, option --run-cxx-freeres=no exists, although at
           the cost of possibly falsely reporting space leaks in

           Pass miscellaneous hints to Valgrind which slightly modify the
           simulated behaviour in nonstandard or dangerous ways, possibly to
           help the simulation of strange features. By default no hints are
           enabled. Use with caution! Currently known hints are:

           •   lax-ioctls: Be very lax about ioctl handling; the only assumption
               is that the size is correct. Doesn't require the full buffer to
               be initialised when writing. Without this, using some device
               drivers with a large number of strange ioctl commands becomes
               very tiresome.

           •   fuse-compatible: Enable special handling for certain system calls
               that may block in a FUSE file-system. This may be necessary when
               running Valgrind on a multi-threaded program that uses one thread
               to manage a FUSE file-system and another thread to access that

           •   enable-outer: Enable some special magic needed when the program
               being run is itself Valgrind.

           •   no-inner-prefix: Disable printing a prefix > in front of each
               stdout or stderr output line in an inner Valgrind being run by an
               outer Valgrind. This is useful when running Valgrind regression
               tests in an outer/inner setup. Note that the prefix > will always
               be printed in front of the inner debug logging lines.

           •   no-nptl-pthread-stackcache: This hint is only relevant when
               running Valgrind on Linux; it is ignored on Solaris and Mac OS X.

               The GNU glibc pthread library (, which is used by
               pthread programs, maintains a cache of pthread stacks. When a
               pthread terminates, the memory used for the pthread stack and
               some thread local storage related data structure are not always
               directly released. This memory is kept in a cache (up to a
               certain size), and is re-used if a new thread is started.

               This cache causes the helgrind tool to report some false positive
               race condition errors on this cached memory, as helgrind does not
               understand the internal glibc cache synchronisation primitives.
               So, when using helgrind, disabling the cache helps to avoid false
               positive race conditions, in particular when using thread local
               storage variables (e.g. variables using the __thread qualifier).

               When using the memcheck tool, disabling the cache ensures the
               memory used by glibc to handle __thread variables is directly
               released when a thread terminates.

               Note: Valgrind disables the cache using some internal knowledge
               of the glibc stack cache implementation and by examining the
               debug information of the pthread library. This technique is thus
               somewhat fragile and might not work for all glibc versions. This
               has been successfully tested with various glibc versions (e.g.
               2.11, 2.16, 2.18) on various platforms.

           •   lax-doors: (Solaris only) Be very lax about door syscall handling
               over unrecognised door file descriptors. Does not require that
               full buffer is initialised when writing. Without this, programs
               using libdoor(3LIB) functionality with completely proprietary
               semantics may report large number of false positives.

           •   fallback-llsc: (MIPS and ARM64 only): Enables an alternative
               implementation of Load-Linked (LL) and Store-Conditional (SC)
               instructions. The standard implementation gives more correct
               behaviour, but can cause indefinite looping on certain processor
               implementations that are intolerant of extra memory references
               between LL and SC. So far this is known only to happen on Cavium
               3 cores. You should not need to use this flag, since the relevant
               cores are detected at startup and the alternative implementation
               is automatically enabled if necessary. There is no equivalent
               anti-flag: you cannot force-disable the alternative
               implementation, if it is automatically enabled. The underlying
               problem exists because the "standard" implementation of LL and SC
               is done by copying through LL and SC instructions into the
               instrumented code. However, tools may insert extra
               instrumentation memory references in between the LL and SC
               instructions. These memory references are not present in the
               original uninstrumented code, and their presence in the
               instrumented code can cause the SC instructions to persistently
               fail, leading to indefinite looping in LL-SC blocks. The
               alternative implementation gives correct behaviour of LL and SC
               instructions between threads in a process, up to and including
               the ABA scenario. It also gives correct behaviour between a
               Valgrinded thread and a non-Valgrinded thread running in a
               different process, that communicate via shared memory, but only
               up to and including correct CAS behaviour -- in this case the ABA
               scenario may not be correctly handled.

       --fair-sched=<no|yes|try> [default: no]
           The --fair-sched option controls the locking mechanism used by
           Valgrind to serialise thread execution. The locking mechanism
           controls the way the threads are scheduled, and different settings
           give different trade-offs between fairness and performance. For more
           details about the Valgrind thread serialisation scheme and its impact
           on performance and thread scheduling, see Scheduling and Multi-Thread

           •   The value --fair-sched=yes activates a fair scheduler. In short,
               if multiple threads are ready to run, the threads will be
               scheduled in a round robin fashion. This mechanism is not
               available on all platforms or Linux versions. If not available,
               using --fair-sched=yes will cause Valgrind to terminate with an

               You may find this setting improves overall responsiveness if you
               are running an interactive multithreaded program, for example a
               web browser, on Valgrind.

           •   The value --fair-sched=try activates fair scheduling if available
               on the platform. Otherwise, it will automatically fall back to

           •   The value --fair-sched=no activates a scheduler which does not
               guarantee fairness between threads ready to run, but which in
               general gives the highest performance.

           Handle system calls and ioctls arising from minor variants of the
           default kernel for this platform. This is useful for running on
           hacked kernels or with kernel modules which support nonstandard
           ioctls, for example. Use with caution. If you don't understand what
           this option does then you almost certainly don't need it. Currently
           known variants are:

           •   bproc: support the sys_broc system call on x86. This is for
               running on BProc, which is a minor variant of standard Linux
               which is sometimes used for building clusters.

           •   android-no-hw-tls: some versions of the Android emulator for ARM
               do not provide a hardware TLS (thread-local state) register, and
               Valgrind crashes at startup. Use this variant to select software
               support for TLS.

           •   android-gpu-sgx5xx: use this to support handling of proprietary
               ioctls for the PowerVR SGX 5XX series of GPUs on Android devices.
               Failure to select this does not cause stability problems, but may
               cause Memcheck to report false errors after the program performs
               GPU-specific ioctls.

           •   android-gpu-adreno3xx: similarly, use this to support handling of
               proprietary ioctls for the Qualcomm Adreno 3XX series of GPUs on
               Android devices.

       --merge-recursive-frames=<number> [default: 0]
           Some recursive algorithms, for example balanced binary tree
           implementations, create many different stack traces, each containing
           cycles of calls. A cycle is defined as two identical program counter
           values separated by zero or more other program counter values.
           Valgrind may then use a lot of memory to store all these stack
           traces. This is a poor use of memory considering that such stack
           traces contain repeated uninteresting recursive calls instead of more
           interesting information such as the function that has initiated the
           recursive call.

           The option --merge-recursive-frames=<number> instructs Valgrind to
           detect and merge recursive call cycles having a size of up to
           <number> frames. When such a cycle is detected, Valgrind records the
           cycle in the stack trace as a unique program counter.

           The value 0 (the default) causes no recursive call merging. A value
           of 1 will cause stack traces of simple recursive algorithms (for
           example, a factorial implementation) to be collapsed. A value of 2
           will usually be needed to collapse stack traces produced by recursive
           algorithms such as binary trees, quick sort, etc. Higher values might
           be needed for more complex recursive algorithms.

           Note: recursive calls are detected by analysis of program counter
           values. They are not detected by looking at function names.

       --num-transtab-sectors=<number> [default: 6 for Android platforms, 16 for
       all others]
           Valgrind translates and instruments your program's machine code in
           small fragments (basic blocks). The translations are stored in a
           translation cache that is divided into a number of sections
           (sectors). If the cache is full, the sector containing the oldest
           translations is emptied and reused. If these old translations are
           needed again, Valgrind must re-translate and re-instrument the
           corresponding machine code, which is expensive. If the "executed
           instructions" working set of a program is big, increasing the number
           of sectors may improve performance by reducing the number of
           re-translations needed. Sectors are allocated on demand. Once
           allocated, a sector can never be freed, and occupies considerable
           space, depending on the tool and the value of
           --avg-transtab-entry-size (about 40 MB per sector for Memcheck). Use
           the option --stats=yes to obtain precise information about the memory
           used by a sector and the allocation and recycling of sectors.

       --avg-transtab-entry-size=<number> [default: 0, meaning use tool provided
           Average size of translated basic block. This average size is used to
           dimension the size of a sector. Each tool provides a default value to
           be used. If this default value is too small, the translation sectors
           will become full too quickly. If this default value is too big, a
           significant part of the translation sector memory will be unused.
           Note that the average size of a basic block translation depends on
           the tool, and might depend on tool options. For example, the memcheck
           option --track-origins=yes increases the size of the basic block
           translations. Use --avg-transtab-entry-size to tune the size of the
           sectors, either to gain memory or to avoid too many retranslations.

       --aspace-minaddr=<address> [default: depends on the platform]
           To avoid potential conflicts with some system libraries, Valgrind
           does not use the address space below --aspace-minaddr value, keeping
           it reserved in case a library specifically requests memory in this
           region. So, some "pessimistic" value is guessed by Valgrind depending
           on the platform. On linux, by default, Valgrind avoids using the
           first 64MB even if typically there is no conflict in this complete
           zone. You can use the option --aspace-minaddr to have your memory
           hungry application benefitting from more of this lower memory. On the
           other hand, if you encounter a conflict, increasing aspace-minaddr
           value might solve it. Conflicts will typically manifest themselves
           with mmap failures in the low range of the address space. The
           provided address must be page aligned and must be equal or bigger to
           0x1000 (4KB). To find the default value on your platform, do
           something such as valgrind -d -d date 2>&1 | grep -i minaddr. Values
           lower than 0x10000 (64KB) are known to create problems on some

       --valgrind-stacksize=<number> [default: 1MB]
           For each thread, Valgrind needs its own 'private' stack. The default
           size for these stacks is largely dimensioned, and so should be
           sufficient in most cases. In case the size is too small, Valgrind
           will segfault. Before segfaulting, a warning might be produced by
           Valgrind when approaching the limit.

           Use the option --valgrind-stacksize if such an (unlikely) warning is
           produced, or Valgrind dies due to a segmentation violation. Such
           segmentation violations have been seen when demangling huge C++

           If your application uses many threads and needs a lot of memory, you
           can gain some memory by reducing the size of these Valgrind stacks
           using the option --valgrind-stacksize.

       --show-emwarns=<yes|no> [default: no]
           When enabled, Valgrind will emit warnings about its CPU emulation in
           certain cases. These are usually not interesting.

           When a shared object whose soname matches sonamepatt is loaded into
           the process, examine all the text symbols it exports. If none of
           those match fnnamepatt, print an error message and abandon the run.
           This makes it possible to ensure that the run does not continue
           unless a given shared object contains a particular function name.

           Both sonamepatt and fnnamepatt can be written using the usual ?  and
           * wildcards. For example: ":**:foo?bar". You may use
           characters other than a colon to separate the two patterns. It is
           only important that the first character and the separator character
           are the same. For example, the above example could also be written
           "Q**Qfoo?bar". Multiple
            --require-text-symbol flags are allowed, in which case shared
           objects that are loaded into the process will be checked against all
           of them.

           The purpose of this is to support reliable usage of marked-up
           libraries. For example, suppose we have a version of GCC's
           which has been marked up with annotations to support Helgrind. It is
           only too easy and confusing to load the wrong, un-annotated
  into the application. So the idea is: add a text symbol in
           the marked-up library, for example annotated_for_helgrind_3_6, and
           then give the flag
           --require-text-symbol=:*libgomp*so*:annotated_for_helgrind_3_6 so
           that when is loaded, Valgrind scans its symbol table, and
           if the symbol isn't present the run is aborted, rather than
           continuing silently with the un-marked-up library. Note that you
           should put the entire flag in quotes to stop shells expanding up the
           * and ?  wildcards.

           When a shared library is loaded, Valgrind checks for functions in the
           library that must be replaced or wrapped. For example, Memcheck
           replaces some string and memory functions (strchr, strlen, strcpy,
           memchr, memcpy, memmove, etc.) with its own versions. Such
           replacements are normally done only in shared libraries whose soname
           matches a predefined soname pattern (e.g.* on linux). By
           default, no replacement is done for a statically linked binary or for
           alternative libraries, except for the allocation functions (malloc,
           free, calloc, memalign, realloc, operator new, operator delete, etc.)
           Such allocation functions are intercepted by default in any shared
           library or in the executable if they are exported as global symbols.
           This means that if a replacement allocation library such as tcmalloc
           is found, its functions are also intercepted by default. In some
           cases, the replacements allow --soname-synonyms to specify one
           additional synonym pattern, giving flexibility in the replacement. Or
           to prevent interception of all public allocation symbols.

           Currently, this flexibility is only allowed for the malloc related
           functions, using the synonym somalloc. This synonym is usable for all
           tools doing standard replacement of malloc related functions (e.g.
           memcheck, helgrind, drd, massif, dhat).

           •   Alternate malloc library: to replace the malloc related functions
               in a specific alternate library with soname (and
               not in any others), give the option
      A pattern can be used
               to match multiple libraries sonames. For example,
               --soname-synonyms=somalloc=*tcmalloc* will match the soname of
               all variants of the tcmalloc library (native, debug, profiled,
               ... tcmalloc variants).

               Note: the soname of a elf shared library can be retrieved using
               the readelf utility.

           •   Replacements in a statically linked library are done by using the
               NONE pattern. For example, if you link with libtcmalloc.a, and
               only want to intercept the malloc related functions in the
               executable (and standard libraries) themselves, but not any other
               shared libraries, you can give the option
               --soname-synonyms=somalloc=NONE. Note that a NONE pattern will
               match the main executable and any shared library having no

           •   To run a "default" Firefox build for Linux, in which JEMalloc is
               linked in to the main executable, use

           •   To only intercept allocation symbols in the default system
               libraries, but not in any other shared library or the executable
               defining public malloc or operator new related functions use a
               non-existing library name like
               --soname-synonyms=somalloc=nouserintercepts (where
               nouserintercepts can be any non-existing library name).

           •   Shared library of the dynamic (runtime) linker is excluded from
               searching for global public symbols, such as those for the malloc
               related functions (identified by somalloc synonym).

       --progress-interval=<number> [default: 0, meaning 'disabled']
           This is an enhancement to Valgrind's debugging output. It is unlikely
           to be of interest to end users.

           When number is set to a non-zero value, Valgrind will print a
           one-line progress summary every number seconds. Valid settings for
           number are between 0 and 3600 inclusive. Here's some example output
           with number set to 10:

               PROGRESS: U 110s, W 113s, 97.3% CPU, EvC 414.79M, TIn 616.7k, TOut 0.5k, #thr 67
               PROGRESS: U 120s, W 124s, 96.8% CPU, EvC 505.27M, TIn 636.6k, TOut 3.0k, #thr 64
               PROGRESS: U 130s, W 134s, 97.0% CPU, EvC 574.90M, TIn 657.5k, TOut 3.0k, #thr 63

           Each line shows:

           •   U: total user time

           •   W: total wallclock time

           •   CPU: overall average cpu use

           •   EvC: number of event checks. An event check is a backwards branch
               in the simulated program, so this is a measure of forward
               progress of the program

           •   TIn: number of code blocks instrumented by the JIT

           •   TOut: number of instrumented code blocks that have been thrown

           •   #thr: number of threads in the program

           From the progress of these, it is possible to observe:

           •   when the program is compute bound (TIn rises slowly, EvC rises

           •   when the program is in a spinloop (TIn/TOut fixed, EvC rises

           •   when the program is JIT-bound (TIn rises rapidly)

           •   when the program is rapidly discarding code (TOut rises rapidly)

           •   when the program is about to achieve some expected state (EvC
               arrives at some value you expect)

           •   when the program is idling (U rises more slowly than W)

       There are also some options for debugging Valgrind itself. You shouldn't
       need to use them in the normal run of things. If you wish to see the
       list, use the --help-debug option.

       --leak-check=<no|summary|yes|full> [default: summary]
           When enabled, search for memory leaks when the client program
           finishes. If set to summary, it says how many leaks occurred. If set
           to full or yes, each individual leak will be shown in detail and/or
           counted as an error, as specified by the options --show-leak-kinds
           and --errors-for-leak-kinds.

           If --xml=yes is given, memcheck will automatically use the value
           --leak-check=full. You can use --show-leak-kinds=none to reduce the
           size of the xml output if you are not interested in the leak results.

       --leak-resolution=<low|med|high> [default: high]
           When doing leak checking, determines how willing Memcheck is to
           consider different backtraces to be the same for the purposes of
           merging multiple leaks into a single leak report. When set to low,
           only the first two entries need match. When med, four entries have to
           match. When high, all entries need to match.

           For hardcore leak debugging, you probably want to use
           --leak-resolution=high together with --num-callers=40 or some such
           large number.

           Note that the --leak-resolution setting does not affect Memcheck's
           ability to find leaks. It only changes how the results are presented.

       --show-leak-kinds=<set> [default: definite,possible]
           Specifies the leak kinds to show in a full leak search, in one of the
           following ways:

           •   a comma separated list of one or more of definite indirect
               possible reachable.

           •   all to specify the complete set (all leak kinds). It is
               equivalent to

           •   none for the empty set.

       --errors-for-leak-kinds=<set> [default: definite,possible]
           Specifies the leak kinds to count as errors in a full leak search.
           The <set> is specified similarly to --show-leak-kinds

       --leak-check-heuristics=<set> [default: all]
           Specifies the set of leak check heuristics to be used during leak
           searches. The heuristics control which interior pointers to a block
           cause it to be considered as reachable. The heuristic set is
           specified in one of the following ways:

           •   a comma separated list of one or more of stdstring length64
               newarray multipleinheritance.

           •   all to activate the complete set of heuristics. It is equivalent

           •   none for the empty set.

           Note that these heuristics are dependent on the layout of the objects
           produced by the C++ compiler. They have been tested with some gcc
           versions (e.g. 4.4 and 4.7). They might not work properly with other
           C++ compilers.

       --show-reachable=<yes|no> , --show-possibly-lost=<yes|no>
           These options provide an alternative way to specify the leak kinds to

           •   --show-reachable=no --show-possibly-lost=yes is equivalent to

           •   --show-reachable=no --show-possibly-lost=no is equivalent to

           •   --show-reachable=yes is equivalent to --show-leak-kinds=all.

           Note that --show-possibly-lost=no has no effect if
           --show-reachable=yes is specified.

       --xtree-leak=<no|yes> [no]
           If set to yes, the results for the leak search done at exit will be
           output in a 'Callgrind Format' execution tree file. Note that this
           automatically sets the options --leak-check=full and
           --show-leak-kinds=all, to allow xtree visualisation tools such as
           kcachegrind to select what kind to leak to visualise. The produced
           file will contain the following events:

           •   RB : Reachable Bytes

           •   PB : Possibly lost Bytes

           •   IB : Indirectly lost Bytes

           •   DB : Definitely lost Bytes (direct plus indirect)

           •   DIB : Definitely Indirectly lost Bytes (subset of DB)

           •   RBk : reachable Blocks

           •   PBk : Possibly lost Blocks

           •   IBk : Indirectly lost Blocks

           •   DBk : Definitely lost Blocks

           The increase or decrease for all events above will also be output in
           the file to provide the delta (increase or decrease) between 2
           successive leak searches. For example, iRB is the increase of the RB
           event, dPBk is the decrease of PBk event. The values for the increase
           and decrease events will be zero for the first leak search done.

           See Execution Trees for a detailed explanation about execution trees.

       --xtree-leak-file=<filename> [default: xtleak.kcg.%p]
           Specifies that Valgrind should produce the xtree leak report in the
           specified file. Any %p, %q or %n sequences appearing in the filename
           are expanded in exactly the same way as they are for --log-file. See
           the description of --log-file for details.

           See Execution Trees for a detailed explanation about execution trees

       --undef-value-errors=<yes|no> [default: yes]
           Controls whether Memcheck reports uses of undefined value errors. Set
           this to no if you don't want to see undefined value errors. It also
           has the side effect of speeding up Memcheck somewhat. AddrCheck
           (removed in Valgrind 3.1.0) functioned like Memcheck with

       --track-origins=<yes|no> [default: no]
           Controls whether Memcheck tracks the origin of uninitialised values.
           By default, it does not, which means that although it can tell you
           that an uninitialised value is being used in a dangerous way, it
           cannot tell you where the uninitialised value came from. This often
           makes it difficult to track down the root problem.

           When set to yes, Memcheck keeps track of the origins of all
           uninitialised values. Then, when an uninitialised value error is
           reported, Memcheck will try to show the origin of the value. An
           origin can be one of the following four places: a heap block, a stack
           allocation, a client request, or miscellaneous other sources (eg, a
           call to brk).

           For uninitialised values originating from a heap block, Memcheck
           shows where the block was allocated. For uninitialised values
           originating from a stack allocation, Memcheck can tell you which
           function allocated the value, but no more than that -- typically it
           shows you the source location of the opening brace of the function.
           So you should carefully check that all of the function's local
           variables are initialised properly.

           Performance overhead: origin tracking is expensive. It halves
           Memcheck's speed and increases memory use by a minimum of 100MB, and
           possibly more. Nevertheless it can drastically reduce the effort
           required to identify the root cause of uninitialised value errors,
           and so is often a programmer productivity win, despite running more

           Accuracy: Memcheck tracks origins quite accurately. To avoid very
           large space and time overheads, some approximations are made. It is
           possible, although unlikely, that Memcheck will report an incorrect
           origin, or not be able to identify any origin.

           Note that the combination --track-origins=yes and
           --undef-value-errors=no is nonsensical. Memcheck checks for and
           rejects this combination at startup.

       --partial-loads-ok=<yes|no> [default: yes]
           Controls how Memcheck handles 32-, 64-, 128- and 256-bit naturally
           aligned loads from addresses for which some bytes are addressable and
           others are not. When yes, such loads do not produce an address error.
           Instead, loaded bytes originating from illegal addresses are marked
           as uninitialised, and those corresponding to legal addresses are
           handled in the normal way.

           When no, loads from partially invalid addresses are treated the same
           as loads from completely invalid addresses: an illegal-address error
           is issued, and the resulting bytes are marked as initialised.

           Note that code that behaves in this way is in violation of the ISO
           C/C++ standards, and should be considered broken. If at all possible,
           such code should be fixed.

       --expensive-definedness-checks=<no|auto|yes> [default: auto]
           Controls whether Memcheck should employ more precise but also more
           expensive (time consuming) instrumentation when checking the
           definedness of certain values. In particular, this affects the
           instrumentation of integer adds, subtracts and equality comparisons.

           Selecting --expensive-definedness-checks=yes causes Memcheck to use
           the most accurate analysis possible. This minimises false error rates
           but can cause up to 30% performance degradation.

           Selecting --expensive-definedness-checks=no causes Memcheck to use
           the cheapest instrumentation possible. This maximises performance but
           will normally give an unusably high false error rate.

           The default setting, --expensive-definedness-checks=auto, is strongly
           recommended. This causes Memcheck to use the minimum of expensive
           instrumentation needed to achieve the same false error rate as
           --expensive-definedness-checks=yes. It also enables an
           instrumentation-time analysis pass which aims to further reduce the
           costs of accurate instrumentation. Overall, the performance loss is
           generally around 5% relative to --expensive-definedness-checks=no,
           although this is strongly workload dependent. Note that the exact
           instrumentation settings in this mode are architecture dependent.

       [default: alloc-and-free]
           Controls which stack trace(s) to keep for malloc'd and/or free'd

           With alloc-then-free, a stack trace is recorded at allocation time,
           and is associated with the block. When the block is freed, a second
           stack trace is recorded, and this replaces the allocation stack
           trace. As a result, any "use after free" errors relating to this
           block can only show a stack trace for where the block was freed.

           With alloc-and-free, both allocation and the deallocation stack
           traces for the block are stored. Hence a "use after free" error will
           show both, which may make the error easier to diagnose. Compared to
           alloc-then-free, this setting slightly increases Valgrind's memory
           use as the block contains two references instead of one.

           With alloc, only the allocation stack trace is recorded (and
           reported). With free, only the deallocation stack trace is recorded
           (and reported). These values somewhat decrease Valgrind's memory and
           cpu usage. They can be useful depending on the error types you are
           searching for and the level of detail you need to analyse them. For
           example, if you are only interested in memory leak errors, it is
           sufficient to record the allocation stack traces.

           With none, no stack traces are recorded for malloc and free
           operations. If your program allocates a lot of blocks and/or
           allocates/frees from many different stack traces, this can
           significantly decrease cpu and/or memory required. Of course, few
           details will be reported for errors related to heap blocks.

           Note that once a stack trace is recorded, Valgrind keeps the stack
           trace in memory even if it is not referenced by any block. Some
           programs (for example, recursive algorithms) can generate a huge
           number of stack traces. If Valgrind uses too much memory in such
           circumstances, you can reduce the memory required with the options
           --keep-stacktraces and/or by using a smaller value for the option

           If you want to use --xtree-memory=full memory profiling (see
           Execution Trees), then you cannot specify --keep-stacktraces=free or

       --freelist-vol=<number> [default: 20000000]
           When the client program releases memory using free (in C) or delete
           (C++), that memory is not immediately made available for
           re-allocation. Instead, it is marked inaccessible and placed in a
           queue of freed blocks. The purpose is to defer as long as possible
           the point at which freed-up memory comes back into circulation. This
           increases the chance that Memcheck will be able to detect invalid
           accesses to blocks for some significant period of time after they
           have been freed.

           This option specifies the maximum total size, in bytes, of the blocks
           in the queue. The default value is twenty million bytes. Increasing
           this increases the total amount of memory used by Memcheck but may
           detect invalid uses of freed blocks which would otherwise go

       --freelist-big-blocks=<number> [default: 1000000]
           When making blocks from the queue of freed blocks available for
           re-allocation, Memcheck will in priority re-circulate the blocks with
           a size greater or equal to --freelist-big-blocks. This ensures that
           freeing big blocks (in particular freeing blocks bigger than
           --freelist-vol) does not immediately lead to a re-circulation of all
           (or a lot of) the small blocks in the free list. In other words, this
           option increases the likelihood to discover dangling pointers for the
           "small" blocks, even when big blocks are freed.

           Setting a value of 0 means that all the blocks are re-circulated in a
           FIFO order.

       --workaround-gcc296-bugs=<yes|no> [default: no]
           When enabled, assume that reads and writes some small distance below
           the stack pointer are due to bugs in GCC 2.96, and does not report
           them. The "small distance" is 256 bytes by default. Note that GCC
           2.96 is the default compiler on some ancient Linux distributions
           (RedHat 7.X) and so you may need to use this option. Do not use it if
           you do not have to, as it can cause real errors to be overlooked. A
           better alternative is to use a more recent GCC in which this bug is

           You may also need to use this option when working with GCC 3.X or 4.X
           on 32-bit PowerPC Linux. This is because GCC generates code which
           occasionally accesses below the stack pointer, particularly for
           floating-point to/from integer conversions. This is in violation of
           the 32-bit PowerPC ELF specification, which makes no provision for
           locations below the stack pointer to be accessible.

           This option is deprecated as of version 3.12 and may be removed from
           future versions. You should instead use --ignore-range-below-sp to
           specify the exact range of offsets below the stack pointer that
           should be ignored. A suitable equivalent is

           This is a more general replacement for the deprecated
           --workaround-gcc296-bugs option. When specified, it causes Memcheck
           not to report errors for accesses at the specified offsets below the
           stack pointer. The two offsets must be positive decimal numbers and
           -- somewhat counterintuitively -- the first one must be larger, in
           order to imply a non-wraparound address range to ignore. For example,
           to ignore 4 byte accesses at 8192 bytes below the stack pointer, use
           --ignore-range-below-sp=8192-8189. Only one range may be specified.

       --show-mismatched-frees=<yes|no> [default: yes]
           When enabled, Memcheck checks that heap blocks are deallocated using
           a function that matches the allocating function. That is, it expects
           free to be used to deallocate blocks allocated by malloc, delete for
           blocks allocated by new, and delete[] for blocks allocated by new[].
           If a mismatch is detected, an error is reported. This is in general
           important because in some environments, freeing with a non-matching
           function can cause crashes.

           There is however a scenario where such mismatches cannot be avoided.
           That is when the user provides implementations of new/new[] that call
           malloc and of delete/delete[] that call free, and these functions are
           asymmetrically inlined. For example, imagine that delete[] is inlined
           but new[] is not. The result is that Memcheck "sees" all delete[]
           calls as direct calls to free, even when the program source contains
           no mismatched calls.

           This causes a lot of confusing and irrelevant error reports.
           --show-mismatched-frees=no disables these checks. It is not generally
           advisable to disable them, though, because you may miss real errors
           as a result.

           Any ranges listed in this option (and multiple ranges can be
           specified, separated by commas) will be ignored by Memcheck's
           addressability checking.

           Fills blocks allocated by malloc, new, etc, but not by calloc, with
           the specified byte. This can be useful when trying to shake out
           obscure memory corruption problems. The allocated area is still
           regarded by Memcheck as undefined -- this option only affects its
           contents. Note that --malloc-fill does not affect a block of memory
           when it is used as argument to client requests VALGRIND_MEMPOOL_ALLOC

           Fills blocks freed by free, delete, etc, with the specified byte
           value. This can be useful when trying to shake out obscure memory
           corruption problems. The freed area is still regarded by Memcheck as
           not valid for access -- this option only affects its contents. Note
           that --free-fill does not affect a block of memory when it is used as
           argument to client requests VALGRIND_MEMPOOL_FREE or

       --I1=<size>,<associativity>,<line size>
           Specify the size, associativity and line size of the level 1
           instruction cache.

       --D1=<size>,<associativity>,<line size>
           Specify the size, associativity and line size of the level 1 data

       --LL=<size>,<associativity>,<line size>
           Specify the size, associativity and line size of the last-level

       --cache-sim=no|yes [yes]
           Enables or disables collection of cache access and miss counts.

       --branch-sim=no|yes [no]
           Enables or disables collection of branch instruction and
           misprediction counts. By default this is disabled as it slows
           Cachegrind down by approximately 25%. Note that you cannot specify
           --cache-sim=no and --branch-sim=no together, as that would leave
           Cachegrind with no information to collect.

           Write the profile data to file rather than to the default output
           file, cachegrind.out.<pid>. The %p and %q format specifiers can be
           used to embed the process ID and/or the contents of an environment
           variable in the name, as is the case for the core option --log-file.

           Write the profile data to file rather than to the default output
           file, callgrind.out.<pid>. The %p and %q format specifiers can be
           used to embed the process ID and/or the contents of an environment
           variable in the name, as is the case for the core option --log-file.
           When multiple dumps are made, the file name is modified further; see

       --dump-line=<no|yes> [default: yes]
           This specifies that event counting should be performed at source line
           granularity. This allows source annotation for sources which are
           compiled with debug information (-g).

       --dump-instr=<no|yes> [default: no]
           This specifies that event counting should be performed at
           per-instruction granularity. This allows for assembly code
           annotation. Currently the results can only be displayed by

       --compress-strings=<no|yes> [default: yes]
           This option influences the output format of the profile data. It
           specifies whether strings (file and function names) should be
           identified by numbers. This shrinks the file, but makes it more
           difficult for humans to read (which is not recommended in any case).

       --compress-pos=<no|yes> [default: yes]
           This option influences the output format of the profile data. It
           specifies whether numerical positions are always specified as
           absolute values or are allowed to be relative to previous numbers.
           This shrinks the file size.

       --combine-dumps=<no|yes> [default: no]
           When enabled, when multiple profile data parts are to be generated
           these parts are appended to the same output file. Not recommended.

       --dump-every-bb=<count> [default: 0, never]
           Dump profile data every count basic blocks. Whether a dump is needed
           is only checked when Valgrind's internal scheduler is run. Therefore,
           the minimum setting useful is about 100000. The count is a 64-bit
           value to make long dump periods possible.

           Dump when entering function.

           Zero all costs when entering function.

           Dump when leaving function.

       --instr-atstart=<yes|no> [default: yes]
           Specify if you want Callgrind to start simulation and profiling from
           the beginning of the program. When set to no, Callgrind will not be
           able to collect any information, including calls, but it will have at
           most a slowdown of around 4, which is the minimum Valgrind overhead.
           Instrumentation can be interactively enabled via callgrind_control -i

           Note that the resulting call graph will most probably not contain
           main, but will contain all the functions executed after
           instrumentation was enabled. Instrumentation can also be
           programmatically enabled/disabled. See the Callgrind include file
           callgrind.h for the macro you have to use in your source code.

           For cache simulation, results will be less accurate when switching on
           instrumentation later in the program run, as the simulator starts
           with an empty cache at that moment. Switch on event collection later
           to cope with this error.

       --collect-atstart=<yes|no> [default: yes]
           Specify whether event collection is enabled at beginning of the
           profile run.

           To only look at parts of your program, you have two possibilities:

            1. Zero event counters before entering the program part you want to
               profile, and dump the event counters to a file after leaving that
               program part.

            2. Switch on/off collection state as needed to only see event
               counters happening while inside of the program part you want to

           The second option can be used if the program part you want to profile
           is called many times. Option 1, i.e. creating a lot of dumps is not
           practical here.

           Collection state can be toggled at entry and exit of a given function
           with the option --toggle-collect. If you use this option, collection
           state should be disabled at the beginning. Note that the
           specification of --toggle-collect implicitly sets --collect-state=no.

           Collection state can be toggled also by inserting the client request
           CALLGRIND_TOGGLE_COLLECT ; at the needed code positions.

           Toggle collection on entry/exit of function.

       --collect-jumps=<no|yes> [default: no]
           This specifies whether information for (conditional) jumps should be
           collected. As above, callgrind_annotate currently is not able to show
           you the data. You have to use KCachegrind to get jump arrows in the
           annotated code.

       --collect-systime=<no|yes|msec|usec|nsec> [default: no]
           This specifies whether information for system call times should be

           The value no indicates to record no system call information.

           The other values indicate to record the number of system calls done
           (sysCount event) and the elapsed time (sysTime event) spent in system
           calls. The --collect-systime value gives the unit used for sysTime :
           milli seconds, micro seconds or nano seconds. With the value nsec,
           callgrind also records the cpu time spent during system calls

           The value yes is a synonym of msec. The value nsec is not supported
           on Darwin.

       --collect-bus=<no|yes> [default: no]
           This specifies whether the number of global bus events executed
           should be collected. The event type "Ge" is used for these events.

       --cache-sim=<yes|no> [default: no]
           Specify if you want to do full cache simulation. By default, only
           instruction read accesses will be counted ("Ir"). With cache
           simulation, further event counters are enabled: Cache misses on
           instruction reads ("I1mr"/"ILmr"), data read accesses ("Dr") and
           related cache misses ("D1mr"/"DLmr"), data write accesses ("Dw") and
           related cache misses ("D1mw"/"DLmw"). For more information, see
           Cachegrind: a cache and branch-prediction profiler.

       --branch-sim=<yes|no> [default: no]
           Specify if you want to do branch prediction simulation. Further event
           counters are enabled: Number of executed conditional branches and
           related predictor misses ("Bc"/"Bcm"), executed indirect jumps and
           related misses of the jump address predictor ("Bi"/"Bim").

       --free-is-write=no|yes [default: no]
           When enabled (not the default), Helgrind treats freeing of heap
           memory as if the memory was written immediately before the free. This
           exposes races where memory is referenced by one thread, and freed by
           another, but there is no observable synchronisation event to ensure
           that the reference happens before the free.

           This functionality is new in Valgrind 3.7.0, and is regarded as
           experimental. It is not enabled by default because its interaction
           with custom memory allocators is not well understood at present. User
           feedback is welcomed.

       --track-lockorders=no|yes [default: yes]
           When enabled (the default), Helgrind performs lock order consistency
           checking. For some buggy programs, the large number of lock order
           errors reported can become annoying, particularly if you're only
           interested in race errors. You may therefore find it helpful to
           disable lock order checking.

       --history-level=none|approx|full [default: full]
           --history-level=full (the default) causes Helgrind collects enough
           information about "old" accesses that it can produce two stack traces
           in a race report -- both the stack trace for the current access, and
           the trace for the older, conflicting access. To limit memory usage,
           "old" accesses stack traces are limited to a maximum of 8 entries,
           even if --num-callers value is bigger.

           Collecting such information is expensive in both speed and memory,
           particularly for programs that do many inter-thread synchronisation
           events (locks, unlocks, etc). Without such information, it is more
           difficult to track down the root causes of races. Nonetheless, you
           may not need it in situations where you just want to check for the
           presence or absence of races, for example, when doing regression
           testing of a previously race-free program.

           --history-level=none is the opposite extreme. It causes Helgrind not
           to collect any information about previous accesses. This can be
           dramatically faster than --history-level=full.

           --history-level=approx provides a compromise between these two
           extremes. It causes Helgrind to show a full trace for the later
           access, and approximate information regarding the earlier access.
           This approximate information consists of two stacks, and the earlier
           access is guaranteed to have occurred somewhere between program
           points denoted by the two stacks. This is not as useful as showing
           the exact stack for the previous access (as --history-level=full
           does), but it is better than nothing, and it is almost as fast as

       --delta-stacktrace=no|yes [default: yes on linux amd64/x86]
           This flag only has any effect at --history-level=full.

           --delta-stacktrace configures the way Helgrind captures the
           stacktraces for the option --history-level=full. Such a stacktrace is
           typically needed each time a new piece of memory is read or written
           in a basic block of instructions.

           --delta-stacktrace=no causes Helgrind to compute a full history
           stacktrace from the unwind info each time a stacktrace is needed.

           --delta-stacktrace=yes indicates to Helgrind to derive a new
           stacktrace from the previous stacktrace, as long as there was no call
           instruction, no return instruction, or any other instruction changing
           the call stack since the previous stacktrace was captured. If no such
           instruction was executed, the new stacktrace can be derived from the
           previous stacktrace by just changing the top frame to the current
           program counter. This option can speed up Helgrind by 25% when using

           The following aspects have to be considered when using
           --delta-stacktrace=yes :

           •   In some cases (for example in a function prologue), the valgrind
               unwinder might not properly unwind the stack, due to some
               limitations and/or due to wrong unwind info. When using
               --delta-stacktrace=yes, the wrong stack trace captured in the
               function prologue will be kept till the next call or return.

           •   On the other hand, --delta-stacktrace=yes sometimes helps to
               obtain a correct stacktrace, for example when the unwind info
               allows a correct stacktrace to be done in the beginning of the
               sequence, but not later on in the instruction sequence.

           •   Determining which instructions are changing the callstack is
               partially based on platform dependent heuristics, which have to
               be tuned/validated specifically for the platform. Also, unwinding
               in a function prologue must be good enough to allow using
               --delta-stacktrace=yes. Currently, the option
               --delta-stacktrace=yes has been reasonably validated only on
               linux x86 32 bits and linux amd64 64 bits. For more details about
               how to validate --delta-stacktrace=yes, see debug option
               --hg-sanity-flags and the function check_cached_rcec_ok in

       --conflict-cache-size=N [default: 1000000]
           This flag only has any effect at --history-level=full.

           Information about "old" conflicting accesses is stored in a cache of
           limited size, with LRU-style management. This is necessary because it
           isn't practical to store a stack trace for every single memory access
           made by the program. Historical information on not recently accessed
           locations is periodically discarded, to free up space in the cache.

           This option controls the size of the cache, in terms of the number of
           different memory addresses for which conflicting access information
           is stored. If you find that Helgrind is showing race errors with only
           one stack instead of the expected two stacks, try increasing this

           The minimum value is 10,000 and the maximum is 30,000,000 (thirty
           times the default value). Increasing the value by 1 increases
           Helgrind's memory requirement by very roughly 100 bytes, so the
           maximum value will easily eat up three extra gigabytes or so of

       --check-stack-refs=no|yes [default: yes]
           By default Helgrind checks all data memory accesses made by your
           program. This flag enables you to skip checking for accesses to
           thread stacks (local variables). This can improve performance, but
           comes at the cost of missing races on stack-allocated data.

       --ignore-thread-creation=<yes|no> [default: no]
           Controls whether all activities during thread creation should be
           ignored. By default enabled only on Solaris. Solaris provides higher
           throughput, parallelism and scalability than other operating systems,
           at the cost of more fine-grained locking activity. This means for
           example that when a thread is created under glibc, just one big lock
           is used for all thread setup. Solaris libc uses several fine-grained
           locks and the creator thread resumes its activities as soon as
           possible, leaving for example stack and TLS setup sequence to the
           created thread. This situation confuses Helgrind as it assumes there
           is some false ordering in place between creator and created thread;
           and therefore many types of race conditions in the application would
           not be reported. To prevent such false ordering, this command line
           option is set to yes by default on Solaris. All activity (loads,
           stores, client requests) is therefore ignored during:

           •   pthread_create() call in the creator thread

           •   thread creation phase (stack and TLS setup) in the created thread

           Also new memory allocated during thread creation is untracked, that
           is race reporting is suppressed there. DRD does the same thing
           implicitly. This is necessary because Solaris libc caches many
           objects and reuses them for different threads and that confuses

       --check-stack-var=<yes|no> [default: no]
           Controls whether DRD detects data races on stack variables. Verifying
           stack variables is disabled by default because most programs do not
           share stack variables over threads.

       --exclusive-threshold=<n> [default: off]
           Print an error message if any mutex or writer lock has been held
           longer than the time specified in milliseconds. This option enables
           the detection of lock contention.

       --join-list-vol=<n> [default: 10]
           Data races that occur between a statement at the end of one thread
           and another thread can be missed if memory access information is
           discarded immediately after a thread has been joined. This option
           allows one to specify for how many joined threads memory access
           information should be retained.

        --first-race-only=<yes|no> [default: no]
           Whether to report only the first data race that has been detected on
           a memory location or all data races that have been detected on a
           memory location.

        --free-is-write=<yes|no> [default: no]
           Whether to report races between accessing memory and freeing memory.
           Enabling this option may cause DRD to run slightly slower. Notes:

           •   Don't enable this option when using custom memory allocators that
               use the VG_USERREQ__MALLOCLIKE_BLOCK and
               VG_USERREQ__FREELIKE_BLOCK because that would result in false

           •   Don't enable this option when using reference-counted objects
               because that will result in false positives, even when that code
               has been annotated properly with ANNOTATE_HAPPENS_BEFORE and
               ANNOTATE_HAPPENS_AFTER. See e.g. the output of the following
               command for an example: valgrind --tool=drd --free-is-write=yes

        --report-signal-unlocked=<yes|no> [default: yes]
           Whether to report calls to pthread_cond_signal and
           pthread_cond_broadcast where the mutex associated with the signal
           through pthread_cond_wait or pthread_cond_timed_waitis not locked at
           the time the signal is sent. Sending a signal without holding a lock
           on the associated mutex is a common programming error which can cause
           subtle race conditions and unpredictable behavior. There exist some
           uncommon synchronization patterns however where it is safe to send a
           signal without holding a lock on the associated mutex.

       --segment-merging=<yes|no> [default: yes]
           Controls segment merging. Segment merging is an algorithm to limit
           memory usage of the data race detection algorithm. Disabling segment
           merging may improve the accuracy of the so-called 'other segments'
           displayed in race reports but can also trigger an out of memory

       --segment-merging-interval=<n> [default: 10]
           Perform segment merging only after the specified number of new
           segments have been created. This is an advanced configuration option
           that allows one to choose whether to minimize DRD's memory usage by
           choosing a low value or to let DRD run faster by choosing a slightly
           higher value. The optimal value for this parameter depends on the
           program being analyzed. The default value works well for most

       --shared-threshold=<n> [default: off]
           Print an error message if a reader lock has been held longer than the
           specified time (in milliseconds). This option enables the detection
           of lock contention.

       --show-confl-seg=<yes|no> [default: yes]
           Show conflicting segments in race reports. Since this information can
           help to find the cause of a data race, this option is enabled by
           default. Disabling this option makes the output of DRD more compact.

       --show-stack-usage=<yes|no> [default: no]
           Print stack usage at thread exit time. When a program creates a large
           number of threads it becomes important to limit the amount of virtual
           memory allocated for thread stacks. This option makes it possible to
           observe how much stack memory has been used by each thread of the
           client program. Note: the DRD tool itself allocates some temporary
           data on the client thread stack. The space necessary for this
           temporary data must be allocated by the client program when it
           allocates stack memory, but is not included in stack usage reported
           by DRD.

       --ignore-thread-creation=<yes|no> [default: no]
           Controls whether all activities during thread creation should be
           ignored. By default enabled only on Solaris. Solaris provides higher
           throughput, parallelism and scalability than other operating systems,
           at the cost of more fine-grained locking activity. This means for
           example that when a thread is created under glibc, just one big lock
           is used for all thread setup. Solaris libc uses several fine-grained
           locks and the creator thread resumes its activities as soon as
           possible, leaving for example stack and TLS setup sequence to the
           created thread. This situation confuses DRD as it assumes there is
           some false ordering in place between creator and created thread; and
           therefore many types of race conditions in the application would not
           be reported. To prevent such false ordering, this command line option
           is set to yes by default on Solaris. All activity (loads, stores,
           client requests) is therefore ignored during:

           •   pthread_create() call in the creator thread

           •   thread creation phase (stack and TLS setup) in the created thread

       --trace-addr=<address> [default: none]
           Trace all load and store activity for the specified address. This
           option may be specified more than once.

       --ptrace-addr=<address> [default: none]
           Trace all load and store activity for the specified address and keep
           doing that even after the memory at that address has been freed and

       --trace-alloc=<yes|no> [default: no]
           Trace all memory allocations and deallocations. May produce a huge
           amount of output.

       --trace-barrier=<yes|no> [default: no]
           Trace all barrier activity.

       --trace-cond=<yes|no> [default: no]
           Trace all condition variable activity.

       --trace-fork-join=<yes|no> [default: no]
           Trace all thread creation and all thread termination events.

       --trace-hb=<yes|no> [default: no]
           Trace execution of the ANNOTATE_HAPPENS_BEFORE(),
           ANNOTATE_HAPPENS_AFTER() and ANNOTATE_HAPPENS_DONE() client requests.

       --trace-mutex=<yes|no> [default: no]
           Trace all mutex activity.

       --trace-rwlock=<yes|no> [default: no]
           Trace all reader-writer lock activity.

       --trace-semaphore=<yes|no> [default: no]
           Trace all semaphore activity.

       --heap=<yes|no> [default: yes]
           Specifies whether heap profiling should be done.

       --heap-admin=<size> [default: 8]
           If heap profiling is enabled, gives the number of administrative
           bytes per block to use. This should be an estimate of the average,
           since it may vary. For example, the allocator used by glibc on Linux
           requires somewhere between 4 to 15 bytes per block, depending on
           various factors. That allocator also requires admin space for freed
           blocks, but Massif cannot account for this.

       --stacks=<yes|no> [default: no]
           Specifies whether stack profiling should be done. This option slows
           Massif down greatly, and so is off by default. Note that Massif
           assumes that the main stack has size zero at start-up. This is not
           true, but doing otherwise accurately is difficult. Furthermore,
           starting at zero better indicates the size of the part of the main
           stack that a user program actually has control over.

       --pages-as-heap=<yes|no> [default: no]
           Tells Massif to profile memory at the page level rather than at the
           malloc'd block level. See above for details.

       --depth=<number> [default: 30]
           Maximum depth of the allocation trees recorded for detailed
           snapshots. Increasing it will make Massif run somewhat more slowly,
           use more memory, and produce bigger output files.

           Functions specified with this option will be treated as though they
           were a heap allocation function such as malloc. This is useful for
           functions that are wrappers to malloc or new, which can fill up the
           allocation trees with uninteresting information. This option can be
           specified multiple times on the command line, to name multiple

           Note that the named function will only be treated this way if it is
           the top entry in a stack trace, or just below another function
           treated this way. For example, if you have a function malloc1 that
           wraps malloc, and malloc2 that wraps malloc1, just specifying
           --alloc-fn=malloc2 will have no effect. You need to specify
           --alloc-fn=malloc1 as well. This is a little inconvenient, but the
           reason is that checking for allocation functions is slow, and it
           saves a lot of time if Massif can stop looking through the stack
           trace entries as soon as it finds one that doesn't match rather than
           having to continue through all the entries.

           Note that C++ names are demangled. Note also that overloaded C++
           names must be written in full. Single quotes may be necessary to
           prevent the shell from breaking them up. For example:

               --alloc-fn='operator new(unsigned, std::nothrow_t const&)'

           Any direct heap allocation (i.e. a call to malloc, new, etc, or a
           call to a function named by an --alloc-fn option) that occurs in a
           function specified by this option will be ignored. This is mostly
           useful for testing purposes. This option can be specified multiple
           times on the command line, to name multiple functions.

           Any realloc of an ignored block will also be ignored, even if the
           realloc call does not occur in an ignored function. This avoids the
           possibility of negative heap sizes if ignored blocks are shrunk with

           The rules for writing C++ function names are the same as for
           --alloc-fn above.

       --threshold=<m.n> [default: 1.0]
           The significance threshold for heap allocations, as a percentage of
           total memory size. Allocation tree entries that account for less than
           this will be aggregated. Note that this should be specified in tandem
           with ms_print's option of the same name.

       --peak-inaccuracy=<m.n> [default: 1.0]
           Massif does not necessarily record the actual global memory
           allocation peak; by default it records a peak only when the global
           memory allocation size exceeds the previous peak by at least 1.0%.
           This is because there can be many local allocation peaks along the
           way, and doing a detailed snapshot for every one would be expensive
           and wasteful, as all but one of them will be later discarded. This
           inaccuracy can be changed (even to 0.0%) via this option, but Massif
           will run drastically slower as the number approaches zero.

       --time-unit=<i|ms|B> [default: i]
           The time unit used for the profiling. There are three possibilities:
           instructions executed (i), which is good for most cases; real
           (wallclock) time (ms, i.e. milliseconds), which is sometimes useful;
           and bytes allocated/deallocated on the heap and/or stack (B), which
           is useful for very short-run programs, and for testing purposes,
           because it is the most reproducible across different machines.

       --detailed-freq=<n> [default: 10]
           Frequency of detailed snapshots. With --detailed-freq=1, every
           snapshot is detailed.

       --max-snapshots=<n> [default: 100]
           The maximum number of snapshots recorded. If set to N, for all
           programs except very short-running ones, the final number of
           snapshots will be between N/2 and N.

       --massif-out-file=<file> [default: massif.out.%p]
           Write the profile data to file rather than to the default output
           file, massif.out.<pid>. The %p and %q format specifiers can be used
           to embed the process ID and/or the contents of an environment
           variable in the name, as is the case for the core option --log-file.

       --bb-out-file=<name> [default: bb.out.%p]
           This option selects the name of the basic block vector file. The %p
           and %q format specifiers can be used to embed the process ID and/or
           the contents of an environment variable in the name, as is the case
           for the core option --log-file.

       --pc-out-file=<name> [default: pc.out.%p]
           This option selects the name of the PC file. This file holds program
           counter addresses and function name info for the various basic
           blocks. This can be used in conjunction with the basic block vector
           file to fast-forward via function names instead of just instruction
           counts. The %p and %q format specifiers can be used to embed the
           process ID and/or the contents of an environment variable in the
           name, as is the case for the core option --log-file.

       --interval-size=<number> [default: 100000000]
           This option selects the size of the interval to use. The default is
           100 million instructions, which is a commonly used value. Other sizes
           can be used; smaller intervals can help programs with finer-grained
           phases. However smaller interval size can lead to accuracy issues due
           to warm-up effects (When fast-forwarding the various architectural
           features will be un-initialized, and it will take some number of
           instructions before they "warm up" to the state a full simulation
           would be at without the fast-forwarding. Large interval sizes tend to
           mitigate this.)

       --instr-count-only [default: no]
           This option tells the tool to only display instruction count totals,
           and to not generate the actual basic block vector file. This is
           useful for debugging, and for gathering instruction count info
           without generating the large basic block vector files.

       --basic-counts=<no|yes> [default: yes]
           When enabled, Lackey prints the following statistics and information
           about the execution of the client program:

            1. The number of calls to the function specified by the --fnname
               option (the default is main). If the program has had its symbols
               stripped, the count will always be zero.

            2. The number of conditional branches encountered and the number and
               proportion of those taken.

            3. The number of superblocks entered and completed by the program.
               Note that due to optimisations done by the JIT, this is not at
               all an accurate value.

            4. The number of guest (x86, amd64, ppc, etc.) instructions and IR
               statements executed. IR is Valgrind's RISC-like intermediate
               representation via which all instrumentation is done.

            5. Ratios between some of these counts.

            6. The exit code of the client program.

       --detailed-counts=<no|yes> [default: no]
           When enabled, Lackey prints a table containing counts of loads,
           stores and ALU operations, differentiated by their IR types. The IR
           types are identified by their IR name ("I1", "I8", ... "I128", "F32",
           "F64", and "V128").

       --trace-mem=<no|yes> [default: no]
           When enabled, Lackey prints the size and address of almost every
           memory access made by the program. See the comments at the top of the
           file lackey/lk_main.c for details about the output format, how it
           works, and inaccuracies in the address trace. Note that this option
           produces immense amounts of output.

       --trace-superblocks=<no|yes> [default: no]
           When enabled, Lackey prints out the address of every superblock (a
           single entry, multiple exit, linear chunk of code) executed by the
           program. This is primarily of interest to Valgrind developers. See
           the comments at the top of the file lackey/lk_main.c for details
           about the output format. Note that this option produces large amounts
           of output.

       --fnname=<name> [default: main]
           Changes the function for which calls are counted when
           --basic-counts=yes is specified.

       Valgrind supports the downloading of debuginfo files via debuginfod, an
       HTTP server for distributing ELF/DWARF debugging information. When a
       debuginfo file cannot be found locally, Valgrind is able to query
       debuginfod servers for the file using its build-id.

       In order to use this feature debuginfod-find must be installed and
       $DEBUGINFOD_URLS must contain URLs of debuginfod servers. Valgrind does
       not support debuginfod-find verbose output that is normally enabled with
       $DEBUGINFOD_PROGRESS and $DEBUGINFOD_VERBOSE. These environment variables
       will be ignored.

       For more information regarding debuginfod, see

       cg_annotate(1), callgrind_annotate(1), callgrind_control(1), ms_print(1),
       $INSTALL/share/doc/valgrind/html/index.html or, Debugging your program
       using Valgrind's gdbserver and GDB[1] vgdb[2], Valgrind monitor
       commands[3], The Commentary[4], Scheduling and Multi-Thread
       Performance[5], Cachegrind: a cache and branch-prediction profiler[6].
       Execution Trees[7]

       See the AUTHORS file in the valgrind distribution for a comprehensive
       list of authors.

       This manpage was written by Andres Roldan <> and the
       Valgrind developers.

        1. Debugging your program using Valgrind's gdbserver and GDB

        2. vgdb

        3. Valgrind monitor commands

        4. The Commentary

        5. Scheduling and Multi-Thread Performance

        6. Cachegrind: a cache and branch-prediction profiler

        7. Execution Trees

Release 3.17.0                     05/20/2021                        VALGRIND(1)