B

B(3)                   Perl Programmers Reference Guide                   B(3)



NAME
       B - The Perl Compiler

SYNOPSIS
               use B;


DESCRIPTION
       The B module supplies classes which allow a Perl program to delve into
       its own innards. It is the module used to implement the "backends" of
       the Perl compiler. Usage of the compiler does not require knowledge of
       this module: see the O module for the user-visible part. The B module
       is of use to those who want to write new compiler backends. This
       documentation assumes that the reader knows a fair amount about perl's
       internals including such things as SVs, OPs and the internal symbol
       table and syntax tree of a program.

OVERVIEW OF CLASSES
       The C structures used by Perl's internals to hold SV and OP information
       (PVIV, AV, HV, ..., OP, SVOP, UNOP, ...) are modelled on a class
       hierarchy and the B module gives access to them via a true object
       hierarchy. Structure fields which point to other objects (whether types
       of SV or types of OP) are represented by the B module as Perl objects
       of the appropriate class. The bulk of the B module is the methods for
       accessing fields of these structures. Note that all access is read-
       only: you cannot modify the internals by using this module.

       SV-RELATED CLASSES

       B::IV, B::NV, B::RV, B::PV, B::PVIV, B::PVNV, B::PVMG, B::BM, B::PVLV,
       B::AV, B::HV, B::CV, B::GV, B::FM, B::IO. These classes correspond in
       the obvious way to the underlying C structures of similar names. The
       inheritance hierarchy mimics the underlying C "inheritance". Access
       methods correspond to the underlying C macros for field access, usually
       with the leading "class indication" prefix removed (Sv, Av, Hv, ...).
       The leading prefix is only left in cases where its removal would cause
       a clash in method name. For example, GvREFCNT stays as-is since its
       abbreviation would clash with the "superclass" method REFCNT
       (corresponding to the C function SvREFCNT).

       B::SV METHODS

       REFCNT

       FLAGS

       B::IV METHODS

       IV

       IVX

       needs64bits

       packiv

       B::NV METHODS

       NV

       NVX

       B::RV METHODS

       RV

       B::PV METHODS

       PV

       B::PVMG METHODS

       MAGIC

       SvSTASH

       B::MAGIC METHODS

       MOREMAGIC

       PRIVATE

       TYPE

       FLAGS

       OBJ

       PTR

       B::PVLV METHODS

       TARGOFF

       TARGLEN

       TYPE

       TARG

       B::BM METHODS

       USEFUL

       PREVIOUS

       RARE

       TABLE

       B::GV METHODS

       NAME

       STASH

       SV

       IO

       FORM

       AV

       HV

       EGV

       CV

       CVGEN

       LINE

       FILEGV

       GvREFCNT

       FLAGS

       B::IO METHODS

       LINES

       PAGE

       PAGE_LEN

       LINES_LEFT

       TOP_NAME

       TOP_GV

       FMT_NAME

       FMT_GV

       BOTTOM_NAME

       BOTTOM_GV

       SUBPROCESS

       IoTYPE

       IoFLAGS

       B::AV METHODS

       FILL

       MAX

       OFF

       ARRAY

       AvFLAGS

       B::CV METHODS

       STASH

       START

       ROOT

       GV

       FILEGV

       DEPTH

       PADLIST

       OUTSIDE

       XSUB

       XSUBANY

       B::HV METHODS

       FILL

       MAX

       KEYS

       RITER

       NAME

       PMROOT

       ARRAY

       OP-RELATED CLASSES

       B::OP, B::UNOP, B::BINOP, B::LOGOP, B::CONDOP, B::LISTOP, B::PMOP,
       B::SVOP, B::GVOP, B::PVOP, B::CVOP, B::LOOP, B::COP.  These classes
       correspond in the obvious way to the underlying C structures of similar
       names. The inheritance hierarchy mimics the underlying C "inheritance".
       Access methods correspond to the underlying C structre field names,
       with the leading "class indication" prefix removed (op_).

       B::OP METHODS

       next

       sibling

       ppaddr
           This returns the function name as a string (e.g. pp_add, pp_rv2av).

       desc
           This returns the op description from the global C op_desc array
           (e.g. "addition" "array deref").

       targ

       type

       seq

       flags

       private

       B::UNOP METHOD

       first

       B::BINOP METHOD

       last

       B::LOGOP METHOD

       other

       B::CONDOP METHODS

       true

       false

       B::LISTOP METHOD

       children

       B::PMOP METHODS

       pmreplroot

       pmreplstart

       pmnext

       pmregexp

       pmflags

       pmpermflags

       precomp

       B::SVOP METHOD

       sv

       B::GVOP METHOD

       gv

       B::PVOP METHOD

       pv

       B::LOOP METHODS

       redoop

       nextop

       lastop

       B::COP METHODS

       label

       stash

       filegv

       cop_seq

       arybase

       line

FUNCTIONS EXPORTED BY B
       The B module exports a variety of functions: some are simple utility
       functions, others provide a Perl program with a way to get an initial
       "handle" on an internal object.

       main_cv
           Return the (faked) CV corresponding to the main part of the Perl
           program.

       main_root
           Returns the root op (i.e. an object in the appropriate
           B::OP-derived class) of the main part of the Perl program.

       main_start
           Returns the starting op of the main part of the Perl program.

       comppadlist
           Returns the AV object (i.e. in class B::AV) of the global
           comppadlist.

       sv_undef
           Returns the SV object corresponding to the C variable sv_undef.

       sv_yes
           Returns the SV object corresponding to the C variable sv_yes.

       sv_no
           Returns the SV object corresponding to the C variable sv_no.

       walkoptree(OP, METHOD)
           Does a tree-walk of the syntax tree based at OP and calls METHOD on
           each op it visits. Each node is visited before its children. If
           walkoptree_debug (q.v.) has been called to turn debugging on then
           the method walkoptree_debug is called on each op before METHOD is
           called.

       walkoptree_debug(DEBUG)
           Returns the current debugging flag for walkoptree. If the optional
           DEBUG argument is non-zero, it sets the debugging flag to that. See
           the description of walkoptree above for what the debugging flag
           does.

       walksymtable(SYMREF, METHOD, RECURSE)
           Walk the symbol table starting at SYMREF and call METHOD on each
           symbol visited. When the walk reached package symbols "Foo::" it
           invokes RECURSE and only recurses into the package if that sub
           returns true.

       svref_2object(SV)
           Takes any Perl variable and turns it into an object in the
           appropriate B::OP-derived or B::SV-derived class. Apart from
           functions such as main_root, this is the primary way to get an
           initial "handle" on a internal perl data structure which can then
           be followed with the other access methods.

       ppname(OPNUM)
           Return the PP function name (e.g. "pp_add") of op number OPNUM.

       hash(STR)
           Returns a string in the form "0x..." representing the value of the
           internal hash function used by perl on string STR.

       cast_I32(I)
           Casts I to the internal I32 type used by that perl.

       minus_c
           Does the equivalent of the -c command-line option. Obviously, this
           is only useful in a BEGIN block or else the flag is set too late.

       cstring(STR)
           Returns a double-quote-surrounded escaped version of STR which can
           be used as a string in C source code.

       class(OBJ)
           Returns the class of an object without the part of the classname
           preceding the first "::". This is used to turn "B::UNOP" into
           "UNOP" for example.

       threadsv_names
           In a perl compiled for threads, this returns a list of the special
           per-thread threadsv variables.

       byteload_fh(FILEHANDLE)
           Load the contents of FILEHANDLE as bytecode. See documentation for
           the Bytecode module in B::Backend for how to generate bytecode.

AUTHOR
       Malcolm Beattie, mbeattie@sable.ox.ac.uk







































































































































































3rd Berkeley Distribution    perl 5.005, patch 02                         B(3)