


lib::B(3p)       Perl Programmers Reference Guide      lib::B(3p)


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





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lib::B(3p)       Perl Programmers Reference Guide      lib::B(3p)


       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






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       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






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       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




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lib::B(3p)       Perl Programmers Reference Guide      lib::B(3p)


       PADLIST

       OUTSIDE

       XSUB

       XSUBANY

       CvFLAGS

       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
           PL_op_desc array (e.g. "addition" "array deref").





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       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




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lib::B(3p)       Perl Programmers Reference Guide      lib::B(3p)


       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.

       init_av
           Returns the AV object (i.e. in class B::AV)
           representing INIT blocks.





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lib::B(3p)       Perl Programmers Reference Guide      lib::B(3p)


       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.





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lib::B(3p)       Perl Programmers Reference Guide      lib::B(3p)


       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




















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