See also related modules.
B - The Perl Compiler
use B;
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.
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.
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).
- REFCNT
-
- FLAGS
-
- IV
-
- IVX
-
- needs64bits
-
- packiv
-
- NV
-
- NVX
-
- RV
-
- PV
-
- MAGIC
-
- SvSTASH
-
- MOREMAGIC
-
- PRIVATE
-
- TYPE
-
- FLAGS
-
- OBJ
-
- PTR
-
- TARGOFF
-
- TARGLEN
-
- TYPE
-
- TARG
-
- USEFUL
-
- PREVIOUS
-
- RARE
-
- TABLE
-
- NAME
-
- STASH
-
- SV
-
- IO
-
- FORM
-
- AV
-
- HV
-
- EGV
-
- CV
-
- CVGEN
-
- LINE
-
- FILEGV
-
- GvREFCNT
-
- FLAGS
-
- LINES
-
- PAGE
-
- PAGE_LEN
-
- LINES_LEFT
-
- TOP_NAME
-
- TOP_GV
-
- FMT_NAME
-
- FMT_GV
-
- BOTTOM_NAME
-
- BOTTOM_GV
-
- SUBPROCESS
-
- IoTYPE
-
- IoFLAGS
-
- FILL
-
- MAX
-
- OFF
-
- ARRAY
-
- AvFLAGS
-
- STASH
-
- START
-
- ROOT
-
- GV
-
- FILEGV
-
- DEPTH
-
- PADLIST
-
- OUTSIDE
-
- XSUB
-
- XSUBANY
-
- FILL
-
- MAX
-
- KEYS
-
- RITER
-
- NAME
-
- PMROOT
-
- ARRAY
-
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_).
- 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
-
- first
-
- last
-
- other
-
- true
-
- false
-
- children
-
- pmreplroot
-
- pmreplstart
-
- pmnext
-
- pmregexp
-
- pmflags
-
- pmpermflags
-
- precomp
-
- sv
-
- gv
-
- pv
-
- redoop
-
- nextop
-
- lastop
-
- label
-
- stash
-
- filegv
-
- cop_seq
-
- arybase
-
- line
-
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.
Malcolm Beattie, mbeattie@sable.ox.ac.uk
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