B - The Perl Compiler
use B;TheB 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 theO module for the user-visible part. TheB 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 theB 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 theB module as Perl objects of the appropriate class. The bulk of theB 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" methodREFCNT (corresponding to the C functionSvREFCNT).
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_).
This returns the function name as a string (e.g. pp_add, pp_rv2av).
This returns the op description from the global C PL_op_desc array (e.g. "addition" "array deref").
BTheB 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.
Return the (faked) CV corresponding to the main part of the Perl program.
Returns the AV object (i.e. in class B::AV) representing INIT blocks.
Returns the root op (i.e. an object in the appropriate B::OP-derived class) of the main part of the Perl program.
Returns the starting op of the main part of the Perl program.
Returns the AV object (i.e. in class B::AV) of the global comppadlist.
Returns the SV object corresponding to the C variablesv_undef.
Returns the SV object corresponding to the C variablesv_yes.
Returns the SV object corresponding to the C variablesv_no.
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. Ifwalkoptree_debug (q.v.) has been called to turn debugging on then the methodwalkoptree_debug is called on each op before METHOD is called.
Returns the current debugging flag forwalkoptree. If the optional DEBUG argument is non-zero, it sets the debugging flag to that. See the description ofwalkoptree above for what the debugging flag does.
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.
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 asmain_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.
Return the PP function name (e.g. "pp_add") of op number OPNUM.
Returns a string in the form "0x..." representing the value of the internal hash function used by perl on string STR.
Casts I to the internal I32 type used by that perl.
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.
Returns a double-quote-surrounded escaped version of STR which can be used as a string in C source code.
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.
In a perl compiled for threads, this returns a list of the special per-thread threadsv variables.
Load the contents of FILEHANDLE as bytecode. See documentation for theBytecode module inB::Backend for how to generate bytecode.
Malcolm Beattie,mbeattie@sable.ox.ac.uk
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