3 perlintern - autogenerated documentation of purely B<internal>
8 This file is the autogenerated documentation of functions in the
9 Perl interpreter that are documented using Perl's internal documentation
10 format but are not marked as part of the Perl API. In other words,
11 B<they are not for use in extensions>!
14 =head1 CV reference counts and CvOUTSIDE
20 Each CV has a pointer, C<CvOUTSIDE()>, to its lexically enclosing
21 CV (if any). Because pointers to anonymous sub prototypes are
22 stored in C<&> pad slots, it is a possible to get a circular reference,
23 with the parent pointing to the child and vice-versa. To avoid the
24 ensuing memory leak, we do not increment the reference count of the CV
25 pointed to by C<CvOUTSIDE> in the I<one specific instance> that the parent
26 has a C<&> pad slot pointing back to us. In this case, we set the
27 C<CvWEAKOUTSIDE> flag in the child. This allows us to determine under what
28 circumstances we should decrement the refcount of the parent when freeing
31 There is a further complication with non-closure anonymous subs (ie those
32 that do not refer to any lexicals outside that sub). In this case, the
33 anonymous prototype is shared rather than being cloned. This has the
34 consequence that the parent may be freed while there are still active
37 BEGIN { $a = sub { eval '$x' } }
39 In this case, the BEGIN is freed immediately after execution since there
40 are no active references to it: the anon sub prototype has
41 C<CvWEAKOUTSIDE> set since it's not a closure, and $a points to the same
42 CV, so it doesn't contribute to BEGIN's refcount either. When $a is
43 executed, the C<eval '$x'> causes the chain of C<CvOUTSIDE>s to be followed,
44 and the freed BEGIN is accessed.
46 To avoid this, whenever a CV and its associated pad is freed, any
47 C<&> entries in the pad are explicitly removed from the pad, and if the
48 refcount of the pointed-to anon sub is still positive, then that
49 child's C<CvOUTSIDE> is set to point to its grandparent. This will only
50 occur in the single specific case of a non-closure anon prototype
51 having one or more active references (such as C<$a> above).
53 One other thing to consider is that a CV may be merely undefined
54 rather than freed, eg C<undef &foo>. In this case, its refcount may
55 not have reached zero, but we still delete its pad and its C<CvROOT> etc.
56 Since various children may still have their C<CvOUTSIDE> pointing at this
57 undefined CV, we keep its own C<CvOUTSIDE> for the time being, so that
58 the chain of lexical scopes is unbroken. For example, the following
62 sub tmp { sub { eval '$x' } }
67 bool CvWEAKOUTSIDE(CV *cv)
75 =head1 Functions in file pad.h
82 Save the current pad in the given context block structure.
84 void CX_CURPAD_SAVE(struct context)
91 Access the SV at offset po in the saved current pad in the given
92 context block structure (can be used as an lvalue).
94 SV * CX_CURPAD_SV(struct context, PADOFFSET po)
101 Get the value from slot C<po> in the base (DEPTH=1) pad of a padlist
103 SV * PAD_BASE_SV (PADLIST padlist, PADOFFSET po)
111 Clone the state variables associated with running and compiling pads.
113 void PAD_CLONE_VARS(PerlInterpreter *proto_perl \)
118 =item PAD_COMPNAME_FLAGS
120 Return the flags for the current compiling pad name
121 at offset C<po>. Assumes a valid slot entry.
123 U32 PAD_COMPNAME_FLAGS(PADOFFSET po)
128 =item PAD_COMPNAME_GEN
130 The generation number of the name at offset C<po> in the current
131 compiling pad (lvalue). Note that C<SvCUR> is hijacked for this purpose.
133 STRLEN PAD_COMPNAME_GEN(PADOFFSET po)
138 =item PAD_COMPNAME_OURSTASH
140 Return the stash associated with an C<our> variable.
141 Assumes the slot entry is a valid C<our> lexical.
143 HV * PAD_COMPNAME_OURSTASH(PADOFFSET po)
148 =item PAD_COMPNAME_PV
150 Return the name of the current compiling pad name
151 at offset C<po>. Assumes a valid slot entry.
153 char * PAD_COMPNAME_PV(PADOFFSET po)
158 =item PAD_COMPNAME_TYPE
160 Return the type (stash) of the current compiling pad name at offset
161 C<po>. Must be a valid name. Returns null if not typed.
163 HV * PAD_COMPNAME_TYPE(PADOFFSET po)
172 void PAD_DUP(PADLIST dstpad, PADLIST srcpad, CLONE_PARAMS* param)
177 =item PAD_RESTORE_LOCAL
179 Restore the old pad saved into the local variable opad by PAD_SAVE_LOCAL()
181 void PAD_RESTORE_LOCAL(PAD *opad)
188 Save the current pad to the local variable opad, then make the
189 current pad equal to npad
191 void PAD_SAVE_LOCAL(PAD *opad, PAD *npad)
196 =item PAD_SAVE_SETNULLPAD
198 Save the current pad then set it to null.
200 void PAD_SAVE_SETNULLPAD()
207 Set the slot at offset C<po> in the current pad to C<sv>
209 SV * PAD_SETSV (PADOFFSET po, SV* sv)
216 Set the current pad to be pad C<n> in the padlist, saving
217 the previous current pad.
219 void PAD_SET_CUR (PADLIST padlist, I32 n)
224 =item PAD_SET_CUR_NOSAVE
226 like PAD_SET_CUR, but without the save
228 void PAD_SET_CUR_NOSAVE (PADLIST padlist, I32 n)
235 Get the value at offset C<po> in the current pad
237 void PAD_SV (PADOFFSET po)
244 Lightweight and lvalue version of C<PAD_SV>.
245 Get or set the value at offset C<po> in the current pad.
246 Unlike C<PAD_SV>, does not print diagnostics with -DX.
247 For internal use only.
249 SV * PAD_SVl (PADOFFSET po)
256 Clear the pointed to pad value on scope exit. (ie the runtime action of 'my')
258 void SAVECLEARSV (SV **svp)
265 save PL_comppad and PL_curpad
278 Save a pad slot (used to restore after an iteration)
280 XXX DAPM it would make more sense to make the arg a PADOFFSET
281 void SAVEPADSV (PADOFFSET po)
289 =head1 Functions in file pp_ctl.c
296 Locate the CV corresponding to the currently executing sub or eval.
297 If db_seqp is non_null, skip CVs that are in the DB package and populate
298 *db_seqp with the cop sequence number at the point that the DB:: code was
299 entered. (allows debuggers to eval in the scope of the breakpoint rather
300 than in in the scope of the debugger itself).
302 CV* find_runcv(U32 *db_seqp)
305 Found in file pp_ctl.c
310 =head1 Global Variables
316 When Perl is run in debugging mode, with the B<-d> switch, this SV is a
317 boolean which indicates whether subs are being single-stepped.
318 Single-stepping is automatically turned on after every step. This is the C
319 variable which corresponds to Perl's $DB::single variable. See
325 Found in file intrpvar.h
329 When Perl is run in debugging mode, with the B<-d> switch, this GV contains
330 the SV which holds the name of the sub being debugged. This is the C
331 variable which corresponds to Perl's $DB::sub variable. See
337 Found in file intrpvar.h
341 Trace variable used when Perl is run in debugging mode, with the B<-d>
342 switch. This is the C variable which corresponds to Perl's $DB::trace
343 variable. See C<PL_DBsingle>.
348 Found in file intrpvar.h
352 The C variable which corresponds to Perl's $^W warning variable.
357 Found in file intrpvar.h
361 The GV which was last used for a filehandle input operation. (C<< <FH> >>)
366 Found in file thrdvar.h
370 The output field separator - C<$,> in Perl space.
375 Found in file thrdvar.h
379 The input record separator - C<$/> in Perl space.
384 Found in file thrdvar.h
395 Returns C<TRUE> if given the name of a magical GV.
397 Currently only useful internally when determining if a GV should be
398 created even in rvalue contexts.
400 C<flags> is not used at present but available for future extension to
401 allow selecting particular classes of magical variable.
403 Currently assumes that C<name> is NUL terminated (as well as len being valid).
404 This assumption is met by all callers within the perl core, which all pass
405 pointers returned by SvPV.
407 bool is_gv_magical(char *name, STRLEN len, U32 flags)
421 Function called by C<do_readline> to spawn a glob (or do the glob inside
422 perl on VMS). This code used to be inline, but now perl uses C<File::Glob>
423 this glob starter is only used by miniperl during the build process.
424 Moving it away shrinks pp_hot.c; shrinking pp_hot.c helps speed perl up.
426 PerlIO* start_glob(SV* pattern, IO *io)
434 =head1 Pad Data Structures
440 CV's can have CvPADLIST(cv) set to point to an AV.
442 For these purposes "forms" are a kind-of CV, eval""s are too (except they're
443 not callable at will and are always thrown away after the eval"" is done
444 executing). Require'd files are simply evals without any outer lexical
447 XSUBs don't have CvPADLIST set - dXSTARG fetches values from PL_curpad,
448 but that is really the callers pad (a slot of which is allocated by
451 The CvPADLIST AV has does not have AvREAL set, so REFCNT of component items
452 is managed "manual" (mostly in pad.c) rather than normal av.c rules.
453 The items in the AV are not SVs as for a normal AV, but other AVs:
455 0'th Entry of the CvPADLIST is an AV which represents the "names" or rather
456 the "static type information" for lexicals.
458 The CvDEPTH'th entry of CvPADLIST AV is an AV which is the stack frame at that
459 depth of recursion into the CV.
460 The 0'th slot of a frame AV is an AV which is @_.
461 other entries are storage for variables and op targets.
464 C<PL_comppad_name> is set to the names AV.
465 C<PL_comppad> is set to the frame AV for the frame CvDEPTH == 1.
466 C<PL_curpad> is set to the body of the frame AV (i.e. AvARRAY(PL_comppad)).
468 During execution, C<PL_comppad> and C<PL_curpad> refer to the live
469 frame of the currently executing sub.
471 Iterating over the names AV iterates over all possible pad
472 items. Pad slots that are SVs_PADTMP (targets/GVs/constants) end up having
473 &PL_sv_undef "names" (see pad_alloc()).
475 Only my/our variable (SVs_PADMY/SVs_PADOUR) slots get valid names.
476 The rest are op targets/GVs/constants which are statically allocated
477 or resolved at compile time. These don't have names by which they
478 can be looked up from Perl code at run time through eval"" like
479 my/our variables can be. Since they can't be looked up by "name"
480 but only by their index allocated at compile time (which is usually
481 in PL_op->op_targ), wasting a name SV for them doesn't make sense.
483 The SVs in the names AV have their PV being the name of the variable.
484 NV+1..IV inclusive is a range of cop_seq numbers for which the name is
485 valid. For typed lexicals name SV is SVt_PVMG and SvSTASH points at the
486 type. For C<our> lexicals, the type is SVt_PVGV, and GvSTASH points at the
487 stash of the associated global (so that duplicate C<our> delarations in the
488 same package can be detected). SvCUR is sometimes hijacked to
489 store the generation number during compilation.
491 If SvFAKE is set on the name SV, then that slot in the frame AV is
492 a REFCNT'ed reference to a lexical from "outside". In this case,
493 the name SV does not use NVX and IVX to store a cop_seq range, since it is
494 in scope throughout. Instead IVX stores some flags containing info about
495 the real lexical (is it declared in an anon, and is it capable of being
496 instantiated multiple times?), and for fake ANONs, NVX contains the index
497 within the parent's pad where the lexical's value is stored, to make
500 If the 'name' is '&' the corresponding entry in frame AV
501 is a CV representing a possible closure.
502 (SvFAKE and name of '&' is not a meaningful combination currently but could
503 become so if C<my sub foo {}> is implemented.)
505 Note that formats are treated as anon subs, and are cloned each time
506 write is called (if necessary).
508 The flag SVf_PADSTALE is cleared on lexicals each time the my() is executed,
509 and set on scope exit. This allows the 'Variable $x is not available' warning
510 to be generated in evals, such as
512 { my $x = 1; sub f { eval '$x'} } f();
514 AV * CvPADLIST(CV *cv)
521 Clone a CV: make a new CV which points to the same code etc, but which
522 has a newly-created pad built by copying the prototype pad and capturing
525 CV* cv_clone(CV* proto)
532 dump the contents of a CV
534 void cv_dump(CV *cv, char *title)
541 Dump the contents of a padlist
543 void do_dump_pad(I32 level, PerlIO *file, PADLIST *padlist, int full)
550 "Introduce" my variables to visible status.
559 Add an anon code entry to the current compiling pad
561 PADOFFSET pad_add_anon(SV* sv, OPCODE op_type)
568 Create a new name and associated PADMY SV in the current pad; return the
570 If C<typestash> is valid, the name is for a typed lexical; set the
571 name's stash to that value.
572 If C<ourstash> is valid, it's an our lexical, set the name's
573 GvSTASH to that value
575 If fake, it means we're cloning an existing entry
577 PADOFFSET pad_add_name(char *name, HV* typestash, HV* ourstash, bool clone)
584 Allocate a new my or tmp pad entry. For a my, simply push a null SV onto
585 the end of PL_comppad, but for a tmp, scan the pad from PL_padix upwards
586 for a slot which has no name and and no active value.
588 PADOFFSET pad_alloc(I32 optype, U32 tmptype)
593 =item pad_block_start
595 Update the pad compilation state variables on entry to a new block
597 void pad_block_start(int full)
604 Check for duplicate declarations: report any of:
605 * a my in the current scope with the same name;
606 * an our (anywhere in the pad) with the same name and the same stash
608 C<is_our> indicates that the name to check is an 'our' declaration
610 void pad_check_dup(char* name, bool is_our, HV* ourstash)
617 Find a named lexical anywhere in a chain of nested pads. Add fake entries
618 in the inner pads if it's found in an outer one.
620 Returns the offset in the bottom pad of the lex or the fake lex.
621 cv is the CV in which to start the search, and seq is the current cop_seq
622 to match against. If warn is true, print appropriate warnings. The out_*
623 vars return values, and so are pointers to where the returned values
624 should be stored. out_capture, if non-null, requests that the innermost
625 instance of the lexical is captured; out_name_sv is set to the innermost
626 matched namesv or fake namesv; out_flags returns the flags normally
627 associated with the IVX field of a fake namesv.
629 Note that pad_findlex() is recursive; it recurses up the chain of CVs,
630 then comes back down, adding fake entries as it goes. It has to be this way
631 because fake namesvs in anon protoypes have to store in NVX the index into
634 PADOFFSET pad_findlex(char *name, CV* cv, U32 seq, int warn, SV** out_capture, SV** out_name_sv, int *out_flags)
641 Given a lexical name, try to find its offset, first in the current pad,
642 or failing that, in the pads of any lexically enclosing subs (including
643 the complications introduced by eval). If the name is found in an outer pad,
644 then a fake entry is added to the current pad.
645 Returns the offset in the current pad, or NOT_IN_PAD on failure.
647 PADOFFSET pad_findmy(char* name)
652 =item pad_fixup_inner_anons
654 For any anon CVs in the pad, change CvOUTSIDE of that CV from
655 old_cv to new_cv if necessary. Needed when a newly-compiled CV has to be
656 moved to a pre-existing CV struct.
658 void pad_fixup_inner_anons(PADLIST *padlist, CV *old_cv, CV *new_cv)
665 Free the SV at offet po in the current pad.
667 void pad_free(PADOFFSET po)
674 Cleanup at end of scope during compilation: set the max seq number for
675 lexicals in this scope and warn of any lexicals that never got introduced.
684 Create a new compiling padlist, saving and updating the various global
685 vars at the same time as creating the pad itself. The following flags
686 can be OR'ed together:
688 padnew_CLONE this pad is for a cloned CV
689 padnew_SAVE save old globals
690 padnew_SAVESUB also save extra stuff for start of sub
692 PADLIST* pad_new(int flags)
699 Push a new pad frame onto the padlist, unless there's already a pad at
700 this depth, in which case don't bother creating a new one.
701 If has_args is true, give the new pad an @_ in slot zero.
703 void pad_push(PADLIST *padlist, int depth, int has_args)
710 Mark all the current temporaries for reuse
719 Set the entry at offset po in the current pad to sv.
720 Use the macro PAD_SETSV() rather than calling this function directly.
722 void pad_setsv(PADOFFSET po, SV* sv)
729 Abandon the tmp in the current pad at offset po and replace with a
732 void pad_swipe(PADOFFSET po, bool refadjust)
739 Tidy up a pad after we've finished compiling it:
740 * remove most stuff from the pads of anonsub prototypes;
744 void pad_tidy(padtidy_type type)
751 Free the padlist associated with a CV.
752 If parts of it happen to be current, we null the relevant
753 PL_*pad* global vars so that we don't have any dangling references left.
754 We also repoint the CvOUTSIDE of any about-to-be-orphaned
755 inner subs to the outer of this cv.
757 (This function should really be called pad_free, but the name was already
760 void pad_undef(CV* cv)
768 =head1 Stack Manipulation Macros
774 Declare Just C<SP>. This is actually identical to C<dSP>, and declares
775 a local copy of perl's stack pointer, available via the C<SP> macro.
776 See C<SP>. (Available for backward source code compatibility with the
777 old (Perl 5.005) thread model.)
786 True if this op will be the return value of an lvalue subroutine
794 =head1 SV Manipulation Functions
798 =item find_uninit_var
800 Find the name of the undefined variable (if any) that caused the operator o
801 to issue a "Use of uninitialized value" warning.
802 If match is true, only return a name if it's value matches uninit_sv.
803 So roughly speaking, if a unary operator (such as OP_COS) generates a
804 warning, then following the direct child of the op may yield an
805 OP_PADSV or OP_GV that gives the name of the undefined variable. On the
806 other hand, with OP_ADD there are two branches to follow, so we only print
807 the variable name if we get an exact match.
809 The name is returned as a mortal SV.
811 Assumes that PL_op is the op that originally triggered the error, and that
812 PL_comppad/PL_curpad points to the currently executing pad.
814 SV* find_uninit_var(OP* obase, SV* uninit_sv, bool top)
821 Print appropriate "Use of uninitialized variable" warning
823 void report_uninit(SV* uninit_sv)
830 Given a chunk of memory, link it to the head of the list of arenas,
831 and split it into a list of free SVs.
833 void sv_add_arena(char* ptr, U32 size, U32 flags)
840 Decrement the refcnt of each remaining SV, possibly triggering a
841 cleanup. This function may have to be called multiple times to free
842 SVs which are in complex self-referential hierarchies.
851 Attempt to destroy all objects not yet freed
860 Deallocate the memory used by all arenas. Note that all the individual SV
861 heads and bodies within the arenas must already have been freed.
863 void sv_free_arenas()
873 The autodocumentation system was originally added to the Perl core by
874 Benjamin Stuhl. Documentation is by whoever was kind enough to
875 document their functions.
879 perlguts(1), perlapi(1)
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