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_GEN_set
140 Sets the generation number of the name at offset C<po> in the current
141 ling pad (lvalue) to C<gen>. Note that C<SvCUR_set> is hijacked for this purpose.
143 STRLEN PAD_COMPNAME_GEN_set(PADOFFSET po, int gen)
148 =item PAD_COMPNAME_OURSTASH
150 Return the stash associated with an C<our> variable.
151 Assumes the slot entry is a valid C<our> lexical.
153 HV * PAD_COMPNAME_OURSTASH(PADOFFSET po)
158 =item PAD_COMPNAME_PV
160 Return the name of the current compiling pad name
161 at offset C<po>. Assumes a valid slot entry.
163 char * PAD_COMPNAME_PV(PADOFFSET po)
168 =item PAD_COMPNAME_TYPE
170 Return the type (stash) of the current compiling pad name at offset
171 C<po>. Must be a valid name. Returns null if not typed.
173 HV * PAD_COMPNAME_TYPE(PADOFFSET po)
182 void PAD_DUP(PADLIST dstpad, PADLIST srcpad, CLONE_PARAMS* param)
187 =item PAD_RESTORE_LOCAL
189 Restore the old pad saved into the local variable opad by PAD_SAVE_LOCAL()
191 void PAD_RESTORE_LOCAL(PAD *opad)
198 Save the current pad to the local variable opad, then make the
199 current pad equal to npad
201 void PAD_SAVE_LOCAL(PAD *opad, PAD *npad)
206 =item PAD_SAVE_SETNULLPAD
208 Save the current pad then set it to null.
210 void PAD_SAVE_SETNULLPAD()
217 Set the slot at offset C<po> in the current pad to C<sv>
219 SV * PAD_SETSV (PADOFFSET po, SV* sv)
226 Set the current pad to be pad C<n> in the padlist, saving
227 the previous current pad. NB currently this macro expands to a string too
228 long for some compilers, so it's best to replace it with
231 PAD_SET_CUR_NOSAVE(padlist,n);
234 void PAD_SET_CUR (PADLIST padlist, I32 n)
239 =item PAD_SET_CUR_NOSAVE
241 like PAD_SET_CUR, but without the save
243 void PAD_SET_CUR_NOSAVE (PADLIST padlist, I32 n)
250 Get the value at offset C<po> in the current pad
252 void PAD_SV (PADOFFSET po)
259 Lightweight and lvalue version of C<PAD_SV>.
260 Get or set the value at offset C<po> in the current pad.
261 Unlike C<PAD_SV>, does not print diagnostics with -DX.
262 For internal use only.
264 SV * PAD_SVl (PADOFFSET po)
271 Clear the pointed to pad value on scope exit. (ie the runtime action of 'my')
273 void SAVECLEARSV (SV **svp)
280 save PL_comppad and PL_curpad
293 Save a pad slot (used to restore after an iteration)
295 XXX DAPM it would make more sense to make the arg a PADOFFSET
296 void SAVEPADSV (PADOFFSET po)
304 =head1 Functions in file pp_ctl.c
311 Locate the CV corresponding to the currently executing sub or eval.
312 If db_seqp is non_null, skip CVs that are in the DB package and populate
313 *db_seqp with the cop sequence number at the point that the DB:: code was
314 entered. (allows debuggers to eval in the scope of the breakpoint rather
315 than in in the scope of the debugger itself).
317 CV* find_runcv(U32 *db_seqp)
320 Found in file pp_ctl.c
325 =head1 Global Variables
331 When Perl is run in debugging mode, with the B<-d> switch, this SV is a
332 boolean which indicates whether subs are being single-stepped.
333 Single-stepping is automatically turned on after every step. This is the C
334 variable which corresponds to Perl's $DB::single variable. See
340 Found in file intrpvar.h
344 When Perl is run in debugging mode, with the B<-d> switch, this GV contains
345 the SV which holds the name of the sub being debugged. This is the C
346 variable which corresponds to Perl's $DB::sub variable. See
352 Found in file intrpvar.h
356 Trace variable used when Perl is run in debugging mode, with the B<-d>
357 switch. This is the C variable which corresponds to Perl's $DB::trace
358 variable. See C<PL_DBsingle>.
363 Found in file intrpvar.h
367 The C variable which corresponds to Perl's $^W warning variable.
372 Found in file intrpvar.h
376 The GV which was last used for a filehandle input operation. (C<< <FH> >>)
381 Found in file thrdvar.h
385 The output field separator - C<$,> in Perl space.
390 Found in file thrdvar.h
394 The input record separator - C<$/> in Perl space.
399 Found in file thrdvar.h
410 Returns C<TRUE> if given the name of a magical GV.
412 Currently only useful internally when determining if a GV should be
413 created even in rvalue contexts.
415 C<flags> is not used at present but available for future extension to
416 allow selecting particular classes of magical variable.
418 Currently assumes that C<name> is NUL terminated (as well as len being valid).
419 This assumption is met by all callers within the perl core, which all pass
420 pointers returned by SvPV.
422 bool is_gv_magical(const char *name, STRLEN len, U32 flags)
427 =item is_gv_magical_sv
429 Returns C<TRUE> if given the name of a magical GV. Calls is_gv_magical.
431 bool is_gv_magical_sv(SV *name, U32 flags)
445 Function called by C<do_readline> to spawn a glob (or do the glob inside
446 perl on VMS). This code used to be inline, but now perl uses C<File::Glob>
447 this glob starter is only used by miniperl during the build process.
448 Moving it away shrinks pp_hot.c; shrinking pp_hot.c helps speed perl up.
450 PerlIO* start_glob(SV* pattern, IO *io)
458 =head1 Magical Functions
464 Copy some of the magic from an existing SV to new localized version of
465 that SV. Container magic (eg %ENV, $1, tie) gets copied, value magic
466 doesn't (eg taint, pos).
468 void mg_localize(SV* sv, SV* nsv)
476 =head1 Pad Data Structures
482 CV's can have CvPADLIST(cv) set to point to an AV.
484 For these purposes "forms" are a kind-of CV, eval""s are too (except they're
485 not callable at will and are always thrown away after the eval"" is done
486 executing). Require'd files are simply evals without any outer lexical
489 XSUBs don't have CvPADLIST set - dXSTARG fetches values from PL_curpad,
490 but that is really the callers pad (a slot of which is allocated by
493 The CvPADLIST AV has does not have AvREAL set, so REFCNT of component items
494 is managed "manual" (mostly in pad.c) rather than normal av.c rules.
495 The items in the AV are not SVs as for a normal AV, but other AVs:
497 0'th Entry of the CvPADLIST is an AV which represents the "names" or rather
498 the "static type information" for lexicals.
500 The CvDEPTH'th entry of CvPADLIST AV is an AV which is the stack frame at that
501 depth of recursion into the CV.
502 The 0'th slot of a frame AV is an AV which is @_.
503 other entries are storage for variables and op targets.
506 C<PL_comppad_name> is set to the names AV.
507 C<PL_comppad> is set to the frame AV for the frame CvDEPTH == 1.
508 C<PL_curpad> is set to the body of the frame AV (i.e. AvARRAY(PL_comppad)).
510 During execution, C<PL_comppad> and C<PL_curpad> refer to the live
511 frame of the currently executing sub.
513 Iterating over the names AV iterates over all possible pad
514 items. Pad slots that are SVs_PADTMP (targets/GVs/constants) end up having
515 &PL_sv_undef "names" (see pad_alloc()).
517 Only my/our variable (SVs_PADMY/SVs_PADOUR) slots get valid names.
518 The rest are op targets/GVs/constants which are statically allocated
519 or resolved at compile time. These don't have names by which they
520 can be looked up from Perl code at run time through eval"" like
521 my/our variables can be. Since they can't be looked up by "name"
522 but only by their index allocated at compile time (which is usually
523 in PL_op->op_targ), wasting a name SV for them doesn't make sense.
525 The SVs in the names AV have their PV being the name of the variable.
526 NV+1..IV inclusive is a range of cop_seq numbers for which the name is
527 valid. For typed lexicals name SV is SVt_PVMG and SvSTASH points at the
528 type. For C<our> lexicals, the type is SVt_PVGV, and GvSTASH points at the
529 stash of the associated global (so that duplicate C<our> delarations in the
530 same package can be detected). SvCUR is sometimes hijacked to
531 store the generation number during compilation.
533 If SvFAKE is set on the name SV, then that slot in the frame AV is
534 a REFCNT'ed reference to a lexical from "outside". In this case,
535 the name SV does not use NVX and IVX to store a cop_seq range, since it is
536 in scope throughout. Instead IVX stores some flags containing info about
537 the real lexical (is it declared in an anon, and is it capable of being
538 instantiated multiple times?), and for fake ANONs, NVX contains the index
539 within the parent's pad where the lexical's value is stored, to make
542 If the 'name' is '&' the corresponding entry in frame AV
543 is a CV representing a possible closure.
544 (SvFAKE and name of '&' is not a meaningful combination currently but could
545 become so if C<my sub foo {}> is implemented.)
547 Note that formats are treated as anon subs, and are cloned each time
548 write is called (if necessary).
550 The flag SVf_PADSTALE is cleared on lexicals each time the my() is executed,
551 and set on scope exit. This allows the 'Variable $x is not available' warning
552 to be generated in evals, such as
554 { my $x = 1; sub f { eval '$x'} } f();
556 AV * CvPADLIST(CV *cv)
563 Clone a CV: make a new CV which points to the same code etc, but which
564 has a newly-created pad built by copying the prototype pad and capturing
567 CV* cv_clone(CV* proto)
574 dump the contents of a CV
576 void cv_dump(const CV *cv, const char *title)
583 Dump the contents of a padlist
585 void do_dump_pad(I32 level, PerlIO *file, PADLIST *padlist, int full)
592 "Introduce" my variables to visible status.
601 Add an anon code entry to the current compiling pad
603 PADOFFSET pad_add_anon(SV* sv, OPCODE op_type)
610 Create a new name and associated PADMY SV in the current pad; return the
612 If C<typestash> is valid, the name is for a typed lexical; set the
613 name's stash to that value.
614 If C<ourstash> is valid, it's an our lexical, set the name's
615 GvSTASH to that value
617 If fake, it means we're cloning an existing entry
619 PADOFFSET pad_add_name(const char *name, HV* typestash, HV* ourstash, bool clone)
626 Allocate a new my or tmp pad entry. For a my, simply push a null SV onto
627 the end of PL_comppad, but for a tmp, scan the pad from PL_padix upwards
628 for a slot which has no name and and no active value.
630 PADOFFSET pad_alloc(I32 optype, U32 tmptype)
635 =item pad_block_start
637 Update the pad compilation state variables on entry to a new block
639 void pad_block_start(int full)
646 Check for duplicate declarations: report any of:
647 * a my in the current scope with the same name;
648 * an our (anywhere in the pad) with the same name and the same stash
650 C<is_our> indicates that the name to check is an 'our' declaration
652 void pad_check_dup(const char* name, bool is_our, const HV* ourstash)
659 Find a named lexical anywhere in a chain of nested pads. Add fake entries
660 in the inner pads if it's found in an outer one.
662 Returns the offset in the bottom pad of the lex or the fake lex.
663 cv is the CV in which to start the search, and seq is the current cop_seq
664 to match against. If warn is true, print appropriate warnings. The out_*
665 vars return values, and so are pointers to where the returned values
666 should be stored. out_capture, if non-null, requests that the innermost
667 instance of the lexical is captured; out_name_sv is set to the innermost
668 matched namesv or fake namesv; out_flags returns the flags normally
669 associated with the IVX field of a fake namesv.
671 Note that pad_findlex() is recursive; it recurses up the chain of CVs,
672 then comes back down, adding fake entries as it goes. It has to be this way
673 because fake namesvs in anon protoypes have to store in NVX the index into
676 PADOFFSET pad_findlex(const char *name, const CV* cv, U32 seq, int warn, SV** out_capture, SV** out_name_sv, int *out_flags)
683 Given a lexical name, try to find its offset, first in the current pad,
684 or failing that, in the pads of any lexically enclosing subs (including
685 the complications introduced by eval). If the name is found in an outer pad,
686 then a fake entry is added to the current pad.
687 Returns the offset in the current pad, or NOT_IN_PAD on failure.
689 PADOFFSET pad_findmy(const char* name)
694 =item pad_fixup_inner_anons
696 For any anon CVs in the pad, change CvOUTSIDE of that CV from
697 old_cv to new_cv if necessary. Needed when a newly-compiled CV has to be
698 moved to a pre-existing CV struct.
700 void pad_fixup_inner_anons(PADLIST *padlist, CV *old_cv, CV *new_cv)
707 Free the SV at offet po in the current pad.
709 void pad_free(PADOFFSET po)
716 Cleanup at end of scope during compilation: set the max seq number for
717 lexicals in this scope and warn of any lexicals that never got introduced.
726 Create a new compiling padlist, saving and updating the various global
727 vars at the same time as creating the pad itself. The following flags
728 can be OR'ed together:
730 padnew_CLONE this pad is for a cloned CV
731 padnew_SAVE save old globals
732 padnew_SAVESUB also save extra stuff for start of sub
734 PADLIST* pad_new(int flags)
741 Push a new pad frame onto the padlist, unless there's already a pad at
742 this depth, in which case don't bother creating a new one. Then give
743 the new pad an @_ in slot zero.
745 void pad_push(PADLIST *padlist, int depth)
752 Mark all the current temporaries for reuse
761 Set the entry at offset po in the current pad to sv.
762 Use the macro PAD_SETSV() rather than calling this function directly.
764 void pad_setsv(PADOFFSET po, SV* sv)
771 Abandon the tmp in the current pad at offset po and replace with a
774 void pad_swipe(PADOFFSET po, bool refadjust)
781 Tidy up a pad after we've finished compiling it:
782 * remove most stuff from the pads of anonsub prototypes;
786 void pad_tidy(padtidy_type type)
793 Free the padlist associated with a CV.
794 If parts of it happen to be current, we null the relevant
795 PL_*pad* global vars so that we don't have any dangling references left.
796 We also repoint the CvOUTSIDE of any about-to-be-orphaned
797 inner subs to the outer of this cv.
799 (This function should really be called pad_free, but the name was already
802 void pad_undef(CV* cv)
810 =head1 Stack Manipulation Macros
816 Declare Just C<SP>. This is actually identical to C<dSP>, and declares
817 a local copy of perl's stack pointer, available via the C<SP> macro.
818 See C<SP>. (Available for backward source code compatibility with the
819 old (Perl 5.005) thread model.)
828 True if this op will be the return value of an lvalue subroutine
836 =head1 SV Manipulation Functions
840 =item find_uninit_var
842 Find the name of the undefined variable (if any) that caused the operator o
843 to issue a "Use of uninitialized value" warning.
844 If match is true, only return a name if it's value matches uninit_sv.
845 So roughly speaking, if a unary operator (such as OP_COS) generates a
846 warning, then following the direct child of the op may yield an
847 OP_PADSV or OP_GV that gives the name of the undefined variable. On the
848 other hand, with OP_ADD there are two branches to follow, so we only print
849 the variable name if we get an exact match.
851 The name is returned as a mortal SV.
853 Assumes that PL_op is the op that originally triggered the error, and that
854 PL_comppad/PL_curpad points to the currently executing pad.
856 SV* find_uninit_var(OP* obase, SV* uninit_sv, bool top)
863 Print appropriate "Use of uninitialized variable" warning
865 void report_uninit(SV* uninit_sv)
872 Given a chunk of memory, link it to the head of the list of arenas,
873 and split it into a list of free SVs.
875 void sv_add_arena(char* ptr, U32 size, U32 flags)
882 Decrement the refcnt of each remaining SV, possibly triggering a
883 cleanup. This function may have to be called multiple times to free
884 SVs which are in complex self-referential hierarchies.
893 Attempt to destroy all objects not yet freed
902 Deallocate the memory used by all arenas. Note that all the individual SV
903 heads and bodies within the arenas must already have been freed.
905 void sv_free_arenas()
915 The autodocumentation system was originally added to the Perl core by
916 Benjamin Stuhl. Documentation is by whoever was kind enough to
917 document their functions.
921 perlguts(1), perlapi(1)
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