1 -*- buffer-read-only: t -*-
3 !!!!!!! DO NOT EDIT THIS FILE !!!!!!!
4 This file is built by autodoc.pl extracting documentation from the C source
9 perlintern - autogenerated documentation of purely B<internal>
13 X<internal Perl functions> X<interpreter functions>
15 This file is the autogenerated documentation of functions in the
16 Perl interpreter that are documented using Perl's internal documentation
17 format but are not marked as part of the Perl API. In other words,
18 B<they are not for use in extensions>!
21 =head1 CV reference counts and CvOUTSIDE
28 Each CV has a pointer, C<CvOUTSIDE()>, to its lexically enclosing
29 CV (if any). Because pointers to anonymous sub prototypes are
30 stored in C<&> pad slots, it is a possible to get a circular reference,
31 with the parent pointing to the child and vice-versa. To avoid the
32 ensuing memory leak, we do not increment the reference count of the CV
33 pointed to by C<CvOUTSIDE> in the I<one specific instance> that the parent
34 has a C<&> pad slot pointing back to us. In this case, we set the
35 C<CvWEAKOUTSIDE> flag in the child. This allows us to determine under what
36 circumstances we should decrement the refcount of the parent when freeing
39 There is a further complication with non-closure anonymous subs (i.e. those
40 that do not refer to any lexicals outside that sub). In this case, the
41 anonymous prototype is shared rather than being cloned. This has the
42 consequence that the parent may be freed while there are still active
45 BEGIN { $a = sub { eval '$x' } }
47 In this case, the BEGIN is freed immediately after execution since there
48 are no active references to it: the anon sub prototype has
49 C<CvWEAKOUTSIDE> set since it's not a closure, and $a points to the same
50 CV, so it doesn't contribute to BEGIN's refcount either. When $a is
51 executed, the C<eval '$x'> causes the chain of C<CvOUTSIDE>s to be followed,
52 and the freed BEGIN is accessed.
54 To avoid this, whenever a CV and its associated pad is freed, any
55 C<&> entries in the pad are explicitly removed from the pad, and if the
56 refcount of the pointed-to anon sub is still positive, then that
57 child's C<CvOUTSIDE> is set to point to its grandparent. This will only
58 occur in the single specific case of a non-closure anon prototype
59 having one or more active references (such as C<$a> above).
61 One other thing to consider is that a CV may be merely undefined
62 rather than freed, eg C<undef &foo>. In this case, its refcount may
63 not have reached zero, but we still delete its pad and its C<CvROOT> etc.
64 Since various children may still have their C<CvOUTSIDE> pointing at this
65 undefined CV, we keep its own C<CvOUTSIDE> for the time being, so that
66 the chain of lexical scopes is unbroken. For example, the following
70 sub tmp { sub { eval '$x' } }
75 bool CvWEAKOUTSIDE(CV *cv)
83 =head1 Functions in file pad.h
91 Save the current pad in the given context block structure.
93 void CX_CURPAD_SAVE(struct context)
101 Access the SV at offset po in the saved current pad in the given
102 context block structure (can be used as an lvalue).
104 SV * CX_CURPAD_SV(struct context, PADOFFSET po)
112 Get the value from slot C<po> in the base (DEPTH=1) pad of a padlist
114 SV * PAD_BASE_SV(PADLIST padlist, PADOFFSET po)
122 Clone the state variables associated with running and compiling pads.
124 void PAD_CLONE_VARS(PerlInterpreter *proto_perl, CLONE_PARAMS* param)
129 =item PAD_COMPNAME_FLAGS
130 X<PAD_COMPNAME_FLAGS>
132 Return the flags for the current compiling pad name
133 at offset C<po>. Assumes a valid slot entry.
135 U32 PAD_COMPNAME_FLAGS(PADOFFSET po)
140 =item PAD_COMPNAME_GEN
143 The generation number of the name at offset C<po> in the current
144 compiling pad (lvalue). Note that C<SvUVX> is hijacked for this purpose.
146 STRLEN PAD_COMPNAME_GEN(PADOFFSET po)
151 =item PAD_COMPNAME_GEN_set
152 X<PAD_COMPNAME_GEN_set>
154 Sets the generation number of the name at offset C<po> in the current
155 ling pad (lvalue) to C<gen>. Note that C<SvUV_set> is hijacked for this purpose.
157 STRLEN PAD_COMPNAME_GEN_set(PADOFFSET po, int gen)
162 =item PAD_COMPNAME_OURSTASH
163 X<PAD_COMPNAME_OURSTASH>
165 Return the stash associated with an C<our> variable.
166 Assumes the slot entry is a valid C<our> lexical.
168 HV * PAD_COMPNAME_OURSTASH(PADOFFSET po)
173 =item PAD_COMPNAME_PV
176 Return the name of the current compiling pad name
177 at offset C<po>. Assumes a valid slot entry.
179 char * PAD_COMPNAME_PV(PADOFFSET po)
184 =item PAD_COMPNAME_TYPE
187 Return the type (stash) of the current compiling pad name at offset
188 C<po>. Must be a valid name. Returns null if not typed.
190 HV * PAD_COMPNAME_TYPE(PADOFFSET po)
200 void PAD_DUP(PADLIST dstpad, PADLIST srcpad, CLONE_PARAMS* param)
205 =item PAD_RESTORE_LOCAL
208 Restore the old pad saved into the local variable opad by PAD_SAVE_LOCAL()
210 void PAD_RESTORE_LOCAL(PAD *opad)
218 Save the current pad to the local variable opad, then make the
219 current pad equal to npad
221 void PAD_SAVE_LOCAL(PAD *opad, PAD *npad)
226 =item PAD_SAVE_SETNULLPAD
227 X<PAD_SAVE_SETNULLPAD>
229 Save the current pad then set it to null.
231 void PAD_SAVE_SETNULLPAD()
239 Set the slot at offset C<po> in the current pad to C<sv>
241 SV * PAD_SETSV(PADOFFSET po, SV* sv)
249 Set the current pad to be pad C<n> in the padlist, saving
250 the previous current pad. NB currently this macro expands to a string too
251 long for some compilers, so it's best to replace it with
254 PAD_SET_CUR_NOSAVE(padlist,n);
257 void PAD_SET_CUR(PADLIST padlist, I32 n)
262 =item PAD_SET_CUR_NOSAVE
263 X<PAD_SET_CUR_NOSAVE>
265 like PAD_SET_CUR, but without the save
267 void PAD_SET_CUR_NOSAVE(PADLIST padlist, I32 n)
275 Get the value at offset C<po> in the current pad
277 void PAD_SV(PADOFFSET po)
285 Lightweight and lvalue version of C<PAD_SV>.
286 Get or set the value at offset C<po> in the current pad.
287 Unlike C<PAD_SV>, does not print diagnostics with -DX.
288 For internal use only.
290 SV * PAD_SVl(PADOFFSET po)
298 Clear the pointed to pad value on scope exit. (i.e. the runtime action of 'my')
300 void SAVECLEARSV(SV **svp)
308 save PL_comppad and PL_curpad
322 Save a pad slot (used to restore after an iteration)
324 XXX DAPM it would make more sense to make the arg a PADOFFSET
325 void SAVEPADSV(PADOFFSET po)
337 =item is_gv_magical_sv
340 Returns C<TRUE> if given the name of a magical GV.
342 Currently only useful internally when determining if a GV should be
343 created even in rvalue contexts.
345 C<flags> is not used at present but available for future extension to
346 allow selecting particular classes of magical variable.
348 Currently assumes that C<name> is NUL terminated (as well as len being valid).
349 This assumption is met by all callers within the perl core, which all pass
350 pointers returned by SvPV.
352 bool is_gv_magical_sv(SV *const name_sv, U32 flags)
360 =head1 Hash Manipulation Functions
364 =item refcounted_he_chain_2hv
365 X<refcounted_he_chain_2hv>
367 Generates and returns a C<HV *> by walking up the tree starting at the passed
368 in C<struct refcounted_he *>.
370 HV * refcounted_he_chain_2hv(const struct refcounted_he *c)
375 =item refcounted_he_free
376 X<refcounted_he_free>
378 Decrements the reference count of the passed in C<struct refcounted_he *>
379 by one. If the reference count reaches zero the structure's memory is freed,
380 and C<refcounted_he_free> iterates onto the parent node.
382 void refcounted_he_free(struct refcounted_he *he)
387 =item refcounted_he_new
390 Creates a new C<struct refcounted_he>. As S<key> is copied, and value is
391 stored in a compact form, all references remain the property of the caller.
392 The C<struct refcounted_he> is returned with a reference count of 1.
394 struct refcounted_he * refcounted_he_new(struct refcounted_he *const parent, SV *const key, SV *const value)
409 Function called by C<do_readline> to spawn a glob (or do the glob inside
410 perl on VMS). This code used to be inline, but now perl uses C<File::Glob>
411 this glob starter is only used by miniperl during the build process.
412 Moving it away shrinks pp_hot.c; shrinking pp_hot.c helps speed perl up.
414 PerlIO* start_glob(SV *tmpglob, IO *io)
422 =head1 Magical Functions
426 =item magic_clearhint
429 Triggered by a delete from %^H, records the key to
430 C<PL_compiling.cop_hints_hash>.
432 int magic_clearhint(SV* sv, MAGIC* mg)
440 Triggered by a store to %^H, records the key/value pair to
441 C<PL_compiling.cop_hints_hash>. It is assumed that hints aren't storing
442 anything that would need a deep copy. Maybe we should warn if we find a
445 int magic_sethint(SV* sv, MAGIC* mg)
453 Copy some of the magic from an existing SV to new localized version of that
454 SV. Container magic (eg %ENV, $1, tie) gets copied, value magic doesn't (eg
457 If setmagic is false then no set magic will be called on the new (empty) SV.
458 This typically means that assignment will soon follow (e.g. 'local $x = $y'),
459 and that will handle the magic.
461 void mg_localize(SV* sv, SV* nsv, bool setmagic)
473 =item mro_get_linear_isa_dfs
474 X<mro_get_linear_isa_dfs>
476 Returns the Depth-First Search linearization of @ISA
477 the given stash. The return value is a read-only AV*.
478 C<level> should be 0 (it is used internally in this
479 function's recursion).
481 You are responsible for C<SvREFCNT_inc()> on the
482 return value if you plan to store it anywhere
483 semi-permanently (otherwise it might be deleted
484 out from under you the next time the cache is
487 AV* mro_get_linear_isa_dfs(HV* stash, U32 level)
492 =item mro_isa_changed_in
493 X<mro_isa_changed_in>
495 Takes the necessary steps (cache invalidations, mostly)
496 when the @ISA of the given package has changed. Invoked
497 by the C<setisa> magic, should not need to invoke directly.
499 void mro_isa_changed_in(HV* stash)
507 =head1 Pad Data Structures
514 CV's can have CvPADLIST(cv) set to point to an AV.
516 For these purposes "forms" are a kind-of CV, eval""s are too (except they're
517 not callable at will and are always thrown away after the eval"" is done
518 executing). Require'd files are simply evals without any outer lexical
521 XSUBs don't have CvPADLIST set - dXSTARG fetches values from PL_curpad,
522 but that is really the callers pad (a slot of which is allocated by
525 The CvPADLIST AV has does not have AvREAL set, so REFCNT of component items
526 is managed "manual" (mostly in pad.c) rather than normal av.c rules.
527 The items in the AV are not SVs as for a normal AV, but other AVs:
529 0'th Entry of the CvPADLIST is an AV which represents the "names" or rather
530 the "static type information" for lexicals.
532 The CvDEPTH'th entry of CvPADLIST AV is an AV which is the stack frame at that
533 depth of recursion into the CV.
534 The 0'th slot of a frame AV is an AV which is @_.
535 other entries are storage for variables and op targets.
538 C<PL_comppad_name> is set to the names AV.
539 C<PL_comppad> is set to the frame AV for the frame CvDEPTH == 1.
540 C<PL_curpad> is set to the body of the frame AV (i.e. AvARRAY(PL_comppad)).
542 During execution, C<PL_comppad> and C<PL_curpad> refer to the live
543 frame of the currently executing sub.
545 Iterating over the names AV iterates over all possible pad
546 items. Pad slots that are SVs_PADTMP (targets/GVs/constants) end up having
547 &PL_sv_undef "names" (see pad_alloc()).
549 Only my/our variable (SVs_PADMY/SVs_PADOUR) slots get valid names.
550 The rest are op targets/GVs/constants which are statically allocated
551 or resolved at compile time. These don't have names by which they
552 can be looked up from Perl code at run time through eval"" like
553 my/our variables can be. Since they can't be looked up by "name"
554 but only by their index allocated at compile time (which is usually
555 in PL_op->op_targ), wasting a name SV for them doesn't make sense.
557 The SVs in the names AV have their PV being the name of the variable.
558 xlow+1..xhigh inclusive in the NV union is a range of cop_seq numbers for
559 which the name is valid. For typed lexicals name SV is SVt_PVMG and SvSTASH
560 points at the type. For C<our> lexicals, the type is also SVt_PVMG, with the
561 SvOURSTASH slot pointing at the stash of the associated global (so that
562 duplicate C<our> declarations in the same package can be detected). SvUVX is
563 sometimes hijacked to store the generation number during compilation.
565 If SvFAKE is set on the name SV, then that slot in the frame AV is
566 a REFCNT'ed reference to a lexical from "outside". In this case,
567 the name SV does not use xlow and xhigh to store a cop_seq range, since it is
568 in scope throughout. Instead xhigh stores some flags containing info about
569 the real lexical (is it declared in an anon, and is it capable of being
570 instantiated multiple times?), and for fake ANONs, xlow contains the index
571 within the parent's pad where the lexical's value is stored, to make
574 If the 'name' is '&' the corresponding entry in frame AV
575 is a CV representing a possible closure.
576 (SvFAKE and name of '&' is not a meaningful combination currently but could
577 become so if C<my sub foo {}> is implemented.)
579 Note that formats are treated as anon subs, and are cloned each time
580 write is called (if necessary).
582 The flag SVf_PADSTALE is cleared on lexicals each time the my() is executed,
583 and set on scope exit. This allows the 'Variable $x is not available' warning
584 to be generated in evals, such as
586 { my $x = 1; sub f { eval '$x'} } f();
588 For state vars, SVf_PADSTALE is overloaded to mean 'not yet initialised'
590 AV * CvPADLIST(CV *cv)
598 Clone a CV: make a new CV which points to the same code etc, but which
599 has a newly-created pad built by copying the prototype pad and capturing
602 CV* cv_clone(CV* proto)
610 dump the contents of a CV
612 void cv_dump(const CV *cv, const char *title)
620 Dump the contents of a padlist
622 void do_dump_pad(I32 level, PerlIO *file, PADLIST *padlist, int full)
630 "Introduce" my variables to visible status.
640 Add an anon code entry to the current compiling pad
642 PADOFFSET pad_add_anon(SV* sv, OPCODE op_type)
650 Create a new name and associated PADMY SV in the current pad; return the
652 If C<typestash> is valid, the name is for a typed lexical; set the
653 name's stash to that value.
654 If C<ourstash> is valid, it's an our lexical, set the name's
655 SvOURSTASH to that value
657 If fake, it means we're cloning an existing entry
659 PADOFFSET pad_add_name(const char *name, HV* typestash, HV* ourstash, bool clone, bool state)
667 Allocate a new my or tmp pad entry. For a my, simply push a null SV onto
668 the end of PL_comppad, but for a tmp, scan the pad from PL_padix upwards
669 for a slot which has no name and no active value.
671 PADOFFSET pad_alloc(I32 optype, U32 tmptype)
676 =item pad_block_start
679 Update the pad compilation state variables on entry to a new block
681 void pad_block_start(int full)
689 Check for duplicate declarations: report any of:
690 * a my in the current scope with the same name;
691 * an our (anywhere in the pad) with the same name and the same stash
693 C<is_our> indicates that the name to check is an 'our' declaration
695 void pad_check_dup(const char* name, bool is_our, const HV* ourstash)
703 Find a named lexical anywhere in a chain of nested pads. Add fake entries
704 in the inner pads if it's found in an outer one.
706 Returns the offset in the bottom pad of the lex or the fake lex.
707 cv is the CV in which to start the search, and seq is the current cop_seq
708 to match against. If warn is true, print appropriate warnings. The out_*
709 vars return values, and so are pointers to where the returned values
710 should be stored. out_capture, if non-null, requests that the innermost
711 instance of the lexical is captured; out_name_sv is set to the innermost
712 matched namesv or fake namesv; out_flags returns the flags normally
713 associated with the IVX field of a fake namesv.
715 Note that pad_findlex() is recursive; it recurses up the chain of CVs,
716 then comes back down, adding fake entries as it goes. It has to be this way
717 because fake namesvs in anon protoypes have to store in xlow the index into
720 PADOFFSET pad_findlex(const char *name, const CV* cv, U32 seq, int warn, SV** out_capture, SV** out_name_sv, int *out_flags)
728 Given a lexical name, try to find its offset, first in the current pad,
729 or failing that, in the pads of any lexically enclosing subs (including
730 the complications introduced by eval). If the name is found in an outer pad,
731 then a fake entry is added to the current pad.
732 Returns the offset in the current pad, or NOT_IN_PAD on failure.
734 PADOFFSET pad_findmy(const char* name)
739 =item pad_fixup_inner_anons
740 X<pad_fixup_inner_anons>
742 For any anon CVs in the pad, change CvOUTSIDE of that CV from
743 old_cv to new_cv if necessary. Needed when a newly-compiled CV has to be
744 moved to a pre-existing CV struct.
746 void pad_fixup_inner_anons(PADLIST *padlist, CV *old_cv, CV *new_cv)
754 Free the SV at offset po in the current pad.
756 void pad_free(PADOFFSET po)
764 Cleanup at end of scope during compilation: set the max seq number for
765 lexicals in this scope and warn of any lexicals that never got introduced.
775 Create a new compiling padlist, saving and updating the various global
776 vars at the same time as creating the pad itself. The following flags
777 can be OR'ed together:
779 padnew_CLONE this pad is for a cloned CV
780 padnew_SAVE save old globals
781 padnew_SAVESUB also save extra stuff for start of sub
783 PADLIST* pad_new(int flags)
791 Push a new pad frame onto the padlist, unless there's already a pad at
792 this depth, in which case don't bother creating a new one. Then give
793 the new pad an @_ in slot zero.
795 void pad_push(PADLIST *padlist, int depth)
803 Mark all the current temporaries for reuse
813 Set the entry at offset po in the current pad to sv.
814 Use the macro PAD_SETSV() rather than calling this function directly.
816 void pad_setsv(PADOFFSET po, SV* sv)
824 Abandon the tmp in the current pad at offset po and replace with a
827 void pad_swipe(PADOFFSET po, bool refadjust)
835 Tidy up a pad after we've finished compiling it:
836 * remove most stuff from the pads of anonsub prototypes;
840 void pad_tidy(padtidy_type type)
848 Free the padlist associated with a CV.
849 If parts of it happen to be current, we null the relevant
850 PL_*pad* global vars so that we don't have any dangling references left.
851 We also repoint the CvOUTSIDE of any about-to-be-orphaned
852 inner subs to the outer of this cv.
854 (This function should really be called pad_free, but the name was already
857 void pad_undef(CV* cv)
865 =head1 Per-Interpreter Variables
872 When Perl is run in debugging mode, with the B<-d> switch, this SV is a
873 boolean which indicates whether subs are being single-stepped.
874 Single-stepping is automatically turned on after every step. This is the C
875 variable which corresponds to Perl's $DB::single variable. See
881 Found in file intrpvar.h
886 When Perl is run in debugging mode, with the B<-d> switch, this GV contains
887 the SV which holds the name of the sub being debugged. This is the C
888 variable which corresponds to Perl's $DB::sub variable. See
894 Found in file intrpvar.h
899 Trace variable used when Perl is run in debugging mode, with the B<-d>
900 switch. This is the C variable which corresponds to Perl's $DB::trace
901 variable. See C<PL_DBsingle>.
906 Found in file intrpvar.h
911 The C variable which corresponds to Perl's $^W warning variable.
916 Found in file intrpvar.h
921 The GV which was last used for a filehandle input operation. (C<< <FH> >>)
926 Found in file intrpvar.h
931 The glob containing the output field separator - C<*,> in Perl space.
936 Found in file intrpvar.h
941 The input record separator - C<$/> in Perl space.
946 Found in file intrpvar.h
951 =head1 Stack Manipulation Macros
958 Declare Just C<SP>. This is actually identical to C<dSP>, and declares
959 a local copy of perl's stack pointer, available via the C<SP> macro.
960 See C<SP>. (Available for backward source code compatibility with the
961 old (Perl 5.005) thread model.)
971 True if this op will be the return value of an lvalue subroutine
979 =head1 SV Manipulation Functions
986 Given a chunk of memory, link it to the head of the list of arenas,
987 and split it into a list of free SVs.
989 void sv_add_arena(char *const ptr, const U32 size, const U32 flags)
997 Decrement the refcnt of each remaining SV, possibly triggering a
998 cleanup. This function may have to be called multiple times to free
999 SVs which are in complex self-referential hierarchies.
1009 Attempt to destroy all objects not yet freed
1011 void sv_clean_objs()
1016 =item sv_free_arenas
1019 Deallocate the memory used by all arenas. Note that all the individual SV
1020 heads and bodies within the arenas must already have been freed.
1022 void sv_free_arenas()
1030 =head1 SV-Body Allocation
1037 Return an SV with the numeric value of the source SV, doing any necessary
1038 reference or overload conversion. You must use the C<SvNUM(sv)> macro to
1039 access this function.
1041 SV* sv_2num(SV *const sv)
1049 =head1 Unicode Support
1053 =item find_uninit_var
1056 Find the name of the undefined variable (if any) that caused the operator o
1057 to issue a "Use of uninitialized value" warning.
1058 If match is true, only return a name if it's value matches uninit_sv.
1059 So roughly speaking, if a unary operator (such as OP_COS) generates a
1060 warning, then following the direct child of the op may yield an
1061 OP_PADSV or OP_GV that gives the name of the undefined variable. On the
1062 other hand, with OP_ADD there are two branches to follow, so we only print
1063 the variable name if we get an exact match.
1065 The name is returned as a mortal SV.
1067 Assumes that PL_op is the op that originally triggered the error, and that
1068 PL_comppad/PL_curpad points to the currently executing pad.
1070 SV* find_uninit_var(const OP *const obase, const SV *const uninit_sv, bool top)
1078 Print appropriate "Use of uninitialized variable" warning
1080 void report_uninit(const SV *uninit_sv)
1090 The autodocumentation system was originally added to the Perl core by
1091 Benjamin Stuhl. Documentation is by whoever was kind enough to
1092 document their functions.
1096 perlguts(1), perlapi(1)
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