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)
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(const char *name, STRLEN len, U32 flags)
357 =item is_gv_magical_sv
360 Returns C<TRUE> if given the name of a magical GV. Calls is_gv_magical.
362 bool is_gv_magical_sv(SV *name, U32 flags)
370 =head1 Hash Manipulation Functions
374 =item refcounted_he_chain_2hv
375 X<refcounted_he_chain_2hv>
377 Generates and returns a C<HV *> by walking up the tree starting at the passed
378 in C<struct refcounted_he *>.
380 HV * refcounted_he_chain_2hv(const struct refcounted_he *c)
385 =item refcounted_he_free
386 X<refcounted_he_free>
388 Decrements the reference count of the passed in C<struct refcounted_he *>
389 by one. If the reference count reaches zero the structure's memory is freed,
390 and C<refcounted_he_free> iterates onto the parent node.
392 void refcounted_he_free(struct refcounted_he *he)
397 =item refcounted_he_new
400 Creates a new C<struct refcounted_he>. As S<key> is copied, and value is
401 stored in a compact form, all references remain the property of the caller.
402 The C<struct refcounted_he> is returned with a reference count of 1.
404 struct refcounted_he * refcounted_he_new(struct refcounted_he *const parent, SV *const key, SV *const value)
419 Function called by C<do_readline> to spawn a glob (or do the glob inside
420 perl on VMS). This code used to be inline, but now perl uses C<File::Glob>
421 this glob starter is only used by miniperl during the build process.
422 Moving it away shrinks pp_hot.c; shrinking pp_hot.c helps speed perl up.
424 PerlIO* start_glob(SV* pattern, IO *io)
432 =head1 Magical Functions
439 Triggered by a delete from %^H, records the key to
440 C<PL_compiling.cop_hints_hash>.
442 int magic_sethint(SV* sv, MAGIC* mg)
450 Copy some of the magic from an existing SV to new localized version of
451 that SV. Container magic (eg %ENV, $1, tie) gets copied, value magic
452 doesn't (eg taint, pos).
454 void mg_localize(SV* sv, SV* nsv)
466 =item mro_get_linear_isa_c3
467 X<mro_get_linear_isa_c3>
469 Returns the C3 linearization of @ISA
470 the given stash. The return value is a read-only AV*.
471 C<level> should be 0 (it is used internally in this
472 function's recursion).
474 You are responsible for C<SvREFCNT_inc()> on the
475 return value if you plan to store it anywhere
476 semi-permanently (otherwise it might be deleted
477 out from under you the next time the cache is
480 AV* mro_get_linear_isa_c3(HV* stash, I32 level)
485 =item mro_get_linear_isa_dfs
486 X<mro_get_linear_isa_dfs>
488 Returns the Depth-First Search linearization of @ISA
489 the given stash. The return value is a read-only AV*.
490 C<level> should be 0 (it is used internally in this
491 function's recursion).
493 You are responsible for C<SvREFCNT_inc()> on the
494 return value if you plan to store it anywhere
495 semi-permanently (otherwise it might be deleted
496 out from under you the next time the cache is
499 AV* mro_get_linear_isa_dfs(HV* stash, I32 level)
504 =item mro_isa_changed_in
505 X<mro_isa_changed_in>
507 Takes the necessary steps (cache invalidations, mostly)
508 when the @ISA of the given package has changed. Invoked
509 by the C<setisa> magic, should not need to invoke directly.
511 void mro_isa_changed_in(HV* stash)
519 =head1 Pad Data Structures
526 CV's can have CvPADLIST(cv) set to point to an AV.
528 For these purposes "forms" are a kind-of CV, eval""s are too (except they're
529 not callable at will and are always thrown away after the eval"" is done
530 executing). Require'd files are simply evals without any outer lexical
533 XSUBs don't have CvPADLIST set - dXSTARG fetches values from PL_curpad,
534 but that is really the callers pad (a slot of which is allocated by
537 The CvPADLIST AV has does not have AvREAL set, so REFCNT of component items
538 is managed "manual" (mostly in pad.c) rather than normal av.c rules.
539 The items in the AV are not SVs as for a normal AV, but other AVs:
541 0'th Entry of the CvPADLIST is an AV which represents the "names" or rather
542 the "static type information" for lexicals.
544 The CvDEPTH'th entry of CvPADLIST AV is an AV which is the stack frame at that
545 depth of recursion into the CV.
546 The 0'th slot of a frame AV is an AV which is @_.
547 other entries are storage for variables and op targets.
550 C<PL_comppad_name> is set to the names AV.
551 C<PL_comppad> is set to the frame AV for the frame CvDEPTH == 1.
552 C<PL_curpad> is set to the body of the frame AV (i.e. AvARRAY(PL_comppad)).
554 During execution, C<PL_comppad> and C<PL_curpad> refer to the live
555 frame of the currently executing sub.
557 Iterating over the names AV iterates over all possible pad
558 items. Pad slots that are SVs_PADTMP (targets/GVs/constants) end up having
559 &PL_sv_undef "names" (see pad_alloc()).
561 Only my/our variable (SVs_PADMY/SVs_PADOUR) slots get valid names.
562 The rest are op targets/GVs/constants which are statically allocated
563 or resolved at compile time. These don't have names by which they
564 can be looked up from Perl code at run time through eval"" like
565 my/our variables can be. Since they can't be looked up by "name"
566 but only by their index allocated at compile time (which is usually
567 in PL_op->op_targ), wasting a name SV for them doesn't make sense.
569 The SVs in the names AV have their PV being the name of the variable.
570 xlow+1..xhigh inclusive in the NV union is a range of cop_seq numbers for
571 which the name is valid. For typed lexicals name SV is SVt_PVMG and SvSTASH
572 points at the type. For C<our> lexicals, the type is also SVt_PVMG, with the
573 SvOURSTASH slot pointing at the stash of the associated global (so that
574 duplicate C<our> declarations in the same package can be detected). SvUVX is
575 sometimes hijacked to store the generation number during compilation.
577 If SvFAKE is set on the name SV, then that slot in the frame AV is
578 a REFCNT'ed reference to a lexical from "outside". In this case,
579 the name SV does not use xlow and xhigh to store a cop_seq range, since it is
580 in scope throughout. Instead xhigh stores some flags containing info about
581 the real lexical (is it declared in an anon, and is it capable of being
582 instantiated multiple times?), and for fake ANONs, xlow contains the index
583 within the parent's pad where the lexical's value is stored, to make
586 If the 'name' is '&' the corresponding entry in frame AV
587 is a CV representing a possible closure.
588 (SvFAKE and name of '&' is not a meaningful combination currently but could
589 become so if C<my sub foo {}> is implemented.)
591 Note that formats are treated as anon subs, and are cloned each time
592 write is called (if necessary).
594 The flag SVf_PADSTALE is cleared on lexicals each time the my() is executed,
595 and set on scope exit. This allows the 'Variable $x is not available' warning
596 to be generated in evals, such as
598 { my $x = 1; sub f { eval '$x'} } f();
600 For state vars, SVf_PADSTALE is overloaded to mean 'not yet initialised'
602 AV * CvPADLIST(CV *cv)
610 Clone a CV: make a new CV which points to the same code etc, but which
611 has a newly-created pad built by copying the prototype pad and capturing
614 CV* cv_clone(CV* proto)
622 dump the contents of a CV
624 void cv_dump(const CV *cv, const char *title)
632 Dump the contents of a padlist
634 void do_dump_pad(I32 level, PerlIO *file, PADLIST *padlist, int full)
642 "Introduce" my variables to visible status.
652 Add an anon code entry to the current compiling pad
654 PADOFFSET pad_add_anon(SV* sv, OPCODE op_type)
662 Create a new name and associated PADMY SV in the current pad; return the
664 If C<typestash> is valid, the name is for a typed lexical; set the
665 name's stash to that value.
666 If C<ourstash> is valid, it's an our lexical, set the name's
667 SvOURSTASH to that value
669 If fake, it means we're cloning an existing entry
671 PADOFFSET pad_add_name(const char *name, HV* typestash, HV* ourstash, bool clone, bool state)
679 Allocate a new my or tmp pad entry. For a my, simply push a null SV onto
680 the end of PL_comppad, but for a tmp, scan the pad from PL_padix upwards
681 for a slot which has no name and no active value.
683 PADOFFSET pad_alloc(I32 optype, U32 tmptype)
688 =item pad_block_start
691 Update the pad compilation state variables on entry to a new block
693 void pad_block_start(int full)
701 Check for duplicate declarations: report any of:
702 * a my in the current scope with the same name;
703 * an our (anywhere in the pad) with the same name and the same stash
705 C<is_our> indicates that the name to check is an 'our' declaration
707 void pad_check_dup(const char* name, bool is_our, const HV* ourstash)
715 Find a named lexical anywhere in a chain of nested pads. Add fake entries
716 in the inner pads if it's found in an outer one.
718 Returns the offset in the bottom pad of the lex or the fake lex.
719 cv is the CV in which to start the search, and seq is the current cop_seq
720 to match against. If warn is true, print appropriate warnings. The out_*
721 vars return values, and so are pointers to where the returned values
722 should be stored. out_capture, if non-null, requests that the innermost
723 instance of the lexical is captured; out_name_sv is set to the innermost
724 matched namesv or fake namesv; out_flags returns the flags normally
725 associated with the IVX field of a fake namesv.
727 Note that pad_findlex() is recursive; it recurses up the chain of CVs,
728 then comes back down, adding fake entries as it goes. It has to be this way
729 because fake namesvs in anon protoypes have to store in xlow the index into
732 PADOFFSET pad_findlex(const char *name, const CV* cv, U32 seq, int warn, SV** out_capture, SV** out_name_sv, int *out_flags)
740 Given a lexical name, try to find its offset, first in the current pad,
741 or failing that, in the pads of any lexically enclosing subs (including
742 the complications introduced by eval). If the name is found in an outer pad,
743 then a fake entry is added to the current pad.
744 Returns the offset in the current pad, or NOT_IN_PAD on failure.
746 PADOFFSET pad_findmy(const char* name)
751 =item pad_fixup_inner_anons
752 X<pad_fixup_inner_anons>
754 For any anon CVs in the pad, change CvOUTSIDE of that CV from
755 old_cv to new_cv if necessary. Needed when a newly-compiled CV has to be
756 moved to a pre-existing CV struct.
758 void pad_fixup_inner_anons(PADLIST *padlist, CV *old_cv, CV *new_cv)
766 Free the SV at offset po in the current pad.
768 void pad_free(PADOFFSET po)
776 Cleanup at end of scope during compilation: set the max seq number for
777 lexicals in this scope and warn of any lexicals that never got introduced.
787 Create a new compiling padlist, saving and updating the various global
788 vars at the same time as creating the pad itself. The following flags
789 can be OR'ed together:
791 padnew_CLONE this pad is for a cloned CV
792 padnew_SAVE save old globals
793 padnew_SAVESUB also save extra stuff for start of sub
795 PADLIST* pad_new(int flags)
803 Push a new pad frame onto the padlist, unless there's already a pad at
804 this depth, in which case don't bother creating a new one. Then give
805 the new pad an @_ in slot zero.
807 void pad_push(PADLIST *padlist, int depth)
815 Mark all the current temporaries for reuse
825 Set the entry at offset po in the current pad to sv.
826 Use the macro PAD_SETSV() rather than calling this function directly.
828 void pad_setsv(PADOFFSET po, SV* sv)
836 Abandon the tmp in the current pad at offset po and replace with a
839 void pad_swipe(PADOFFSET po, bool refadjust)
847 Tidy up a pad after we've finished compiling it:
848 * remove most stuff from the pads of anonsub prototypes;
852 void pad_tidy(padtidy_type type)
860 Free the padlist associated with a CV.
861 If parts of it happen to be current, we null the relevant
862 PL_*pad* global vars so that we don't have any dangling references left.
863 We also repoint the CvOUTSIDE of any about-to-be-orphaned
864 inner subs to the outer of this cv.
866 (This function should really be called pad_free, but the name was already
869 void pad_undef(CV* cv)
877 =head1 Per-Interpreter Variables
884 When Perl is run in debugging mode, with the B<-d> switch, this SV is a
885 boolean which indicates whether subs are being single-stepped.
886 Single-stepping is automatically turned on after every step. This is the C
887 variable which corresponds to Perl's $DB::single variable. See
893 Found in file intrpvar.h
898 When Perl is run in debugging mode, with the B<-d> switch, this GV contains
899 the SV which holds the name of the sub being debugged. This is the C
900 variable which corresponds to Perl's $DB::sub variable. See
906 Found in file intrpvar.h
911 Trace variable used when Perl is run in debugging mode, with the B<-d>
912 switch. This is the C variable which corresponds to Perl's $DB::trace
913 variable. See C<PL_DBsingle>.
918 Found in file intrpvar.h
923 The C variable which corresponds to Perl's $^W warning variable.
928 Found in file intrpvar.h
933 The GV which was last used for a filehandle input operation. (C<< <FH> >>)
938 Found in file intrpvar.h
943 The output field separator - C<$,> in Perl space.
948 Found in file intrpvar.h
953 The input record separator - C<$/> in Perl space.
958 Found in file intrpvar.h
963 =head1 Stack Manipulation Macros
970 Declare Just C<SP>. This is actually identical to C<dSP>, and declares
971 a local copy of perl's stack pointer, available via the C<SP> macro.
972 See C<SP>. (Available for backward source code compatibility with the
973 old (Perl 5.005) thread model.)
983 True if this op will be the return value of an lvalue subroutine
991 =head1 SV Manipulation Functions
998 Given a chunk of memory, link it to the head of the list of arenas,
999 and split it into a list of free SVs.
1001 void sv_add_arena(char *const ptr, const U32 size, const U32 flags)
1009 Decrement the refcnt of each remaining SV, possibly triggering a
1010 cleanup. This function may have to be called multiple times to free
1011 SVs which are in complex self-referential hierarchies.
1021 Attempt to destroy all objects not yet freed
1023 void sv_clean_objs()
1028 =item sv_free_arenas
1031 Deallocate the memory used by all arenas. Note that all the individual SV
1032 heads and bodies within the arenas must already have been freed.
1034 void sv_free_arenas()
1042 =head1 SV-Body Allocation
1049 Return an SV with the numeric value of the source SV, doing any necessary
1050 reference or overload conversion. You must use the C<SvNUM(sv)> macro to
1051 access this function.
1053 SV* sv_2num(SV *const sv)
1061 =head1 Unicode Support
1065 =item find_uninit_var
1068 Find the name of the undefined variable (if any) that caused the operator o
1069 to issue a "Use of uninitialized value" warning.
1070 If match is true, only return a name if it's value matches uninit_sv.
1071 So roughly speaking, if a unary operator (such as OP_COS) generates a
1072 warning, then following the direct child of the op may yield an
1073 OP_PADSV or OP_GV that gives the name of the undefined variable. On the
1074 other hand, with OP_ADD there are two branches to follow, so we only print
1075 the variable name if we get an exact match.
1077 The name is returned as a mortal SV.
1079 Assumes that PL_op is the op that originally triggered the error, and that
1080 PL_comppad/PL_curpad points to the currently executing pad.
1082 SV* find_uninit_var(OP* obase, SV* uninit_sv, bool top)
1090 Print appropriate "Use of uninitialized variable" warning
1092 void report_uninit(SV* uninit_sv)
1102 The autodocumentation system was originally added to the Perl core by
1103 Benjamin Stuhl. Documentation is by whoever was kind enough to
1104 document their functions.
1108 perlguts(1), perlapi(1)
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