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 *tmpglob, IO *io)
432 =head1 Magical Functions
436 =item magic_clearhint
439 Triggered by a delete from %^H, records the key to
440 C<PL_compiling.cop_hints_hash>.
442 int magic_clearhint(SV* sv, MAGIC* mg)
450 Triggered by a store to %^H, records the key/value pair to
451 C<PL_compiling.cop_hints_hash>. It is assumed that hints aren't storing
452 anything that would need a deep copy. Maybe we should warn if we find a
455 int magic_sethint(SV* sv, MAGIC* mg)
463 Copy some of the magic from an existing SV to new localized version of
464 that SV. Container magic (eg %ENV, $1, tie) gets copied, value magic
465 doesn't (eg taint, pos).
467 void mg_localize(SV* sv, SV* nsv)
479 =item mro_get_linear_isa_c3
480 X<mro_get_linear_isa_c3>
482 Returns the C3 linearization of @ISA
483 the given stash. The return value is a read-only AV*.
484 C<level> should be 0 (it is used internally in this
485 function's recursion).
487 You are responsible for C<SvREFCNT_inc()> on the
488 return value if you plan to store it anywhere
489 semi-permanently (otherwise it might be deleted
490 out from under you the next time the cache is
493 AV* mro_get_linear_isa_c3(HV* stash, I32 level)
498 =item mro_get_linear_isa_dfs
499 X<mro_get_linear_isa_dfs>
501 Returns the Depth-First Search linearization of @ISA
502 the given stash. The return value is a read-only AV*.
503 C<level> should be 0 (it is used internally in this
504 function's recursion).
506 You are responsible for C<SvREFCNT_inc()> on the
507 return value if you plan to store it anywhere
508 semi-permanently (otherwise it might be deleted
509 out from under you the next time the cache is
512 AV* mro_get_linear_isa_dfs(HV* stash, I32 level)
517 =item mro_isa_changed_in
518 X<mro_isa_changed_in>
520 Takes the necessary steps (cache invalidations, mostly)
521 when the @ISA of the given package has changed. Invoked
522 by the C<setisa> magic, should not need to invoke directly.
524 void mro_isa_changed_in(HV* stash)
532 =head1 Pad Data Structures
539 CV's can have CvPADLIST(cv) set to point to an AV.
541 For these purposes "forms" are a kind-of CV, eval""s are too (except they're
542 not callable at will and are always thrown away after the eval"" is done
543 executing). Require'd files are simply evals without any outer lexical
546 XSUBs don't have CvPADLIST set - dXSTARG fetches values from PL_curpad,
547 but that is really the callers pad (a slot of which is allocated by
550 The CvPADLIST AV has does not have AvREAL set, so REFCNT of component items
551 is managed "manual" (mostly in pad.c) rather than normal av.c rules.
552 The items in the AV are not SVs as for a normal AV, but other AVs:
554 0'th Entry of the CvPADLIST is an AV which represents the "names" or rather
555 the "static type information" for lexicals.
557 The CvDEPTH'th entry of CvPADLIST AV is an AV which is the stack frame at that
558 depth of recursion into the CV.
559 The 0'th slot of a frame AV is an AV which is @_.
560 other entries are storage for variables and op targets.
563 C<PL_comppad_name> is set to the names AV.
564 C<PL_comppad> is set to the frame AV for the frame CvDEPTH == 1.
565 C<PL_curpad> is set to the body of the frame AV (i.e. AvARRAY(PL_comppad)).
567 During execution, C<PL_comppad> and C<PL_curpad> refer to the live
568 frame of the currently executing sub.
570 Iterating over the names AV iterates over all possible pad
571 items. Pad slots that are SVs_PADTMP (targets/GVs/constants) end up having
572 &PL_sv_undef "names" (see pad_alloc()).
574 Only my/our variable (SVs_PADMY/SVs_PADOUR) slots get valid names.
575 The rest are op targets/GVs/constants which are statically allocated
576 or resolved at compile time. These don't have names by which they
577 can be looked up from Perl code at run time through eval"" like
578 my/our variables can be. Since they can't be looked up by "name"
579 but only by their index allocated at compile time (which is usually
580 in PL_op->op_targ), wasting a name SV for them doesn't make sense.
582 The SVs in the names AV have their PV being the name of the variable.
583 xlow+1..xhigh inclusive in the NV union is a range of cop_seq numbers for
584 which the name is valid. For typed lexicals name SV is SVt_PVMG and SvSTASH
585 points at the type. For C<our> lexicals, the type is also SVt_PVMG, with the
586 SvOURSTASH slot pointing at the stash of the associated global (so that
587 duplicate C<our> declarations in the same package can be detected). SvUVX is
588 sometimes hijacked to store the generation number during compilation.
590 If SvFAKE is set on the name SV, then that slot in the frame AV is
591 a REFCNT'ed reference to a lexical from "outside". In this case,
592 the name SV does not use xlow and xhigh to store a cop_seq range, since it is
593 in scope throughout. Instead xhigh stores some flags containing info about
594 the real lexical (is it declared in an anon, and is it capable of being
595 instantiated multiple times?), and for fake ANONs, xlow contains the index
596 within the parent's pad where the lexical's value is stored, to make
599 If the 'name' is '&' the corresponding entry in frame AV
600 is a CV representing a possible closure.
601 (SvFAKE and name of '&' is not a meaningful combination currently but could
602 become so if C<my sub foo {}> is implemented.)
604 Note that formats are treated as anon subs, and are cloned each time
605 write is called (if necessary).
607 The flag SVf_PADSTALE is cleared on lexicals each time the my() is executed,
608 and set on scope exit. This allows the 'Variable $x is not available' warning
609 to be generated in evals, such as
611 { my $x = 1; sub f { eval '$x'} } f();
613 For state vars, SVf_PADSTALE is overloaded to mean 'not yet initialised'
615 AV * CvPADLIST(CV *cv)
623 Clone a CV: make a new CV which points to the same code etc, but which
624 has a newly-created pad built by copying the prototype pad and capturing
627 CV* cv_clone(CV* proto)
635 dump the contents of a CV
637 void cv_dump(const CV *cv, const char *title)
645 Dump the contents of a padlist
647 void do_dump_pad(I32 level, PerlIO *file, PADLIST *padlist, int full)
655 "Introduce" my variables to visible status.
665 Add an anon code entry to the current compiling pad
667 PADOFFSET pad_add_anon(SV* sv, OPCODE op_type)
675 Create a new name and associated PADMY SV in the current pad; return the
677 If C<typestash> is valid, the name is for a typed lexical; set the
678 name's stash to that value.
679 If C<ourstash> is valid, it's an our lexical, set the name's
680 SvOURSTASH to that value
682 If fake, it means we're cloning an existing entry
684 PADOFFSET pad_add_name(const char *name, HV* typestash, HV* ourstash, bool clone, bool state)
692 Allocate a new my or tmp pad entry. For a my, simply push a null SV onto
693 the end of PL_comppad, but for a tmp, scan the pad from PL_padix upwards
694 for a slot which has no name and no active value.
696 PADOFFSET pad_alloc(I32 optype, U32 tmptype)
701 =item pad_block_start
704 Update the pad compilation state variables on entry to a new block
706 void pad_block_start(int full)
714 Check for duplicate declarations: report any of:
715 * a my in the current scope with the same name;
716 * an our (anywhere in the pad) with the same name and the same stash
718 C<is_our> indicates that the name to check is an 'our' declaration
720 void pad_check_dup(const char* name, bool is_our, const HV* ourstash)
728 Find a named lexical anywhere in a chain of nested pads. Add fake entries
729 in the inner pads if it's found in an outer one.
731 Returns the offset in the bottom pad of the lex or the fake lex.
732 cv is the CV in which to start the search, and seq is the current cop_seq
733 to match against. If warn is true, print appropriate warnings. The out_*
734 vars return values, and so are pointers to where the returned values
735 should be stored. out_capture, if non-null, requests that the innermost
736 instance of the lexical is captured; out_name_sv is set to the innermost
737 matched namesv or fake namesv; out_flags returns the flags normally
738 associated with the IVX field of a fake namesv.
740 Note that pad_findlex() is recursive; it recurses up the chain of CVs,
741 then comes back down, adding fake entries as it goes. It has to be this way
742 because fake namesvs in anon protoypes have to store in xlow the index into
745 PADOFFSET pad_findlex(const char *name, const CV* cv, U32 seq, int warn, SV** out_capture, SV** out_name_sv, int *out_flags)
753 Given a lexical name, try to find its offset, first in the current pad,
754 or failing that, in the pads of any lexically enclosing subs (including
755 the complications introduced by eval). If the name is found in an outer pad,
756 then a fake entry is added to the current pad.
757 Returns the offset in the current pad, or NOT_IN_PAD on failure.
759 PADOFFSET pad_findmy(const char* name)
764 =item pad_fixup_inner_anons
765 X<pad_fixup_inner_anons>
767 For any anon CVs in the pad, change CvOUTSIDE of that CV from
768 old_cv to new_cv if necessary. Needed when a newly-compiled CV has to be
769 moved to a pre-existing CV struct.
771 void pad_fixup_inner_anons(PADLIST *padlist, CV *old_cv, CV *new_cv)
779 Free the SV at offset po in the current pad.
781 void pad_free(PADOFFSET po)
789 Cleanup at end of scope during compilation: set the max seq number for
790 lexicals in this scope and warn of any lexicals that never got introduced.
800 Create a new compiling padlist, saving and updating the various global
801 vars at the same time as creating the pad itself. The following flags
802 can be OR'ed together:
804 padnew_CLONE this pad is for a cloned CV
805 padnew_SAVE save old globals
806 padnew_SAVESUB also save extra stuff for start of sub
808 PADLIST* pad_new(int flags)
816 Push a new pad frame onto the padlist, unless there's already a pad at
817 this depth, in which case don't bother creating a new one. Then give
818 the new pad an @_ in slot zero.
820 void pad_push(PADLIST *padlist, int depth)
828 Mark all the current temporaries for reuse
838 Set the entry at offset po in the current pad to sv.
839 Use the macro PAD_SETSV() rather than calling this function directly.
841 void pad_setsv(PADOFFSET po, SV* sv)
849 Abandon the tmp in the current pad at offset po and replace with a
852 void pad_swipe(PADOFFSET po, bool refadjust)
860 Tidy up a pad after we've finished compiling it:
861 * remove most stuff from the pads of anonsub prototypes;
865 void pad_tidy(padtidy_type type)
873 Free the padlist associated with a CV.
874 If parts of it happen to be current, we null the relevant
875 PL_*pad* global vars so that we don't have any dangling references left.
876 We also repoint the CvOUTSIDE of any about-to-be-orphaned
877 inner subs to the outer of this cv.
879 (This function should really be called pad_free, but the name was already
882 void pad_undef(CV* cv)
890 =head1 Per-Interpreter Variables
897 When Perl is run in debugging mode, with the B<-d> switch, this SV is a
898 boolean which indicates whether subs are being single-stepped.
899 Single-stepping is automatically turned on after every step. This is the C
900 variable which corresponds to Perl's $DB::single variable. See
906 Found in file intrpvar.h
911 When Perl is run in debugging mode, with the B<-d> switch, this GV contains
912 the SV which holds the name of the sub being debugged. This is the C
913 variable which corresponds to Perl's $DB::sub variable. See
919 Found in file intrpvar.h
924 Trace variable used when Perl is run in debugging mode, with the B<-d>
925 switch. This is the C variable which corresponds to Perl's $DB::trace
926 variable. See C<PL_DBsingle>.
931 Found in file intrpvar.h
936 The C variable which corresponds to Perl's $^W warning variable.
941 Found in file intrpvar.h
946 The GV which was last used for a filehandle input operation. (C<< <FH> >>)
951 Found in file intrpvar.h
956 The output field separator - C<$,> in Perl space.
961 Found in file intrpvar.h
966 The input record separator - C<$/> in Perl space.
971 Found in file intrpvar.h
976 =head1 Stack Manipulation Macros
983 Declare Just C<SP>. This is actually identical to C<dSP>, and declares
984 a local copy of perl's stack pointer, available via the C<SP> macro.
985 See C<SP>. (Available for backward source code compatibility with the
986 old (Perl 5.005) thread model.)
996 True if this op will be the return value of an lvalue subroutine
1004 =head1 SV Manipulation Functions
1011 Given a chunk of memory, link it to the head of the list of arenas,
1012 and split it into a list of free SVs.
1014 void sv_add_arena(char *const ptr, const U32 size, const U32 flags)
1022 Decrement the refcnt of each remaining SV, possibly triggering a
1023 cleanup. This function may have to be called multiple times to free
1024 SVs which are in complex self-referential hierarchies.
1034 Attempt to destroy all objects not yet freed
1036 void sv_clean_objs()
1041 =item sv_free_arenas
1044 Deallocate the memory used by all arenas. Note that all the individual SV
1045 heads and bodies within the arenas must already have been freed.
1047 void sv_free_arenas()
1055 =head1 SV-Body Allocation
1062 Return an SV with the numeric value of the source SV, doing any necessary
1063 reference or overload conversion. You must use the C<SvNUM(sv)> macro to
1064 access this function.
1066 SV* sv_2num(SV *const sv)
1074 =head1 Unicode Support
1078 =item find_uninit_var
1081 Find the name of the undefined variable (if any) that caused the operator o
1082 to issue a "Use of uninitialized value" warning.
1083 If match is true, only return a name if it's value matches uninit_sv.
1084 So roughly speaking, if a unary operator (such as OP_COS) generates a
1085 warning, then following the direct child of the op may yield an
1086 OP_PADSV or OP_GV that gives the name of the undefined variable. On the
1087 other hand, with OP_ADD there are two branches to follow, so we only print
1088 the variable name if we get an exact match.
1090 The name is returned as a mortal SV.
1092 Assumes that PL_op is the op that originally triggered the error, and that
1093 PL_comppad/PL_curpad points to the currently executing pad.
1095 SV* find_uninit_var(OP* obase, SV* uninit_sv, bool top)
1103 Print appropriate "Use of uninitialized variable" warning
1105 void report_uninit(SV* uninit_sv)
1115 The autodocumentation system was originally added to the Perl core by
1116 Benjamin Stuhl. Documentation is by whoever was kind enough to
1117 document their functions.
1121 perlguts(1), perlapi(1)