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)
123 Clone the state variables associated with running and compiling pads.
125 void PAD_CLONE_VARS(PerlInterpreter *proto_perl \)
130 =item PAD_COMPNAME_FLAGS
131 X<PAD_COMPNAME_FLAGS>
133 Return the flags for the current compiling pad name
134 at offset C<po>. Assumes a valid slot entry.
136 U32 PAD_COMPNAME_FLAGS(PADOFFSET po)
141 =item PAD_COMPNAME_GEN
144 The generation number of the name at offset C<po> in the current
145 compiling pad (lvalue). Note that C<SvUVX> is hijacked for this purpose.
147 STRLEN PAD_COMPNAME_GEN(PADOFFSET po)
152 =item PAD_COMPNAME_GEN_set
153 X<PAD_COMPNAME_GEN_set>
155 Sets the generation number of the name at offset C<po> in the current
156 ling pad (lvalue) to C<gen>. Note that C<SvUV_set> is hijacked for this purpose.
158 STRLEN PAD_COMPNAME_GEN_set(PADOFFSET po, int gen)
163 =item PAD_COMPNAME_OURSTASH
164 X<PAD_COMPNAME_OURSTASH>
166 Return the stash associated with an C<our> variable.
167 Assumes the slot entry is a valid C<our> lexical.
169 HV * PAD_COMPNAME_OURSTASH(PADOFFSET po)
174 =item PAD_COMPNAME_PV
177 Return the name of the current compiling pad name
178 at offset C<po>. Assumes a valid slot entry.
180 char * PAD_COMPNAME_PV(PADOFFSET po)
185 =item PAD_COMPNAME_TYPE
188 Return the type (stash) of the current compiling pad name at offset
189 C<po>. Must be a valid name. Returns null if not typed.
191 HV * PAD_COMPNAME_TYPE(PADOFFSET po)
201 void PAD_DUP(PADLIST dstpad, PADLIST srcpad, CLONE_PARAMS* param)
206 =item PAD_RESTORE_LOCAL
209 Restore the old pad saved into the local variable opad by PAD_SAVE_LOCAL()
211 void PAD_RESTORE_LOCAL(PAD *opad)
219 Save the current pad to the local variable opad, then make the
220 current pad equal to npad
222 void PAD_SAVE_LOCAL(PAD *opad, PAD *npad)
227 =item PAD_SAVE_SETNULLPAD
228 X<PAD_SAVE_SETNULLPAD>
230 Save the current pad then set it to null.
232 void PAD_SAVE_SETNULLPAD()
240 Set the slot at offset C<po> in the current pad to C<sv>
242 SV * PAD_SETSV(PADOFFSET po, SV* sv)
250 Set the current pad to be pad C<n> in the padlist, saving
251 the previous current pad. NB currently this macro expands to a string too
252 long for some compilers, so it's best to replace it with
255 PAD_SET_CUR_NOSAVE(padlist,n);
258 void PAD_SET_CUR(PADLIST padlist, I32 n)
263 =item PAD_SET_CUR_NOSAVE
264 X<PAD_SET_CUR_NOSAVE>
266 like PAD_SET_CUR, but without the save
268 void PAD_SET_CUR_NOSAVE(PADLIST padlist, I32 n)
276 Get the value at offset C<po> in the current pad
278 void PAD_SV(PADOFFSET po)
286 Lightweight and lvalue version of C<PAD_SV>.
287 Get or set the value at offset C<po> in the current pad.
288 Unlike C<PAD_SV>, does not print diagnostics with -DX.
289 For internal use only.
291 SV * PAD_SVl(PADOFFSET po)
299 Clear the pointed to pad value on scope exit. (i.e. the runtime action of 'my')
301 void SAVECLEARSV(SV **svp)
309 save PL_comppad and PL_curpad
323 Save a pad slot (used to restore after an iteration)
325 XXX DAPM it would make more sense to make the arg a PADOFFSET
326 void SAVEPADSV(PADOFFSET po)
334 =head1 Functions in file pp_ctl.c
342 Locate the CV corresponding to the currently executing sub or eval.
343 If db_seqp is non_null, skip CVs that are in the DB package and populate
344 *db_seqp with the cop sequence number at the point that the DB:: code was
345 entered. (allows debuggers to eval in the scope of the breakpoint rather
346 than in the scope of the debugger itself).
348 CV* find_runcv(U32 *db_seqp)
351 Found in file pp_ctl.c
363 Returns C<TRUE> if given the name of a magical GV.
365 Currently only useful internally when determining if a GV should be
366 created even in rvalue contexts.
368 C<flags> is not used at present but available for future extension to
369 allow selecting particular classes of magical variable.
371 Currently assumes that C<name> is NUL terminated (as well as len being valid).
372 This assumption is met by all callers within the perl core, which all pass
373 pointers returned by SvPV.
375 bool is_gv_magical(const char *name, STRLEN len, U32 flags)
380 =item is_gv_magical_sv
383 Returns C<TRUE> if given the name of a magical GV. Calls is_gv_magical.
385 bool is_gv_magical_sv(SV *name, U32 flags)
393 =head1 Hash Manipulation Functions
397 =item refcounted_he_chain_2hv
398 X<refcounted_he_chain_2hv>
400 Generates and returns a C<HV *> by walking up the tree starting at the passed
401 in C<struct refcounted_he *>.
403 HV * refcounted_he_chain_2hv(const struct refcounted_he *c)
408 =item refcounted_he_free
409 X<refcounted_he_free>
411 Decrements the reference count of the passed in C<struct refcounted_he *>
412 by one. If the reference count reaches zero the structure's memory is freed,
413 and C<refcounted_he_free> iterates onto the parent node.
415 void refcounted_he_free(struct refcounted_he *he)
420 =item refcounted_he_new
423 Creates a new C<struct refcounted_he>. As S<key> is copied, and value is
424 stored in a compact form, all references remain the property of the caller.
425 The C<struct refcounted_he> is returned with a reference count of 1.
427 struct refcounted_he * refcounted_he_new(struct refcounted_he *const parent, SV *const key, SV *const value)
442 Function called by C<do_readline> to spawn a glob (or do the glob inside
443 perl on VMS). This code used to be inline, but now perl uses C<File::Glob>
444 this glob starter is only used by miniperl during the build process.
445 Moving it away shrinks pp_hot.c; shrinking pp_hot.c helps speed perl up.
447 PerlIO* start_glob(SV* pattern, IO *io)
455 =head1 Magical Functions
462 Triggered by a delete from %^H, records the key to
463 C<PL_compiling.cop_hints_hash>.
465 int magic_sethint(SV* sv, MAGIC* mg)
473 Copy some of the magic from an existing SV to new localized version of
474 that SV. Container magic (eg %ENV, $1, tie) gets copied, value magic
475 doesn't (eg taint, pos).
477 void mg_localize(SV* sv, SV* nsv)
489 =item mro_isa_changed_in
490 X<mro_isa_changed_in>
492 Takes the necessary steps (cache invalidations, mostly)
493 when the @ISA of the given package has changed. Invoked
494 by the C<setisa> magic, should not need to invoke directly.
496 void mro_isa_changed_in(HV* stash)
504 =head1 Pad Data Structures
511 CV's can have CvPADLIST(cv) set to point to an AV.
513 For these purposes "forms" are a kind-of CV, eval""s are too (except they're
514 not callable at will and are always thrown away after the eval"" is done
515 executing). Require'd files are simply evals without any outer lexical
518 XSUBs don't have CvPADLIST set - dXSTARG fetches values from PL_curpad,
519 but that is really the callers pad (a slot of which is allocated by
522 The CvPADLIST AV has does not have AvREAL set, so REFCNT of component items
523 is managed "manual" (mostly in pad.c) rather than normal av.c rules.
524 The items in the AV are not SVs as for a normal AV, but other AVs:
526 0'th Entry of the CvPADLIST is an AV which represents the "names" or rather
527 the "static type information" for lexicals.
529 The CvDEPTH'th entry of CvPADLIST AV is an AV which is the stack frame at that
530 depth of recursion into the CV.
531 The 0'th slot of a frame AV is an AV which is @_.
532 other entries are storage for variables and op targets.
535 C<PL_comppad_name> is set to the names AV.
536 C<PL_comppad> is set to the frame AV for the frame CvDEPTH == 1.
537 C<PL_curpad> is set to the body of the frame AV (i.e. AvARRAY(PL_comppad)).
539 During execution, C<PL_comppad> and C<PL_curpad> refer to the live
540 frame of the currently executing sub.
542 Iterating over the names AV iterates over all possible pad
543 items. Pad slots that are SVs_PADTMP (targets/GVs/constants) end up having
544 &PL_sv_undef "names" (see pad_alloc()).
546 Only my/our variable (SVs_PADMY/SVs_PADOUR) slots get valid names.
547 The rest are op targets/GVs/constants which are statically allocated
548 or resolved at compile time. These don't have names by which they
549 can be looked up from Perl code at run time through eval"" like
550 my/our variables can be. Since they can't be looked up by "name"
551 but only by their index allocated at compile time (which is usually
552 in PL_op->op_targ), wasting a name SV for them doesn't make sense.
554 The SVs in the names AV have their PV being the name of the variable.
555 xlow+1..xhigh inclusive in the NV union is a range of cop_seq numbers for
556 which the name is valid. For typed lexicals name SV is SVt_PVMG and SvSTASH
557 points at the type. For C<our> lexicals, the type is also SVt_PVMG, with the
558 SvOURSTASH slot pointing at the stash of the associated global (so that
559 duplicate C<our> declarations in the same package can be detected). SvUVX is
560 sometimes hijacked to store the generation number during compilation.
562 If SvFAKE is set on the name SV, then that slot in the frame AV is
563 a REFCNT'ed reference to a lexical from "outside". In this case,
564 the name SV does not use xlow and xhigh to store a cop_seq range, since it is
565 in scope throughout. Instead xhigh stores some flags containing info about
566 the real lexical (is it declared in an anon, and is it capable of being
567 instantiated multiple times?), and for fake ANONs, xlow contains the index
568 within the parent's pad where the lexical's value is stored, to make
571 If the 'name' is '&' the corresponding entry in frame AV
572 is a CV representing a possible closure.
573 (SvFAKE and name of '&' is not a meaningful combination currently but could
574 become so if C<my sub foo {}> is implemented.)
576 Note that formats are treated as anon subs, and are cloned each time
577 write is called (if necessary).
579 The flag SVf_PADSTALE is cleared on lexicals each time the my() is executed,
580 and set on scope exit. This allows the 'Variable $x is not available' warning
581 to be generated in evals, such as
583 { my $x = 1; sub f { eval '$x'} } f();
585 AV * CvPADLIST(CV *cv)
593 Clone a CV: make a new CV which points to the same code etc, but which
594 has a newly-created pad built by copying the prototype pad and capturing
597 CV* cv_clone(CV* proto)
605 dump the contents of a CV
607 void cv_dump(const CV *cv, const char *title)
615 Dump the contents of a padlist
617 void do_dump_pad(I32 level, PerlIO *file, PADLIST *padlist, int full)
625 "Introduce" my variables to visible status.
635 Add an anon code entry to the current compiling pad
637 PADOFFSET pad_add_anon(SV* sv, OPCODE op_type)
645 Create a new name and associated PADMY SV in the current pad; return the
647 If C<typestash> is valid, the name is for a typed lexical; set the
648 name's stash to that value.
649 If C<ourstash> is valid, it's an our lexical, set the name's
650 SvOURSTASH to that value
652 If fake, it means we're cloning an existing entry
654 PADOFFSET pad_add_name(const char *name, HV* typestash, HV* ourstash, bool clone, bool state)
662 Allocate a new my or tmp pad entry. For a my, simply push a null SV onto
663 the end of PL_comppad, but for a tmp, scan the pad from PL_padix upwards
664 for a slot which has no name and no active value.
666 PADOFFSET pad_alloc(I32 optype, U32 tmptype)
671 =item pad_block_start
674 Update the pad compilation state variables on entry to a new block
676 void pad_block_start(int full)
684 Check for duplicate declarations: report any of:
685 * a my in the current scope with the same name;
686 * an our (anywhere in the pad) with the same name and the same stash
688 C<is_our> indicates that the name to check is an 'our' declaration
690 void pad_check_dup(const char* name, bool is_our, const HV* ourstash)
698 Find a named lexical anywhere in a chain of nested pads. Add fake entries
699 in the inner pads if it's found in an outer one.
701 Returns the offset in the bottom pad of the lex or the fake lex.
702 cv is the CV in which to start the search, and seq is the current cop_seq
703 to match against. If warn is true, print appropriate warnings. The out_*
704 vars return values, and so are pointers to where the returned values
705 should be stored. out_capture, if non-null, requests that the innermost
706 instance of the lexical is captured; out_name_sv is set to the innermost
707 matched namesv or fake namesv; out_flags returns the flags normally
708 associated with the IVX field of a fake namesv.
710 Note that pad_findlex() is recursive; it recurses up the chain of CVs,
711 then comes back down, adding fake entries as it goes. It has to be this way
712 because fake namesvs in anon protoypes have to store in xlow the index into
715 PADOFFSET pad_findlex(const char *name, const CV* cv, U32 seq, int warn, SV** out_capture, SV** out_name_sv, int *out_flags)
723 Given a lexical name, try to find its offset, first in the current pad,
724 or failing that, in the pads of any lexically enclosing subs (including
725 the complications introduced by eval). If the name is found in an outer pad,
726 then a fake entry is added to the current pad.
727 Returns the offset in the current pad, or NOT_IN_PAD on failure.
729 PADOFFSET pad_findmy(const char* name)
734 =item pad_fixup_inner_anons
735 X<pad_fixup_inner_anons>
737 For any anon CVs in the pad, change CvOUTSIDE of that CV from
738 old_cv to new_cv if necessary. Needed when a newly-compiled CV has to be
739 moved to a pre-existing CV struct.
741 void pad_fixup_inner_anons(PADLIST *padlist, CV *old_cv, CV *new_cv)
749 Free the SV at offset po in the current pad.
751 void pad_free(PADOFFSET po)
759 Cleanup at end of scope during compilation: set the max seq number for
760 lexicals in this scope and warn of any lexicals that never got introduced.
770 Create a new compiling padlist, saving and updating the various global
771 vars at the same time as creating the pad itself. The following flags
772 can be OR'ed together:
774 padnew_CLONE this pad is for a cloned CV
775 padnew_SAVE save old globals
776 padnew_SAVESUB also save extra stuff for start of sub
778 PADLIST* pad_new(int flags)
786 Push a new pad frame onto the padlist, unless there's already a pad at
787 this depth, in which case don't bother creating a new one. Then give
788 the new pad an @_ in slot zero.
790 void pad_push(PADLIST *padlist, int depth)
798 Mark all the current temporaries for reuse
808 Set the entry at offset po in the current pad to sv.
809 Use the macro PAD_SETSV() rather than calling this function directly.
811 void pad_setsv(PADOFFSET po, SV* sv)
819 Abandon the tmp in the current pad at offset po and replace with a
822 void pad_swipe(PADOFFSET po, bool refadjust)
830 Tidy up a pad after we've finished compiling it:
831 * remove most stuff from the pads of anonsub prototypes;
835 void pad_tidy(padtidy_type type)
843 Free the padlist associated with a CV.
844 If parts of it happen to be current, we null the relevant
845 PL_*pad* global vars so that we don't have any dangling references left.
846 We also repoint the CvOUTSIDE of any about-to-be-orphaned
847 inner subs to the outer of this cv.
849 (This function should really be called pad_free, but the name was already
852 void pad_undef(CV* cv)
860 =head1 Per-Interpreter Variables
867 When Perl is run in debugging mode, with the B<-d> switch, this SV is a
868 boolean which indicates whether subs are being single-stepped.
869 Single-stepping is automatically turned on after every step. This is the C
870 variable which corresponds to Perl's $DB::single variable. See
876 Found in file intrpvar.h
881 When Perl is run in debugging mode, with the B<-d> switch, this GV contains
882 the SV which holds the name of the sub being debugged. This is the C
883 variable which corresponds to Perl's $DB::sub variable. See
889 Found in file intrpvar.h
894 Trace variable used when Perl is run in debugging mode, with the B<-d>
895 switch. This is the C variable which corresponds to Perl's $DB::trace
896 variable. See C<PL_DBsingle>.
901 Found in file intrpvar.h
906 The C variable which corresponds to Perl's $^W warning variable.
911 Found in file intrpvar.h
916 The GV which was last used for a filehandle input operation. (C<< <FH> >>)
921 Found in file intrpvar.h
926 The output field separator - C<$,> in Perl space.
931 Found in file intrpvar.h
936 The input record separator - C<$/> in Perl space.
941 Found in file intrpvar.h
946 =head1 Stack Manipulation Macros
953 Declare Just C<SP>. This is actually identical to C<dSP>, and declares
954 a local copy of perl's stack pointer, available via the C<SP> macro.
955 See C<SP>. (Available for backward source code compatibility with the
956 old (Perl 5.005) thread model.)
966 True if this op will be the return value of an lvalue subroutine
974 =head1 SV Manipulation Functions
981 Given a chunk of memory, link it to the head of the list of arenas,
982 and split it into a list of free SVs.
984 void sv_add_arena(char* ptr, U32 size, U32 flags)
992 Decrement the refcnt of each remaining SV, possibly triggering a
993 cleanup. This function may have to be called multiple times to free
994 SVs which are in complex self-referential hierarchies.
1004 Attempt to destroy all objects not yet freed
1006 void sv_clean_objs()
1011 =item sv_free_arenas
1014 Deallocate the memory used by all arenas. Note that all the individual SV
1015 heads and bodies within the arenas must already have been freed.
1017 void sv_free_arenas()
1025 =head1 Unicode Support
1029 =item find_uninit_var
1032 Find the name of the undefined variable (if any) that caused the operator o
1033 to issue a "Use of uninitialized value" warning.
1034 If match is true, only return a name if it's value matches uninit_sv.
1035 So roughly speaking, if a unary operator (such as OP_COS) generates a
1036 warning, then following the direct child of the op may yield an
1037 OP_PADSV or OP_GV that gives the name of the undefined variable. On the
1038 other hand, with OP_ADD there are two branches to follow, so we only print
1039 the variable name if we get an exact match.
1041 The name is returned as a mortal SV.
1043 Assumes that PL_op is the op that originally triggered the error, and that
1044 PL_comppad/PL_curpad points to the currently executing pad.
1046 SV* find_uninit_var(OP* obase, SV* uninit_sv, bool top)
1054 Print appropriate "Use of uninitialized variable" warning
1056 void report_uninit(SV* uninit_sv)
1066 The autodocumentation system was originally added to the Perl core by
1067 Benjamin Stuhl. Documentation is by whoever was kind enough to
1068 document their functions.
1072 perlguts(1), perlapi(1)
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