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
356 =head1 Global Variables
363 When Perl is run in debugging mode, with the B<-d> switch, this SV is a
364 boolean which indicates whether subs are being single-stepped.
365 Single-stepping is automatically turned on after every step. This is the C
366 variable which corresponds to Perl's $DB::single variable. See
372 Found in file intrpvar.h
377 When Perl is run in debugging mode, with the B<-d> switch, this GV contains
378 the SV which holds the name of the sub being debugged. This is the C
379 variable which corresponds to Perl's $DB::sub variable. See
385 Found in file intrpvar.h
390 Trace variable used when Perl is run in debugging mode, with the B<-d>
391 switch. This is the C variable which corresponds to Perl's $DB::trace
392 variable. See C<PL_DBsingle>.
397 Found in file intrpvar.h
402 The C variable which corresponds to Perl's $^W warning variable.
407 Found in file intrpvar.h
412 The GV which was last used for a filehandle input operation. (C<< <FH> >>)
417 Found in file thrdvar.h
422 The output field separator - C<$,> in Perl space.
427 Found in file thrdvar.h
432 The input record separator - C<$/> in Perl space.
437 Found in file thrdvar.h
449 Returns C<TRUE> if given the name of a magical GV.
451 Currently only useful internally when determining if a GV should be
452 created even in rvalue contexts.
454 C<flags> is not used at present but available for future extension to
455 allow selecting particular classes of magical variable.
457 Currently assumes that C<name> is NUL terminated (as well as len being valid).
458 This assumption is met by all callers within the perl core, which all pass
459 pointers returned by SvPV.
461 bool is_gv_magical(const char *name, STRLEN len, U32 flags)
466 =item is_gv_magical_sv
469 Returns C<TRUE> if given the name of a magical GV. Calls is_gv_magical.
471 bool is_gv_magical_sv(SV *name, U32 flags)
479 =head1 Hash Manipulation Functions
483 =item refcounted_he_chain_2hv
484 X<refcounted_he_chain_2hv>
486 Generates and returns a C<HV *> by walking up the tree starting at the passed
487 in C<struct refcounted_he *>.
489 HV * refcounted_he_chain_2hv(const struct refcounted_he *c)
494 =item refcounted_he_free
495 X<refcounted_he_free>
497 Decrements the reference count of the passed in C<struct refcounted_he *>
498 by one. If the reference count reaches zero the structure's memory is freed,
499 and C<refcounted_he_free> iterates onto the parent node.
501 void refcounted_he_free(struct refcounted_he *he)
506 =item refcounted_he_new
509 Creates a new C<struct refcounted_he>. As S<key> is copied, and value is
510 stored in a compact form, all references remain the property of the caller.
511 The C<struct refcounted_he> is returned with a reference count of 1.
513 struct refcounted_he * refcounted_he_new(struct refcounted_he *const parent, SV *const key, SV *const value)
528 Function called by C<do_readline> to spawn a glob (or do the glob inside
529 perl on VMS). This code used to be inline, but now perl uses C<File::Glob>
530 this glob starter is only used by miniperl during the build process.
531 Moving it away shrinks pp_hot.c; shrinking pp_hot.c helps speed perl up.
533 PerlIO* start_glob(SV* pattern, IO *io)
541 =head1 Magical Functions
548 Triggered by a delete from %^H, records the key to
549 C<PL_compiling.cop_hints_hash>.
551 int magic_sethint(SV* sv, MAGIC* mg)
559 Copy some of the magic from an existing SV to new localized version of
560 that SV. Container magic (eg %ENV, $1, tie) gets copied, value magic
561 doesn't (eg taint, pos).
563 void mg_localize(SV* sv, SV* nsv)
575 =item mro_isa_changed_in
576 X<mro_isa_changed_in>
578 Takes the necessary steps (cache invalidations, mostly)
579 when the @ISA of the given package has changed. Invoked
580 by the C<setisa> magic, should not need to invoke directly.
582 void mro_isa_changed_in(HV* stash)
590 =head1 Pad Data Structures
597 CV's can have CvPADLIST(cv) set to point to an AV.
599 For these purposes "forms" are a kind-of CV, eval""s are too (except they're
600 not callable at will and are always thrown away after the eval"" is done
601 executing). Require'd files are simply evals without any outer lexical
604 XSUBs don't have CvPADLIST set - dXSTARG fetches values from PL_curpad,
605 but that is really the callers pad (a slot of which is allocated by
608 The CvPADLIST AV has does not have AvREAL set, so REFCNT of component items
609 is managed "manual" (mostly in pad.c) rather than normal av.c rules.
610 The items in the AV are not SVs as for a normal AV, but other AVs:
612 0'th Entry of the CvPADLIST is an AV which represents the "names" or rather
613 the "static type information" for lexicals.
615 The CvDEPTH'th entry of CvPADLIST AV is an AV which is the stack frame at that
616 depth of recursion into the CV.
617 The 0'th slot of a frame AV is an AV which is @_.
618 other entries are storage for variables and op targets.
621 C<PL_comppad_name> is set to the names AV.
622 C<PL_comppad> is set to the frame AV for the frame CvDEPTH == 1.
623 C<PL_curpad> is set to the body of the frame AV (i.e. AvARRAY(PL_comppad)).
625 During execution, C<PL_comppad> and C<PL_curpad> refer to the live
626 frame of the currently executing sub.
628 Iterating over the names AV iterates over all possible pad
629 items. Pad slots that are SVs_PADTMP (targets/GVs/constants) end up having
630 &PL_sv_undef "names" (see pad_alloc()).
632 Only my/our variable (SVs_PADMY/SVs_PADOUR) slots get valid names.
633 The rest are op targets/GVs/constants which are statically allocated
634 or resolved at compile time. These don't have names by which they
635 can be looked up from Perl code at run time through eval"" like
636 my/our variables can be. Since they can't be looked up by "name"
637 but only by their index allocated at compile time (which is usually
638 in PL_op->op_targ), wasting a name SV for them doesn't make sense.
640 The SVs in the names AV have their PV being the name of the variable.
641 xlow+1..xhigh inclusive in the NV union is a range of cop_seq numbers for
642 which the name is valid. For typed lexicals name SV is SVt_PVMG and SvSTASH
643 points at the type. For C<our> lexicals, the type is also SVt_PVMG, with the
644 SvOURSTASH slot pointing at the stash of the associated global (so that
645 duplicate C<our> declarations in the same package can be detected). SvUVX is
646 sometimes hijacked to store the generation number during compilation.
648 If SvFAKE is set on the name SV, then that slot in the frame AV is
649 a REFCNT'ed reference to a lexical from "outside". In this case,
650 the name SV does not use xlow and xhigh to store a cop_seq range, since it is
651 in scope throughout. Instead xhigh stores some flags containing info about
652 the real lexical (is it declared in an anon, and is it capable of being
653 instantiated multiple times?), and for fake ANONs, xlow contains the index
654 within the parent's pad where the lexical's value is stored, to make
657 If the 'name' is '&' the corresponding entry in frame AV
658 is a CV representing a possible closure.
659 (SvFAKE and name of '&' is not a meaningful combination currently but could
660 become so if C<my sub foo {}> is implemented.)
662 Note that formats are treated as anon subs, and are cloned each time
663 write is called (if necessary).
665 The flag SVf_PADSTALE is cleared on lexicals each time the my() is executed,
666 and set on scope exit. This allows the 'Variable $x is not available' warning
667 to be generated in evals, such as
669 { my $x = 1; sub f { eval '$x'} } f();
671 AV * CvPADLIST(CV *cv)
679 Clone a CV: make a new CV which points to the same code etc, but which
680 has a newly-created pad built by copying the prototype pad and capturing
683 CV* cv_clone(CV* proto)
691 dump the contents of a CV
693 void cv_dump(const CV *cv, const char *title)
701 Dump the contents of a padlist
703 void do_dump_pad(I32 level, PerlIO *file, PADLIST *padlist, int full)
711 "Introduce" my variables to visible status.
721 Add an anon code entry to the current compiling pad
723 PADOFFSET pad_add_anon(SV* sv, OPCODE op_type)
731 Create a new name and associated PADMY SV in the current pad; return the
733 If C<typestash> is valid, the name is for a typed lexical; set the
734 name's stash to that value.
735 If C<ourstash> is valid, it's an our lexical, set the name's
736 SvOURSTASH to that value
738 If fake, it means we're cloning an existing entry
740 PADOFFSET pad_add_name(const char *name, HV* typestash, HV* ourstash, bool clone, bool state)
748 Allocate a new my or tmp pad entry. For a my, simply push a null SV onto
749 the end of PL_comppad, but for a tmp, scan the pad from PL_padix upwards
750 for a slot which has no name and no active value.
752 PADOFFSET pad_alloc(I32 optype, U32 tmptype)
757 =item pad_block_start
760 Update the pad compilation state variables on entry to a new block
762 void pad_block_start(int full)
770 Check for duplicate declarations: report any of:
771 * a my in the current scope with the same name;
772 * an our (anywhere in the pad) with the same name and the same stash
774 C<is_our> indicates that the name to check is an 'our' declaration
776 void pad_check_dup(const char* name, bool is_our, const HV* ourstash)
784 Find a named lexical anywhere in a chain of nested pads. Add fake entries
785 in the inner pads if it's found in an outer one.
787 Returns the offset in the bottom pad of the lex or the fake lex.
788 cv is the CV in which to start the search, and seq is the current cop_seq
789 to match against. If warn is true, print appropriate warnings. The out_*
790 vars return values, and so are pointers to where the returned values
791 should be stored. out_capture, if non-null, requests that the innermost
792 instance of the lexical is captured; out_name_sv is set to the innermost
793 matched namesv or fake namesv; out_flags returns the flags normally
794 associated with the IVX field of a fake namesv.
796 Note that pad_findlex() is recursive; it recurses up the chain of CVs,
797 then comes back down, adding fake entries as it goes. It has to be this way
798 because fake namesvs in anon protoypes have to store in xlow the index into
801 PADOFFSET pad_findlex(const char *name, const CV* cv, U32 seq, int warn, SV** out_capture, SV** out_name_sv, int *out_flags)
809 Given a lexical name, try to find its offset, first in the current pad,
810 or failing that, in the pads of any lexically enclosing subs (including
811 the complications introduced by eval). If the name is found in an outer pad,
812 then a fake entry is added to the current pad.
813 Returns the offset in the current pad, or NOT_IN_PAD on failure.
815 PADOFFSET pad_findmy(const char* name)
820 =item pad_fixup_inner_anons
821 X<pad_fixup_inner_anons>
823 For any anon CVs in the pad, change CvOUTSIDE of that CV from
824 old_cv to new_cv if necessary. Needed when a newly-compiled CV has to be
825 moved to a pre-existing CV struct.
827 void pad_fixup_inner_anons(PADLIST *padlist, CV *old_cv, CV *new_cv)
835 Free the SV at offset po in the current pad.
837 void pad_free(PADOFFSET po)
845 Cleanup at end of scope during compilation: set the max seq number for
846 lexicals in this scope and warn of any lexicals that never got introduced.
856 Create a new compiling padlist, saving and updating the various global
857 vars at the same time as creating the pad itself. The following flags
858 can be OR'ed together:
860 padnew_CLONE this pad is for a cloned CV
861 padnew_SAVE save old globals
862 padnew_SAVESUB also save extra stuff for start of sub
864 PADLIST* pad_new(int flags)
872 Push a new pad frame onto the padlist, unless there's already a pad at
873 this depth, in which case don't bother creating a new one. Then give
874 the new pad an @_ in slot zero.
876 void pad_push(PADLIST *padlist, int depth)
884 Mark all the current temporaries for reuse
894 Set the entry at offset po in the current pad to sv.
895 Use the macro PAD_SETSV() rather than calling this function directly.
897 void pad_setsv(PADOFFSET po, SV* sv)
905 Abandon the tmp in the current pad at offset po and replace with a
908 void pad_swipe(PADOFFSET po, bool refadjust)
916 Tidy up a pad after we've finished compiling it:
917 * remove most stuff from the pads of anonsub prototypes;
921 void pad_tidy(padtidy_type type)
929 Free the padlist associated with a CV.
930 If parts of it happen to be current, we null the relevant
931 PL_*pad* global vars so that we don't have any dangling references left.
932 We also repoint the CvOUTSIDE of any about-to-be-orphaned
933 inner subs to the outer of this cv.
935 (This function should really be called pad_free, but the name was already
938 void pad_undef(CV* cv)
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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