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)
571 =head1 Pad Data Structures
578 CV's can have CvPADLIST(cv) set to point to an AV.
580 For these purposes "forms" are a kind-of CV, eval""s are too (except they're
581 not callable at will and are always thrown away after the eval"" is done
582 executing). Require'd files are simply evals without any outer lexical
585 XSUBs don't have CvPADLIST set - dXSTARG fetches values from PL_curpad,
586 but that is really the callers pad (a slot of which is allocated by
589 The CvPADLIST AV has does not have AvREAL set, so REFCNT of component items
590 is managed "manual" (mostly in pad.c) rather than normal av.c rules.
591 The items in the AV are not SVs as for a normal AV, but other AVs:
593 0'th Entry of the CvPADLIST is an AV which represents the "names" or rather
594 the "static type information" for lexicals.
596 The CvDEPTH'th entry of CvPADLIST AV is an AV which is the stack frame at that
597 depth of recursion into the CV.
598 The 0'th slot of a frame AV is an AV which is @_.
599 other entries are storage for variables and op targets.
602 C<PL_comppad_name> is set to the names AV.
603 C<PL_comppad> is set to the frame AV for the frame CvDEPTH == 1.
604 C<PL_curpad> is set to the body of the frame AV (i.e. AvARRAY(PL_comppad)).
606 During execution, C<PL_comppad> and C<PL_curpad> refer to the live
607 frame of the currently executing sub.
609 Iterating over the names AV iterates over all possible pad
610 items. Pad slots that are SVs_PADTMP (targets/GVs/constants) end up having
611 &PL_sv_undef "names" (see pad_alloc()).
613 Only my/our variable (SVs_PADMY/SVs_PADOUR) slots get valid names.
614 The rest are op targets/GVs/constants which are statically allocated
615 or resolved at compile time. These don't have names by which they
616 can be looked up from Perl code at run time through eval"" like
617 my/our variables can be. Since they can't be looked up by "name"
618 but only by their index allocated at compile time (which is usually
619 in PL_op->op_targ), wasting a name SV for them doesn't make sense.
621 The SVs in the names AV have their PV being the name of the variable.
622 xlow+1..xhigh inclusive in the NV union is a range of cop_seq numbers for
623 which the name is valid. For typed lexicals name SV is SVt_PVMG and SvSTASH
624 points at the type. For C<our> lexicals, the type is also SVt_PVMG, with the
625 SvOURSTASH slot pointing at the stash of the associated global (so that
626 duplicate C<our> declarations in the same package can be detected). SvUVX is
627 sometimes hijacked to store the generation number during compilation.
629 If SvFAKE is set on the name SV, then that slot in the frame AV is
630 a REFCNT'ed reference to a lexical from "outside". In this case,
631 the name SV does not use xlow and xhigh to store a cop_seq range, since it is
632 in scope throughout. Instead xhigh stores some flags containing info about
633 the real lexical (is it declared in an anon, and is it capable of being
634 instantiated multiple times?), and for fake ANONs, xlow contains the index
635 within the parent's pad where the lexical's value is stored, to make
638 If the 'name' is '&' the corresponding entry in frame AV
639 is a CV representing a possible closure.
640 (SvFAKE and name of '&' is not a meaningful combination currently but could
641 become so if C<my sub foo {}> is implemented.)
643 Note that formats are treated as anon subs, and are cloned each time
644 write is called (if necessary).
646 The flag SVf_PADSTALE is cleared on lexicals each time the my() is executed,
647 and set on scope exit. This allows the 'Variable $x is not available' warning
648 to be generated in evals, such as
650 { my $x = 1; sub f { eval '$x'} } f();
652 AV * CvPADLIST(CV *cv)
660 Clone a CV: make a new CV which points to the same code etc, but which
661 has a newly-created pad built by copying the prototype pad and capturing
664 CV* cv_clone(CV* proto)
672 dump the contents of a CV
674 void cv_dump(const CV *cv, const char *title)
682 Dump the contents of a padlist
684 void do_dump_pad(I32 level, PerlIO *file, PADLIST *padlist, int full)
692 "Introduce" my variables to visible status.
702 Add an anon code entry to the current compiling pad
704 PADOFFSET pad_add_anon(SV* sv, OPCODE op_type)
712 Create a new name and associated PADMY SV in the current pad; return the
714 If C<typestash> is valid, the name is for a typed lexical; set the
715 name's stash to that value.
716 If C<ourstash> is valid, it's an our lexical, set the name's
717 SvOURSTASH to that value
719 If fake, it means we're cloning an existing entry
721 PADOFFSET pad_add_name(const char *name, HV* typestash, HV* ourstash, bool clone, bool state)
729 Allocate a new my or tmp pad entry. For a my, simply push a null SV onto
730 the end of PL_comppad, but for a tmp, scan the pad from PL_padix upwards
731 for a slot which has no name and no active value.
733 PADOFFSET pad_alloc(I32 optype, U32 tmptype)
738 =item pad_block_start
741 Update the pad compilation state variables on entry to a new block
743 void pad_block_start(int full)
751 Check for duplicate declarations: report any of:
752 * a my in the current scope with the same name;
753 * an our (anywhere in the pad) with the same name and the same stash
755 C<is_our> indicates that the name to check is an 'our' declaration
757 void pad_check_dup(const char* name, bool is_our, const HV* ourstash)
765 Find a named lexical anywhere in a chain of nested pads. Add fake entries
766 in the inner pads if it's found in an outer one.
768 Returns the offset in the bottom pad of the lex or the fake lex.
769 cv is the CV in which to start the search, and seq is the current cop_seq
770 to match against. If warn is true, print appropriate warnings. The out_*
771 vars return values, and so are pointers to where the returned values
772 should be stored. out_capture, if non-null, requests that the innermost
773 instance of the lexical is captured; out_name_sv is set to the innermost
774 matched namesv or fake namesv; out_flags returns the flags normally
775 associated with the IVX field of a fake namesv.
777 Note that pad_findlex() is recursive; it recurses up the chain of CVs,
778 then comes back down, adding fake entries as it goes. It has to be this way
779 because fake namesvs in anon protoypes have to store in xlow the index into
782 PADOFFSET pad_findlex(const char *name, const CV* cv, U32 seq, int warn, SV** out_capture, SV** out_name_sv, int *out_flags)
790 Given a lexical name, try to find its offset, first in the current pad,
791 or failing that, in the pads of any lexically enclosing subs (including
792 the complications introduced by eval). If the name is found in an outer pad,
793 then a fake entry is added to the current pad.
794 Returns the offset in the current pad, or NOT_IN_PAD on failure.
796 PADOFFSET pad_findmy(const char* name)
801 =item pad_fixup_inner_anons
802 X<pad_fixup_inner_anons>
804 For any anon CVs in the pad, change CvOUTSIDE of that CV from
805 old_cv to new_cv if necessary. Needed when a newly-compiled CV has to be
806 moved to a pre-existing CV struct.
808 void pad_fixup_inner_anons(PADLIST *padlist, CV *old_cv, CV *new_cv)
816 Free the SV at offset po in the current pad.
818 void pad_free(PADOFFSET po)
826 Cleanup at end of scope during compilation: set the max seq number for
827 lexicals in this scope and warn of any lexicals that never got introduced.
837 Create a new compiling padlist, saving and updating the various global
838 vars at the same time as creating the pad itself. The following flags
839 can be OR'ed together:
841 padnew_CLONE this pad is for a cloned CV
842 padnew_SAVE save old globals
843 padnew_SAVESUB also save extra stuff for start of sub
845 PADLIST* pad_new(int flags)
853 Push a new pad frame onto the padlist, unless there's already a pad at
854 this depth, in which case don't bother creating a new one. Then give
855 the new pad an @_ in slot zero.
857 void pad_push(PADLIST *padlist, int depth)
865 Mark all the current temporaries for reuse
875 Set the entry at offset po in the current pad to sv.
876 Use the macro PAD_SETSV() rather than calling this function directly.
878 void pad_setsv(PADOFFSET po, SV* sv)
886 Abandon the tmp in the current pad at offset po and replace with a
889 void pad_swipe(PADOFFSET po, bool refadjust)
897 Tidy up a pad after we've finished compiling it:
898 * remove most stuff from the pads of anonsub prototypes;
902 void pad_tidy(padtidy_type type)
910 Free the padlist associated with a CV.
911 If parts of it happen to be current, we null the relevant
912 PL_*pad* global vars so that we don't have any dangling references left.
913 We also repoint the CvOUTSIDE of any about-to-be-orphaned
914 inner subs to the outer of this cv.
916 (This function should really be called pad_free, but the name was already
919 void pad_undef(CV* cv)
927 =head1 Stack Manipulation Macros
934 Declare Just C<SP>. This is actually identical to C<dSP>, and declares
935 a local copy of perl's stack pointer, available via the C<SP> macro.
936 See C<SP>. (Available for backward source code compatibility with the
937 old (Perl 5.005) thread model.)
947 True if this op will be the return value of an lvalue subroutine
955 =head1 SV Manipulation Functions
962 Given a chunk of memory, link it to the head of the list of arenas,
963 and split it into a list of free SVs.
965 void sv_add_arena(char* ptr, U32 size, U32 flags)
973 Decrement the refcnt of each remaining SV, possibly triggering a
974 cleanup. This function may have to be called multiple times to free
975 SVs which are in complex self-referential hierarchies.
985 Attempt to destroy all objects not yet freed
995 Deallocate the memory used by all arenas. Note that all the individual SV
996 heads and bodies within the arenas must already have been freed.
998 void sv_free_arenas()
1006 =head1 Unicode Support
1010 =item find_uninit_var
1013 Find the name of the undefined variable (if any) that caused the operator o
1014 to issue a "Use of uninitialized value" warning.
1015 If match is true, only return a name if it's value matches uninit_sv.
1016 So roughly speaking, if a unary operator (such as OP_COS) generates a
1017 warning, then following the direct child of the op may yield an
1018 OP_PADSV or OP_GV that gives the name of the undefined variable. On the
1019 other hand, with OP_ADD there are two branches to follow, so we only print
1020 the variable name if we get an exact match.
1022 The name is returned as a mortal SV.
1024 Assumes that PL_op is the op that originally triggered the error, and that
1025 PL_comppad/PL_curpad points to the currently executing pad.
1027 SV* find_uninit_var(OP* obase, SV* uninit_sv, bool top)
1035 Print appropriate "Use of uninitialized variable" warning
1037 void report_uninit(SV* uninit_sv)
1047 The autodocumentation system was originally added to the Perl core by
1048 Benjamin Stuhl. Documentation is by whoever was kind enough to
1049 document their functions.
1053 perlguts(1), perlapi(1)
https://perl5.git.perl.org / perl5.git / blob