X-Git-Url: https://perl5.git.perl.org/perl5.git/blobdiff_plain/a4f1a0295dfc0733a51ca0623d486d082d04773a..d491518e36bdf6ee0e29d7043e72b5f41100ece6:/cv.h diff --git a/cv.h b/cv.h index 824517c..ada2e4d 100644 --- a/cv.h +++ b/cv.h @@ -1,21 +1,25 @@ /* cv.h * - * Copyright (c) 1991-2002, Larry Wall + * Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1999, + * 2000, 2001, 2002, 2003, 2004, 2005, by Larry Wall and others * * You may distribute under the terms of either the GNU General Public * License or the Artistic License, as specified in the README file. * */ -/* This structure much match XPVCV in B/C.pm and the beginning of XPVFM +/* This structure must match XPVCV in B/C.pm and the beginning of XPVFM * in sv.h */ struct xpvcv { - char * xpv_pv; /* pointer to malloced string */ + NV xnv_nv; /* numeric value, if any */ STRLEN xpv_cur; /* length of xp_pv as a C string */ STRLEN xpv_len; /* allocated size */ - IV xof_off; /* integer value */ - NV xnv_nv; /* numeric value, if any */ + union { + IV xivu_iv; /* integer value or pv offset */ + UV xivu_uv; + void * xivu_p1; + } xiv_u; MAGIC* xmg_magic; /* magic for scalar array */ HV* xmg_stash; /* class package */ @@ -27,13 +31,12 @@ struct xpvcv { GV * xcv_gv; char * xcv_file; long xcv_depth; /* >= 2 indicates recursive call */ - AV * xcv_padlist; + PADLIST * xcv_padlist; CV * xcv_outside; -#ifdef USE_5005THREADS - perl_mutex *xcv_mutexp; - struct perl_thread *xcv_owner; /* current owner thread */ -#endif /* USE_5005THREADS */ cv_flags_t xcv_flags; + U32 xcv_outside_seq; /* the COP sequence (at the point of our + * compilation) in the lexically enclosing + * sub */ }; /* @@ -68,23 +71,28 @@ Returns the stash of the CV. #define CvDEPTH(sv) ((XPVCV*)SvANY(sv))->xcv_depth #define CvPADLIST(sv) ((XPVCV*)SvANY(sv))->xcv_padlist #define CvOUTSIDE(sv) ((XPVCV*)SvANY(sv))->xcv_outside -#ifdef USE_5005THREADS -#define CvMUTEXP(sv) ((XPVCV*)SvANY(sv))->xcv_mutexp -#define CvOWNER(sv) ((XPVCV*)SvANY(sv))->xcv_owner -#endif /* USE_5005THREADS */ #define CvFLAGS(sv) ((XPVCV*)SvANY(sv))->xcv_flags +#define CvOUTSIDE_SEQ(sv) ((XPVCV*)SvANY(sv))->xcv_outside_seq #define CVf_CLONE 0x0001 /* anon CV uses external lexicals */ #define CVf_CLONED 0x0002 /* a clone of one of those */ #define CVf_ANON 0x0004 /* CvGV() can't be trusted */ #define CVf_OLDSTYLE 0x0008 -#define CVf_UNIQUE 0x0010 /* can't be cloned */ +#define CVf_UNIQUE 0x0010 /* sub is only called once (eg PL_main_cv, + * require, eval). Not to be confused + * with the GVf_UNIQUE flag associated + * with the :unique attribute */ #define CVf_NODEBUG 0x0020 /* no DB::sub indirection for this CV (esp. useful for special XSUBs) */ #define CVf_METHOD 0x0040 /* CV is explicitly marked as a method */ #define CVf_LOCKED 0x0080 /* CV locks itself or first arg on entry */ #define CVf_LVALUE 0x0100 /* CV return value can be used as lvalue */ #define CVf_CONST 0x0200 /* inlinable sub */ +#define CVf_WEAKOUTSIDE 0x0400 /* CvOUTSIDE isn't ref counted */ +#define CVf_ASSERTION 0x0800 /* CV called only when asserting */ + +/* This symbol for optimised communication between toke.c and op.c: */ +#define CVf_BUILTIN_ATTRS (CVf_METHOD|CVf_LOCKED|CVf_LVALUE|CVf_ASSERTION) #define CvCLONE(cv) (CvFLAGS(cv) & CVf_CLONE) #define CvCLONE_on(cv) (CvFLAGS(cv) |= CVf_CLONE) @@ -124,11 +132,15 @@ Returns the stash of the CV. #define CvLVALUE_on(cv) (CvFLAGS(cv) |= CVf_LVALUE) #define CvLVALUE_off(cv) (CvFLAGS(cv) &= ~CVf_LVALUE) +#define CvASSERTION(cv) (CvFLAGS(cv) & CVf_ASSERTION) +#define CvASSERTION_on(cv) (CvFLAGS(cv) |= CVf_ASSERTION) +#define CvASSERTION_off(cv) (CvFLAGS(cv) &= ~CVf_ASSERTION) + #define CvEVAL(cv) (CvUNIQUE(cv) && !SvFAKE(cv)) #define CvEVAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_off(cv)) #define CvEVAL_off(cv) CvUNIQUE_off(cv) -/* BEGIN|INIT|END */ +/* BEGIN|CHECK|INIT|END */ #define CvSPECIAL(cv) (CvUNIQUE(cv) && SvFAKE(cv)) #define CvSPECIAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_on(cv)) #define CvSPECIAL_off(cv) (CvUNIQUE_off(cv),SvFAKE_off(cv)) @@ -137,61 +149,72 @@ Returns the stash of the CV. #define CvCONST_on(cv) (CvFLAGS(cv) |= CVf_CONST) #define CvCONST_off(cv) (CvFLAGS(cv) &= ~CVf_CONST) -/* -=head1 Pad Data Structures - -=for apidoc m|AV *|CvPADLIST|CV *cv -CV's can have CvPADLIST(cv) set to point to an AV. - -For these purposes "forms" are a kind-of CV, eval""s are too (except they're -not callable at will and are always thrown away after the eval"" is done -executing). - -XSUBs don't have CvPADLIST set - dXSTARG fetches values from PL_curpad, -but that is really the callers pad (a slot of which is allocated by -every entersub). - -The CvPADLIST AV has does not have AvREAL set, so REFCNT of component items -is managed "manual" (mostly in op.c) rather than normal av.c rules. -The items in the AV are not SVs as for a normal AV, but other AVs: - -0'th Entry of the CvPADLIST is an AV which represents the "names" or rather -the "static type information" for lexicals. +#define CvWEAKOUTSIDE(cv) (CvFLAGS(cv) & CVf_WEAKOUTSIDE) +#define CvWEAKOUTSIDE_on(cv) (CvFLAGS(cv) |= CVf_WEAKOUTSIDE) +#define CvWEAKOUTSIDE_off(cv) (CvFLAGS(cv) &= ~CVf_WEAKOUTSIDE) -The CvDEPTH'th entry of CvPADLIST AV is an AV which is the stack frame at that -depth of recursion into the CV. -The 0'th slot of a frame AV is an AV which is @_. -other entries are storage for variables and op targets. -During compilation: -C is set the the the names AV. -C is set the the frame AV for the frame CvDEPTH == 1. -C is set the body of the frame AV (i.e. AvARRAY(PL_comppad)). - -Itterating over the names AV itterates over all possible pad -items. Pad slots that are SVs_PADTMP (targets/GVs/constants) end up having -&PL_sv_undef "names" (see pad_alloc()). - -Only my/our variable (SVs_PADMY/SVs_PADOUR) slots get valid names. -The rest are op targets/GVs/constants which are statically allocated -or resolved at compile time. These don't have names by which they -can be looked up from Perl code at run time through eval"" like -my/our variables can be. Since they can't be looked up by "name" -but only by their index allocated at compile time (which is usually -in PL_op->op_targ), wasting a name SV for them doesn't make sense. - -The SVs in the names AV have their PV being the name of the variable. -NV+1..IV inclusive is a range of cop_seq numbers for which the name is valid. -For typed lexicals name SV is SVt_PVMG and SvSTASH points at the type. - -If SvFAKE is set on the name SV then slot in the frame AVs are -a REFCNT'ed references to a lexical from "outside". - -If the 'name' is '&' the the corresponding entry in frame AV -is a CV representing a possible closure. -(SvFAKE and name of '&' is not a meaningful combination currently but could -become so if C is implemented.) +/* +=head1 CV reference counts and CvOUTSIDE + +=for apidoc m|bool|CvWEAKOUTSIDE|CV *cv + +Each CV has a pointer, C, to its lexically enclosing +CV (if any). Because pointers to anonymous sub prototypes are +stored in C<&> pad slots, it is a possible to get a circular reference, +with the parent pointing to the child and vice-versa. To avoid the +ensuing memory leak, we do not increment the reference count of the CV +pointed to by C in the I that the parent +has a C<&> pad slot pointing back to us. In this case, we set the +C flag in the child. This allows us to determine under what +circumstances we should decrement the refcount of the parent when freeing +the child. + +There is a further complication with non-closure anonymous subs (i.e. those +that do not refer to any lexicals outside that sub). In this case, the +anonymous prototype is shared rather than being cloned. This has the +consequence that the parent may be freed while there are still active +children, eg + + BEGIN { $a = sub { eval '$x' } } + +In this case, the BEGIN is freed immediately after execution since there +are no active references to it: the anon sub prototype has +C set since it's not a closure, and $a points to the same +CV, so it doesn't contribute to BEGIN's refcount either. When $a is +executed, the C causes the chain of Cs to be followed, +and the freed BEGIN is accessed. + +To avoid this, whenever a CV and its associated pad is freed, any +C<&> entries in the pad are explicitly removed from the pad, and if the +refcount of the pointed-to anon sub is still positive, then that +child's C is set to point to its grandparent. This will only +occur in the single specific case of a non-closure anon prototype +having one or more active references (such as C<$a> above). + +One other thing to consider is that a CV may be merely undefined +rather than freed, eg C. In this case, its refcount may +not have reached zero, but we still delete its pad and its C etc. +Since various children may still have their C pointing at this +undefined CV, we keep its own C for the time being, so that +the chain of lexical scopes is unbroken. For example, the following +should print 123: + + my $x = 123; + sub tmp { sub { eval '$x' } } + my $a = tmp(); + undef &tmp; + print $a->(); =cut */ +/* + * Local variables: + * c-indentation-style: bsd + * c-basic-offset: 4 + * indent-tabs-mode: t + * End: + * + * ex: set ts=8 sts=4 sw=4 noet: + */