/* 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 */
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 */
};
/*
#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)
#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))
#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<PL_comppad_name> is set the the the names AV.
-C<PL_comppad> is set the the frame AV for the frame CvDEPTH == 1.
-C<PL_curpad> 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<my sub foo {}> is implemented.)
+/*
+=head1 CV reference counts and CvOUTSIDE
+
+=for apidoc m|bool|CvWEAKOUTSIDE|CV *cv
+
+Each CV has a pointer, C<CvOUTSIDE()>, 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<CvOUTSIDE> in the I<one specific instance> that the parent
+has a C<&> pad slot pointing back to us. In this case, we set the
+C<CvWEAKOUTSIDE> 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<CvWEAKOUTSIDE> 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 $a is
+executed, the C<eval '$x'> causes the chain of C<CvOUTSIDE>s 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<CvOUTSIDE> 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<undef &foo>. In this case, its refcount may
+not have reached zero, but we still delete its pad and its C<CvROOT> etc.
+Since various children may still have their C<CvOUTSIDE> pointing at this
+undefined CV, we keep its own C<CvOUTSIDE> 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:
+ */
https://perl5.git.perl.org / perl5.git / blobdiff