/* cv.h
*
- * Copyright (c) 1991-2001, Larry Wall
+ * Copyright (c) 1991-2003, Larry Wall
*
* 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 */
+ char * xpv_pv; /* pointer to malloced string (for prototype) */
STRLEN xpv_cur; /* length of xp_pv as a C string */
STRLEN xpv_len; /* allocated size */
IV xof_off; /* integer value */
HV * xcv_stash;
OP * xcv_start;
OP * xcv_root;
- void (*xcv_xsub) (pTHXo_ CV*);
+ void (*xcv_xsub) (pTHX_ CV*);
ANY xcv_xsubany;
GV * xcv_gv;
char * xcv_file;
long xcv_depth; /* >= 2 indicates recursive call */
- AV * xcv_padlist;
+ PADLIST * xcv_padlist;
CV * xcv_outside;
-#ifdef USE_THREADS
- perl_mutex *xcv_mutexp;
- struct perl_thread *xcv_owner; /* current owner thread */
-#endif /* USE_THREADS */
cv_flags_t xcv_flags;
+ U32 xcv_outside_seq; /* the COP sequence (at the point of our
+ * compilation) in the lexically enclosing
+ * sub */
};
/*
+=head1 Handy Values
+
=for apidoc AmU||Nullcv
Null CV pointer.
+=head1 CV Manipulation Functions
+
=for apidoc Am|HV*|CvSTASH|CV* cv
Returns the stash of the CV.
#else
# define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = CopFILE(cop))
#endif
-#define CvFILEGV(sv) (gv_fetchfile(CvFILE(sv))
+#define CvFILEGV(sv) (gv_fetchfile(CvFILE(sv)))
#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_THREADS
-#define CvMUTEXP(sv) ((XPVCV*)SvANY(sv))->xcv_mutexp
-#define CvOWNER(sv) ((XPVCV*)SvANY(sv))->xcv_owner
-#endif /* USE_THREADS */
#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_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(cv) (CvFLAGS(cv) & CVf_CONST)
#define CvCONST_on(cv) (CvFLAGS(cv) |= CVf_CONST)
#define CvCONST_off(cv) (CvFLAGS(cv) &= ~CVf_CONST)
+
+#define CvWEAKOUTSIDE(cv) (CvFLAGS(cv) & CVf_WEAKOUTSIDE)
+#define CvWEAKOUTSIDE_on(cv) (CvFLAGS(cv) |= CVf_WEAKOUTSIDE)
+#define CvWEAKOUTSIDE_off(cv) (CvFLAGS(cv) &= ~CVf_WEAKOUTSIDE)
+
+
+/*
+=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 (ie 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
+*/
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