3 * Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1999, 2000, 2001,
4 * 2002, 2003, 2004, 2005, 2006, 2007, 2008 by Larry Wall and others
6 * You may distribute under the terms of either the GNU General Public
7 * License or the Artistic License, as specified in the README file.
11 /* This structure must the beginning of XPVFM in sv.h */
16 I32 xcv_depth; /* >= 2 indicates recursive call */
22 =for apidoc AmU||Nullcv
25 (deprecated - use C<(CV *)NULL> instead)
27 =head1 CV Manipulation Functions
29 =for apidoc Am|HV*|CvSTASH|CV* cv
30 Returns the stash of the CV.
36 # define Nullcv Null(CV*)
39 #define CvSTASH(sv) (0+((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_stash)
40 #define CvSTASH_set(cv,st) Perl_cvstash_set(aTHX_ cv, st)
41 #define CvSTART(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_start_u.xcv_start
42 #define CvROOT(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_root_u.xcv_root
43 #define CvXSUB(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_root_u.xcv_xsub
44 #define CvXSUBANY(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_start_u.xcv_xsubany
45 #define CvGV(sv) (0+((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_gv)
46 #define CvGV_set(cv,gv) Perl_cvgv_set(aTHX_ cv, gv)
47 #define CvFILE(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_file
49 # define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = savepv(CopFILE(cop)))
51 # define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = CopFILE(cop))
53 #define CvFILEGV(sv) (gv_fetchfile(CvFILE(sv)))
54 #if defined(__GNUC__) && !defined(PERL_GCC_BRACE_GROUPS_FORBIDDEN)
55 # define CvDEPTH(sv) (*({const CV *const _cvdepth = (const CV *)sv; \
56 assert(SvTYPE(_cvdepth) == SVt_PVCV); \
57 &((XPVCV*)SvANY(_cvdepth))->xcv_depth; \
60 # define CvDEPTH(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_depth
62 #define CvPADLIST(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_padlist
63 #define CvOUTSIDE(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_outside
64 #define CvFLAGS(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_flags
65 #define CvOUTSIDE_SEQ(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_outside_seq
67 #define CVf_METHOD 0x0001 /* CV is explicitly marked as a method */
68 #define CVf_LVALUE 0x0002 /* CV return value can be used as lvalue */
69 #define CVf_CONST 0x0004 /* inlinable sub */
70 #define CVf_ISXSUB 0x0008 /* CV is an XSUB, not pure perl. */
72 #define CVf_WEAKOUTSIDE 0x0010 /* CvOUTSIDE isn't ref counted */
73 #define CVf_CLONE 0x0020 /* anon CV uses external lexicals */
74 #define CVf_CLONED 0x0040 /* a clone of one of those */
75 #define CVf_ANON 0x0080 /* CV is not pointed to by a GV */
76 #define CVf_UNIQUE 0x0100 /* sub is only called once (eg PL_main_cv,
78 #define CVf_NODEBUG 0x0200 /* no DB::sub indirection for this CV
79 (esp. useful for special XSUBs) */
80 #define CVf_CVGV_RC 0x0400 /* CvGV is reference counted */
82 /* This symbol for optimised communication between toke.c and op.c: */
83 #define CVf_BUILTIN_ATTRS (CVf_METHOD|CVf_LVALUE)
85 #define CvCLONE(cv) (CvFLAGS(cv) & CVf_CLONE)
86 #define CvCLONE_on(cv) (CvFLAGS(cv) |= CVf_CLONE)
87 #define CvCLONE_off(cv) (CvFLAGS(cv) &= ~CVf_CLONE)
89 #define CvCLONED(cv) (CvFLAGS(cv) & CVf_CLONED)
90 #define CvCLONED_on(cv) (CvFLAGS(cv) |= CVf_CLONED)
91 #define CvCLONED_off(cv) (CvFLAGS(cv) &= ~CVf_CLONED)
93 #define CvANON(cv) (CvFLAGS(cv) & CVf_ANON)
94 #define CvANON_on(cv) (CvFLAGS(cv) |= CVf_ANON)
95 #define CvANON_off(cv) (CvFLAGS(cv) &= ~CVf_ANON)
97 #define CvUNIQUE(cv) (CvFLAGS(cv) & CVf_UNIQUE)
98 #define CvUNIQUE_on(cv) (CvFLAGS(cv) |= CVf_UNIQUE)
99 #define CvUNIQUE_off(cv) (CvFLAGS(cv) &= ~CVf_UNIQUE)
101 #define CvNODEBUG(cv) (CvFLAGS(cv) & CVf_NODEBUG)
102 #define CvNODEBUG_on(cv) (CvFLAGS(cv) |= CVf_NODEBUG)
103 #define CvNODEBUG_off(cv) (CvFLAGS(cv) &= ~CVf_NODEBUG)
105 #define CvMETHOD(cv) (CvFLAGS(cv) & CVf_METHOD)
106 #define CvMETHOD_on(cv) (CvFLAGS(cv) |= CVf_METHOD)
107 #define CvMETHOD_off(cv) (CvFLAGS(cv) &= ~CVf_METHOD)
109 #define CvLVALUE(cv) (CvFLAGS(cv) & CVf_LVALUE)
110 #define CvLVALUE_on(cv) (CvFLAGS(cv) |= CVf_LVALUE)
111 #define CvLVALUE_off(cv) (CvFLAGS(cv) &= ~CVf_LVALUE)
113 #define CvEVAL(cv) (CvUNIQUE(cv) && !SvFAKE(cv))
114 #define CvEVAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_off(cv))
115 #define CvEVAL_off(cv) CvUNIQUE_off(cv)
117 /* BEGIN|CHECK|INIT|UNITCHECK|END */
118 #define CvSPECIAL(cv) (CvUNIQUE(cv) && SvFAKE(cv))
119 #define CvSPECIAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_on(cv))
120 #define CvSPECIAL_off(cv) (CvUNIQUE_off(cv),SvFAKE_off(cv))
122 #define CvCONST(cv) (CvFLAGS(cv) & CVf_CONST)
123 #define CvCONST_on(cv) (CvFLAGS(cv) |= CVf_CONST)
124 #define CvCONST_off(cv) (CvFLAGS(cv) &= ~CVf_CONST)
126 #define CvWEAKOUTSIDE(cv) (CvFLAGS(cv) & CVf_WEAKOUTSIDE)
127 #define CvWEAKOUTSIDE_on(cv) (CvFLAGS(cv) |= CVf_WEAKOUTSIDE)
128 #define CvWEAKOUTSIDE_off(cv) (CvFLAGS(cv) &= ~CVf_WEAKOUTSIDE)
130 #define CvISXSUB(cv) (CvFLAGS(cv) & CVf_ISXSUB)
131 #define CvISXSUB_on(cv) (CvFLAGS(cv) |= CVf_ISXSUB)
132 #define CvISXSUB_off(cv) (CvFLAGS(cv) &= ~CVf_ISXSUB)
134 #define CvCVGV_RC(cv) (CvFLAGS(cv) & CVf_CVGV_RC)
135 #define CvCVGV_RC_on(cv) (CvFLAGS(cv) |= CVf_CVGV_RC)
136 #define CvCVGV_RC_off(cv) (CvFLAGS(cv) &= ~CVf_CVGV_RC)
138 /* Flags for newXS_flags */
139 #define XS_DYNAMIC_FILENAME 0x01 /* The filename isn't static */
142 =head1 CV reference counts and CvOUTSIDE
144 =for apidoc m|bool|CvWEAKOUTSIDE|CV *cv
146 Each CV has a pointer, C<CvOUTSIDE()>, to its lexically enclosing
147 CV (if any). Because pointers to anonymous sub prototypes are
148 stored in C<&> pad slots, it is a possible to get a circular reference,
149 with the parent pointing to the child and vice-versa. To avoid the
150 ensuing memory leak, we do not increment the reference count of the CV
151 pointed to by C<CvOUTSIDE> in the I<one specific instance> that the parent
152 has a C<&> pad slot pointing back to us. In this case, we set the
153 C<CvWEAKOUTSIDE> flag in the child. This allows us to determine under what
154 circumstances we should decrement the refcount of the parent when freeing
157 There is a further complication with non-closure anonymous subs (i.e. those
158 that do not refer to any lexicals outside that sub). In this case, the
159 anonymous prototype is shared rather than being cloned. This has the
160 consequence that the parent may be freed while there are still active
163 BEGIN { $a = sub { eval '$x' } }
165 In this case, the BEGIN is freed immediately after execution since there
166 are no active references to it: the anon sub prototype has
167 C<CvWEAKOUTSIDE> set since it's not a closure, and $a points to the same
168 CV, so it doesn't contribute to BEGIN's refcount either. When $a is
169 executed, the C<eval '$x'> causes the chain of C<CvOUTSIDE>s to be followed,
170 and the freed BEGIN is accessed.
172 To avoid this, whenever a CV and its associated pad is freed, any
173 C<&> entries in the pad are explicitly removed from the pad, and if the
174 refcount of the pointed-to anon sub is still positive, then that
175 child's C<CvOUTSIDE> is set to point to its grandparent. This will only
176 occur in the single specific case of a non-closure anon prototype
177 having one or more active references (such as C<$a> above).
179 One other thing to consider is that a CV may be merely undefined
180 rather than freed, eg C<undef &foo>. In this case, its refcount may
181 not have reached zero, but we still delete its pad and its C<CvROOT> etc.
182 Since various children may still have their C<CvOUTSIDE> pointing at this
183 undefined CV, we keep its own C<CvOUTSIDE> for the time being, so that
184 the chain of lexical scopes is unbroken. For example, the following
188 sub tmp { sub { eval '$x' } }
196 typedef OP *(*Perl_call_checker)(pTHX_ OP *, GV *, SV *);
200 * c-indentation-style: bsd
202 * indent-tabs-mode: t
205 * ex: set ts=8 sts=4 sw=4 noet: