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 */
21 =for apidoc AmU||Nullcv
24 (deprecated - use C<(CV *)NULL> instead)
26 =head1 CV Manipulation Functions
28 =for apidoc Am|HV*|CvSTASH|CV* cv
29 Returns the stash of the CV.
35 # define Nullcv Null(CV*)
38 #define CvSTASH(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_stash
39 #define CvSTART(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_start_u.xcv_start
40 #define CvROOT(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_root_u.xcv_root
41 #define CvXSUB(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_root_u.xcv_xsub
42 #define CvXSUBANY(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_start_u.xcv_xsubany
43 #define CvGV(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_gv
44 #define CvFILE(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_file
46 # define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = savepv(CopFILE(cop)))
48 # define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = CopFILE(cop))
50 #define CvFILEGV(sv) (gv_fetchfile(CvFILE(sv)))
51 #if defined(__GNUC__) && !defined(PERL_GCC_BRACE_GROUPS_FORBIDDEN)
52 # define CvDEPTH(sv) (*({const CV *const _cvdepth = (const CV *)sv; \
53 assert(SvTYPE(_cvdepth) == SVt_PVCV); \
54 &((XPVCV*)SvANY(_cvdepth))->xiv_u.xivu_i32; \
57 # define CvDEPTH(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xiv_u.xivu_i32
59 #define CvPADLIST(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_padlist
60 #define CvOUTSIDE(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_outside
61 #define CvFLAGS(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_flags
62 #define CvOUTSIDE_SEQ(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_outside_seq
64 #define CVf_METHOD 0x0001 /* CV is explicitly marked as a method */
65 #define CVf_LVALUE 0x0004 /* CV return value can be used as lvalue */
67 #define CVf_WEAKOUTSIDE 0x0010 /* CvOUTSIDE isn't ref counted */
68 #define CVf_CLONE 0x0020 /* anon CV uses external lexicals */
69 #define CVf_CLONED 0x0040 /* a clone of one of those */
70 #define CVf_ANON 0x0080 /* CvGV() can't be trusted */
71 #define CVf_UNIQUE 0x0100 /* sub is only called once (eg PL_main_cv,
73 #define CVf_NODEBUG 0x0200 /* no DB::sub indirection for this CV
74 (esp. useful for special XSUBs) */
75 #define CVf_CONST 0x0400 /* inlinable sub */
76 #define CVf_ISXSUB 0x0800 /* CV is an XSUB, not pure perl. */
78 /* This symbol for optimised communication between toke.c and op.c: */
79 #define CVf_BUILTIN_ATTRS (CVf_METHOD|CVf_LVALUE)
81 #define CvCLONE(cv) (CvFLAGS(cv) & CVf_CLONE)
82 #define CvCLONE_on(cv) (CvFLAGS(cv) |= CVf_CLONE)
83 #define CvCLONE_off(cv) (CvFLAGS(cv) &= ~CVf_CLONE)
85 #define CvCLONED(cv) (CvFLAGS(cv) & CVf_CLONED)
86 #define CvCLONED_on(cv) (CvFLAGS(cv) |= CVf_CLONED)
87 #define CvCLONED_off(cv) (CvFLAGS(cv) &= ~CVf_CLONED)
89 #define CvANON(cv) (CvFLAGS(cv) & CVf_ANON)
90 #define CvANON_on(cv) (CvFLAGS(cv) |= CVf_ANON)
91 #define CvANON_off(cv) (CvFLAGS(cv) &= ~CVf_ANON)
93 #define CvUNIQUE(cv) (CvFLAGS(cv) & CVf_UNIQUE)
94 #define CvUNIQUE_on(cv) (CvFLAGS(cv) |= CVf_UNIQUE)
95 #define CvUNIQUE_off(cv) (CvFLAGS(cv) &= ~CVf_UNIQUE)
97 #define CvNODEBUG(cv) (CvFLAGS(cv) & CVf_NODEBUG)
98 #define CvNODEBUG_on(cv) (CvFLAGS(cv) |= CVf_NODEBUG)
99 #define CvNODEBUG_off(cv) (CvFLAGS(cv) &= ~CVf_NODEBUG)
101 #define CvMETHOD(cv) (CvFLAGS(cv) & CVf_METHOD)
102 #define CvMETHOD_on(cv) (CvFLAGS(cv) |= CVf_METHOD)
103 #define CvMETHOD_off(cv) (CvFLAGS(cv) &= ~CVf_METHOD)
105 #define CvLVALUE(cv) (CvFLAGS(cv) & CVf_LVALUE)
106 #define CvLVALUE_on(cv) (CvFLAGS(cv) |= CVf_LVALUE)
107 #define CvLVALUE_off(cv) (CvFLAGS(cv) &= ~CVf_LVALUE)
109 #define CvEVAL(cv) (CvUNIQUE(cv) && !SvFAKE(cv))
110 #define CvEVAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_off(cv))
111 #define CvEVAL_off(cv) CvUNIQUE_off(cv)
113 /* BEGIN|CHECK|INIT|UNITCHECK|END */
114 #define CvSPECIAL(cv) (CvUNIQUE(cv) && SvFAKE(cv))
115 #define CvSPECIAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_on(cv))
116 #define CvSPECIAL_off(cv) (CvUNIQUE_off(cv),SvFAKE_off(cv))
118 #define CvCONST(cv) (CvFLAGS(cv) & CVf_CONST)
119 #define CvCONST_on(cv) (CvFLAGS(cv) |= CVf_CONST)
120 #define CvCONST_off(cv) (CvFLAGS(cv) &= ~CVf_CONST)
122 #define CvWEAKOUTSIDE(cv) (CvFLAGS(cv) & CVf_WEAKOUTSIDE)
123 #define CvWEAKOUTSIDE_on(cv) (CvFLAGS(cv) |= CVf_WEAKOUTSIDE)
124 #define CvWEAKOUTSIDE_off(cv) (CvFLAGS(cv) &= ~CVf_WEAKOUTSIDE)
126 #define CvISXSUB(cv) (CvFLAGS(cv) & CVf_ISXSUB)
127 #define CvISXSUB_on(cv) (CvFLAGS(cv) |= CVf_ISXSUB)
128 #define CvISXSUB_off(cv) (CvFLAGS(cv) &= ~CVf_ISXSUB)
130 /* Flags for newXS_flags */
131 #define XS_DYNAMIC_FILENAME 0x01 /* The filename isn't static */
134 =head1 CV reference counts and CvOUTSIDE
136 =for apidoc m|bool|CvWEAKOUTSIDE|CV *cv
138 Each CV has a pointer, C<CvOUTSIDE()>, to its lexically enclosing
139 CV (if any). Because pointers to anonymous sub prototypes are
140 stored in C<&> pad slots, it is a possible to get a circular reference,
141 with the parent pointing to the child and vice-versa. To avoid the
142 ensuing memory leak, we do not increment the reference count of the CV
143 pointed to by C<CvOUTSIDE> in the I<one specific instance> that the parent
144 has a C<&> pad slot pointing back to us. In this case, we set the
145 C<CvWEAKOUTSIDE> flag in the child. This allows us to determine under what
146 circumstances we should decrement the refcount of the parent when freeing
149 There is a further complication with non-closure anonymous subs (i.e. those
150 that do not refer to any lexicals outside that sub). In this case, the
151 anonymous prototype is shared rather than being cloned. This has the
152 consequence that the parent may be freed while there are still active
155 BEGIN { $a = sub { eval '$x' } }
157 In this case, the BEGIN is freed immediately after execution since there
158 are no active references to it: the anon sub prototype has
159 C<CvWEAKOUTSIDE> set since it's not a closure, and $a points to the same
160 CV, so it doesn't contribute to BEGIN's refcount either. When $a is
161 executed, the C<eval '$x'> causes the chain of C<CvOUTSIDE>s to be followed,
162 and the freed BEGIN is accessed.
164 To avoid this, whenever a CV and its associated pad is freed, any
165 C<&> entries in the pad are explicitly removed from the pad, and if the
166 refcount of the pointed-to anon sub is still positive, then that
167 child's C<CvOUTSIDE> is set to point to its grandparent. This will only
168 occur in the single specific case of a non-closure anon prototype
169 having one or more active references (such as C<$a> above).
171 One other thing to consider is that a CV may be merely undefined
172 rather than freed, eg C<undef &foo>. In this case, its refcount may
173 not have reached zero, but we still delete its pad and its C<CvROOT> etc.
174 Since various children may still have their C<CvOUTSIDE> pointing at this
175 undefined CV, we keep its own C<CvOUTSIDE> for the time being, so that
176 the chain of lexical scopes is unbroken. For example, the following
180 sub tmp { sub { eval '$x' } }
190 * c-indentation-style: bsd
192 * indent-tabs-mode: t
195 * ex: set ts=8 sts=4 sw=4 noet: