3 * Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1999,
4 * 2000, 2001, 2002, 2003, 2004, 2005, 2006, 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 */
14 NV xnv_nv; /* numeric value, if any */
15 STRLEN xpv_cur; /* length of xp_pv as a C string */
16 STRLEN xpv_len; /* allocated size */
21 I32 xivu_i32; /* depth, >= 2 indicates recursive call */
23 MAGIC* xmg_magic; /* magic for scalar array */
24 HV* xmg_stash; /* class package */
33 void (*xcv_xsub) (pTHX_ CV*);
38 PADLIST * xcv_padlist;
40 U32 xcv_outside_seq; /* the COP sequence (at the point of our
41 * compilation) in the lexically enclosing
49 =for apidoc AmU||Nullcv
52 =head1 CV Manipulation Functions
54 =for apidoc Am|HV*|CvSTASH|CV* cv
55 Returns the stash of the CV.
60 #define Nullcv Null(CV*)
62 #define CvSTASH(sv) ((XPVCV*)SvANY(sv))->xcv_stash
63 #define CvSTART(sv) ((XPVCV*)SvANY(sv))->xcv_start_u.xcv_start
64 #define CvROOT(sv) ((XPVCV*)SvANY(sv))->xcv_root_u.xcv_root
65 #define CvXSUB(sv) ((XPVCV*)SvANY(sv))->xcv_root_u.xcv_xsub
66 #define CvXSUBANY(sv) ((XPVCV*)SvANY(sv))->xcv_start_u.xcv_xsubany
67 #define CvGV(sv) ((XPVCV*)SvANY(sv))->xcv_gv
68 #define CvFILE(sv) ((XPVCV*)SvANY(sv))->xcv_file
70 # define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = savepv(CopFILE(cop)))
72 # define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = CopFILE(cop))
74 #define CvFILEGV(sv) (gv_fetchfile(CvFILE(sv)))
75 #if defined(__GNUC__) && !defined(PERL_GCC_BRACE_GROUPS_FORBIDDEN)
76 # define CvDEPTH(sv) (*({const CV *_cv = (CV *)sv; \
77 assert(SvTYPE(_cv) == SVt_PVCV); \
78 &((XPVCV*)SvANY(_cv))->xiv_u.xivu_i32; \
81 # define CvDEPTH(sv) ((XPVCV*)SvANY(sv))->xiv_u.xivu_i32
83 #define CvPADLIST(sv) ((XPVCV*)SvANY(sv))->xcv_padlist
84 #define CvOUTSIDE(sv) ((XPVCV*)SvANY(sv))->xcv_outside
85 #define CvFLAGS(sv) ((XPVCV*)SvANY(sv))->xcv_flags
86 #define CvOUTSIDE_SEQ(sv) ((XPVCV*)SvANY(sv))->xcv_outside_seq
88 #define CVf_METHOD 0x0001 /* CV is explicitly marked as a method */
89 #define CVf_LOCKED 0x0002 /* CV locks itself or first arg on entry */
90 #define CVf_LVALUE 0x0004 /* CV return value can be used as lvalue */
91 #define CVf_ASSERTION 0x0008 /* CV called only when asserting */
93 #define CVf_WEAKOUTSIDE 0x0010 /* CvOUTSIDE isn't ref counted */
94 #define CVf_CLONE 0x0020 /* anon CV uses external lexicals */
95 #define CVf_CLONED 0x0040 /* a clone of one of those */
96 #define CVf_ANON 0x0080 /* CvGV() can't be trusted */
97 #define CVf_UNIQUE 0x0100 /* sub is only called once (eg PL_main_cv,
98 * require, eval). Not to be confused
99 * with the GVf_UNIQUE flag associated
100 * with the :unique attribute */
101 #define CVf_NODEBUG 0x0200 /* no DB::sub indirection for this CV
102 (esp. useful for special XSUBs) */
103 #define CVf_CONST 0x0400 /* inlinable sub */
104 #define CVf_OLDSTYLE 0x0800
105 #define CVf_ISXSUB 0x1000 /* CV is an XSUB, not pure perl. */
107 /* This symbol for optimised communication between toke.c and op.c: */
108 #define CVf_BUILTIN_ATTRS (CVf_METHOD|CVf_LOCKED|CVf_LVALUE|CVf_ASSERTION)
110 #define CvCLONE(cv) (CvFLAGS(cv) & CVf_CLONE)
111 #define CvCLONE_on(cv) (CvFLAGS(cv) |= CVf_CLONE)
112 #define CvCLONE_off(cv) (CvFLAGS(cv) &= ~CVf_CLONE)
114 #define CvCLONED(cv) (CvFLAGS(cv) & CVf_CLONED)
115 #define CvCLONED_on(cv) (CvFLAGS(cv) |= CVf_CLONED)
116 #define CvCLONED_off(cv) (CvFLAGS(cv) &= ~CVf_CLONED)
118 #define CvANON(cv) (CvFLAGS(cv) & CVf_ANON)
119 #define CvANON_on(cv) (CvFLAGS(cv) |= CVf_ANON)
120 #define CvANON_off(cv) (CvFLAGS(cv) &= ~CVf_ANON)
122 #ifdef PERL_XSUB_OLDSTYLE
123 #define CvOLDSTYLE(cv) (CvFLAGS(cv) & CVf_OLDSTYLE)
124 #define CvOLDSTYLE_on(cv) (CvFLAGS(cv) |= CVf_OLDSTYLE)
125 #define CvOLDSTYLE_off(cv) (CvFLAGS(cv) &= ~CVf_OLDSTYLE)
128 #define CvUNIQUE(cv) (CvFLAGS(cv) & CVf_UNIQUE)
129 #define CvUNIQUE_on(cv) (CvFLAGS(cv) |= CVf_UNIQUE)
130 #define CvUNIQUE_off(cv) (CvFLAGS(cv) &= ~CVf_UNIQUE)
132 #define CvNODEBUG(cv) (CvFLAGS(cv) & CVf_NODEBUG)
133 #define CvNODEBUG_on(cv) (CvFLAGS(cv) |= CVf_NODEBUG)
134 #define CvNODEBUG_off(cv) (CvFLAGS(cv) &= ~CVf_NODEBUG)
136 #define CvMETHOD(cv) (CvFLAGS(cv) & CVf_METHOD)
137 #define CvMETHOD_on(cv) (CvFLAGS(cv) |= CVf_METHOD)
138 #define CvMETHOD_off(cv) (CvFLAGS(cv) &= ~CVf_METHOD)
140 #define CvLOCKED(cv) (CvFLAGS(cv) & CVf_LOCKED)
141 #define CvLOCKED_on(cv) (CvFLAGS(cv) |= CVf_LOCKED)
142 #define CvLOCKED_off(cv) (CvFLAGS(cv) &= ~CVf_LOCKED)
144 #define CvLVALUE(cv) (CvFLAGS(cv) & CVf_LVALUE)
145 #define CvLVALUE_on(cv) (CvFLAGS(cv) |= CVf_LVALUE)
146 #define CvLVALUE_off(cv) (CvFLAGS(cv) &= ~CVf_LVALUE)
148 #define CvASSERTION(cv) (CvFLAGS(cv) & CVf_ASSERTION)
149 #define CvASSERTION_on(cv) (CvFLAGS(cv) |= CVf_ASSERTION)
150 #define CvASSERTION_off(cv) (CvFLAGS(cv) &= ~CVf_ASSERTION)
152 #define CvEVAL(cv) (CvUNIQUE(cv) && !SvFAKE(cv))
153 #define CvEVAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_off(cv))
154 #define CvEVAL_off(cv) CvUNIQUE_off(cv)
156 /* BEGIN|CHECK|INIT|END */
157 #define CvSPECIAL(cv) (CvUNIQUE(cv) && SvFAKE(cv))
158 #define CvSPECIAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_on(cv))
159 #define CvSPECIAL_off(cv) (CvUNIQUE_off(cv),SvFAKE_off(cv))
161 #define CvCONST(cv) (CvFLAGS(cv) & CVf_CONST)
162 #define CvCONST_on(cv) (CvFLAGS(cv) |= CVf_CONST)
163 #define CvCONST_off(cv) (CvFLAGS(cv) &= ~CVf_CONST)
165 #define CvWEAKOUTSIDE(cv) (CvFLAGS(cv) & CVf_WEAKOUTSIDE)
166 #define CvWEAKOUTSIDE_on(cv) (CvFLAGS(cv) |= CVf_WEAKOUTSIDE)
167 #define CvWEAKOUTSIDE_off(cv) (CvFLAGS(cv) &= ~CVf_WEAKOUTSIDE)
169 #define CvISXSUB(cv) (CvFLAGS(cv) & CVf_ISXSUB)
170 #define CvISXSUB_on(cv) (CvFLAGS(cv) |= CVf_ISXSUB)
171 #define CvISXSUB_off(cv) (CvFLAGS(cv) &= ~CVf_ISXSUB)
174 =head1 CV reference counts and CvOUTSIDE
176 =for apidoc m|bool|CvWEAKOUTSIDE|CV *cv
178 Each CV has a pointer, C<CvOUTSIDE()>, to its lexically enclosing
179 CV (if any). Because pointers to anonymous sub prototypes are
180 stored in C<&> pad slots, it is a possible to get a circular reference,
181 with the parent pointing to the child and vice-versa. To avoid the
182 ensuing memory leak, we do not increment the reference count of the CV
183 pointed to by C<CvOUTSIDE> in the I<one specific instance> that the parent
184 has a C<&> pad slot pointing back to us. In this case, we set the
185 C<CvWEAKOUTSIDE> flag in the child. This allows us to determine under what
186 circumstances we should decrement the refcount of the parent when freeing
189 There is a further complication with non-closure anonymous subs (i.e. those
190 that do not refer to any lexicals outside that sub). In this case, the
191 anonymous prototype is shared rather than being cloned. This has the
192 consequence that the parent may be freed while there are still active
195 BEGIN { $a = sub { eval '$x' } }
197 In this case, the BEGIN is freed immediately after execution since there
198 are no active references to it: the anon sub prototype has
199 C<CvWEAKOUTSIDE> set since it's not a closure, and $a points to the same
200 CV, so it doesn't contribute to BEGIN's refcount either. When $a is
201 executed, the C<eval '$x'> causes the chain of C<CvOUTSIDE>s to be followed,
202 and the freed BEGIN is accessed.
204 To avoid this, whenever a CV and its associated pad is freed, any
205 C<&> entries in the pad are explicitly removed from the pad, and if the
206 refcount of the pointed-to anon sub is still positive, then that
207 child's C<CvOUTSIDE> is set to point to its grandparent. This will only
208 occur in the single specific case of a non-closure anon prototype
209 having one or more active references (such as C<$a> above).
211 One other thing to consider is that a CV may be merely undefined
212 rather than freed, eg C<undef &foo>. In this case, its refcount may
213 not have reached zero, but we still delete its pad and its C<CvROOT> etc.
214 Since various children may still have their C<CvOUTSIDE> pointing at this
215 undefined CV, we keep its own C<CvOUTSIDE> for the time being, so that
216 the chain of lexical scopes is unbroken. For example, the following
220 sub tmp { sub { eval '$x' } }
230 * c-indentation-style: bsd
232 * indent-tabs-mode: t
235 * ex: set ts=8 sts=4 sw=4 noet: