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