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 match 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 This section documents functions to manipulate CVs which are code-values,
29 or subroutines. For more information, see L<perlguts>.
31 =for apidoc Am|HV*|CvSTASH|CV* cv
32 Returns the stash of the CV. A stash is the symbol table hash, containing
33 the package-scoped variables in the package where the subroutine was defined.
34 For more information, see L<perlguts>.
36 This also has a special use with XS AUTOLOAD subs.
37 See L<perlguts/Autoloading with XSUBs>.
43 # define Nullcv Null(CV*)
46 #define CvSTASH(sv) (0+((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_stash)
47 #define CvSTASH_set(cv,st) Perl_cvstash_set(aTHX_ cv, st)
48 #define CvSTART(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_start_u.xcv_start
49 #define CvROOT(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_root_u.xcv_root
50 #define CvXSUB(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_root_u.xcv_xsub
51 #define CvXSUBANY(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_start_u.xcv_xsubany
52 #define CvGV(sv) (0+((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_gv)
53 #define CvGV_set(cv,gv) Perl_cvgv_set(aTHX_ cv, gv)
54 #define CvFILE(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_file
56 # define CvFILE_set_from_cop(sv, cop) \
57 (CvFILE(sv) = savepv(CopFILE(cop)), CvDYNFILE_on(sv))
59 # define CvFILE_set_from_cop(sv, cop) \
60 (CvFILE(sv) = CopFILE(cop), CvDYNFILE_off(sv))
62 #define CvFILEGV(sv) (gv_fetchfile(CvFILE(sv)))
63 #define CvDEPTH(sv) (*S_CvDEPTHp((const CV *)sv))
64 #define CvPADLIST(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_padlist
65 #define CvOUTSIDE(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_outside
66 #define CvFLAGS(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_flags
67 #define CvOUTSIDE_SEQ(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_outside_seq
69 /* These two are sometimes called on non-CVs */
73 ? SvTYPE(sv) == SVt_PVCV && CvAUTOLOAD(sv) \
74 ? SvEND(sv)+1 : SvPVX_const(sv) \
77 #define CvPROTOLEN(sv) \
80 ? SvTYPE(sv) == SVt_PVCV && CvAUTOLOAD(sv) \
81 ? SvLEN(sv)-SvCUR(sv)-2 \
86 #define CVf_METHOD 0x0001 /* CV is explicitly marked as a method */
87 #define CVf_LVALUE 0x0002 /* CV return value can be used as lvalue */
88 #define CVf_CONST 0x0004 /* inlinable sub */
89 #define CVf_ISXSUB 0x0008 /* CV is an XSUB, not pure perl. */
91 #define CVf_WEAKOUTSIDE 0x0010 /* CvOUTSIDE isn't ref counted */
92 #define CVf_CLONE 0x0020 /* anon CV uses external lexicals */
93 #define CVf_CLONED 0x0040 /* a clone of one of those */
94 #define CVf_ANON 0x0080 /* CV is not pointed to by a GV */
95 #define CVf_UNIQUE 0x0100 /* sub is only called once (eg PL_main_cv,
97 #define CVf_NODEBUG 0x0200 /* no DB::sub indirection for this CV
98 (esp. useful for special XSUBs) */
99 #define CVf_CVGV_RC 0x0400 /* CvGV is reference counted */
101 # define CVf_SLABBED 0x0800 /* Holds refcount on op slab */
103 #define CVf_DYNFILE 0x1000 /* The filename isn't static */
104 #define CVf_AUTOLOAD 0x2000 /* SvPVX contains AUTOLOADed sub name */
105 #define CVf_HASEVAL 0x4000 /* contains string eval */
107 /* This symbol for optimised communication between toke.c and op.c: */
108 #define CVf_BUILTIN_ATTRS (CVf_METHOD|CVf_LVALUE)
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 /* CvEVAL or CvSPECIAL */
123 #define CvUNIQUE(cv) (CvFLAGS(cv) & CVf_UNIQUE)
124 #define CvUNIQUE_on(cv) (CvFLAGS(cv) |= CVf_UNIQUE)
125 #define CvUNIQUE_off(cv) (CvFLAGS(cv) &= ~CVf_UNIQUE)
127 #define CvNODEBUG(cv) (CvFLAGS(cv) & CVf_NODEBUG)
128 #define CvNODEBUG_on(cv) (CvFLAGS(cv) |= CVf_NODEBUG)
129 #define CvNODEBUG_off(cv) (CvFLAGS(cv) &= ~CVf_NODEBUG)
131 #define CvMETHOD(cv) (CvFLAGS(cv) & CVf_METHOD)
132 #define CvMETHOD_on(cv) (CvFLAGS(cv) |= CVf_METHOD)
133 #define CvMETHOD_off(cv) (CvFLAGS(cv) &= ~CVf_METHOD)
135 #define CvLVALUE(cv) (CvFLAGS(cv) & CVf_LVALUE)
136 #define CvLVALUE_on(cv) (CvFLAGS(cv) |= CVf_LVALUE)
137 #define CvLVALUE_off(cv) (CvFLAGS(cv) &= ~CVf_LVALUE)
139 /* eval or PL_main_cv */
140 #define CvEVAL(cv) (CvUNIQUE(cv) && !SvFAKE(cv))
141 #define CvEVAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_off(cv))
142 #define CvEVAL_off(cv) CvUNIQUE_off(cv)
144 /* BEGIN|CHECK|INIT|UNITCHECK|END */
145 #define CvSPECIAL(cv) (CvUNIQUE(cv) && SvFAKE(cv))
146 #define CvSPECIAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_on(cv))
147 #define CvSPECIAL_off(cv) (CvUNIQUE_off(cv),SvFAKE_off(cv))
149 #define CvCONST(cv) (CvFLAGS(cv) & CVf_CONST)
150 #define CvCONST_on(cv) (CvFLAGS(cv) |= CVf_CONST)
151 #define CvCONST_off(cv) (CvFLAGS(cv) &= ~CVf_CONST)
153 #define CvWEAKOUTSIDE(cv) (CvFLAGS(cv) & CVf_WEAKOUTSIDE)
154 #define CvWEAKOUTSIDE_on(cv) (CvFLAGS(cv) |= CVf_WEAKOUTSIDE)
155 #define CvWEAKOUTSIDE_off(cv) (CvFLAGS(cv) &= ~CVf_WEAKOUTSIDE)
157 #define CvISXSUB(cv) (CvFLAGS(cv) & CVf_ISXSUB)
158 #define CvISXSUB_on(cv) (CvFLAGS(cv) |= CVf_ISXSUB)
159 #define CvISXSUB_off(cv) (CvFLAGS(cv) &= ~CVf_ISXSUB)
161 #define CvCVGV_RC(cv) (CvFLAGS(cv) & CVf_CVGV_RC)
162 #define CvCVGV_RC_on(cv) (CvFLAGS(cv) |= CVf_CVGV_RC)
163 #define CvCVGV_RC_off(cv) (CvFLAGS(cv) &= ~CVf_CVGV_RC)
166 # define CvSLABBED(cv) (CvFLAGS(cv) & CVf_SLABBED)
167 # define CvSLABBED_on(cv) (CvFLAGS(cv) |= CVf_SLABBED)
168 # define CvSLABBED_off(cv) (CvFLAGS(cv) &= ~CVf_SLABBED)
171 #define CvDYNFILE(cv) (CvFLAGS(cv) & CVf_DYNFILE)
172 #define CvDYNFILE_on(cv) (CvFLAGS(cv) |= CVf_DYNFILE)
173 #define CvDYNFILE_off(cv) (CvFLAGS(cv) &= ~CVf_DYNFILE)
175 #define CvAUTOLOAD(cv) (CvFLAGS(cv) & CVf_AUTOLOAD)
176 #define CvAUTOLOAD_on(cv) (CvFLAGS(cv) |= CVf_AUTOLOAD)
177 #define CvAUTOLOAD_off(cv) (CvFLAGS(cv) &= ~CVf_AUTOLOAD)
179 #define CvHASEVAL(cv) (CvFLAGS(cv) & CVf_HASEVAL)
180 #define CvHASEVAL_on(cv) (CvFLAGS(cv) |= CVf_HASEVAL)
181 #define CvHASEVAL_off(cv) (CvFLAGS(cv) &= ~CVf_HASEVAL)
183 /* Flags for newXS_flags */
184 #define XS_DYNAMIC_FILENAME 0x01 /* The filename isn't static */
187 =head1 CV reference counts and CvOUTSIDE
189 =for apidoc m|bool|CvWEAKOUTSIDE|CV *cv
191 Each CV has a pointer, C<CvOUTSIDE()>, to its lexically enclosing
192 CV (if any). Because pointers to anonymous sub prototypes are
193 stored in C<&> pad slots, it is a possible to get a circular reference,
194 with the parent pointing to the child and vice-versa. To avoid the
195 ensuing memory leak, we do not increment the reference count of the CV
196 pointed to by C<CvOUTSIDE> in the I<one specific instance> that the parent
197 has a C<&> pad slot pointing back to us. In this case, we set the
198 C<CvWEAKOUTSIDE> flag in the child. This allows us to determine under what
199 circumstances we should decrement the refcount of the parent when freeing
202 There is a further complication with non-closure anonymous subs (i.e. those
203 that do not refer to any lexicals outside that sub). In this case, the
204 anonymous prototype is shared rather than being cloned. This has the
205 consequence that the parent may be freed while there are still active
208 BEGIN { $a = sub { eval '$x' } }
210 In this case, the BEGIN is freed immediately after execution since there
211 are no active references to it: the anon sub prototype has
212 C<CvWEAKOUTSIDE> set since it's not a closure, and $a points to the same
213 CV, so it doesn't contribute to BEGIN's refcount either. When $a is
214 executed, the C<eval '$x'> causes the chain of C<CvOUTSIDE>s to be followed,
215 and the freed BEGIN is accessed.
217 To avoid this, whenever a CV and its associated pad is freed, any
218 C<&> entries in the pad are explicitly removed from the pad, and if the
219 refcount of the pointed-to anon sub is still positive, then that
220 child's C<CvOUTSIDE> is set to point to its grandparent. This will only
221 occur in the single specific case of a non-closure anon prototype
222 having one or more active references (such as C<$a> above).
224 One other thing to consider is that a CV may be merely undefined
225 rather than freed, eg C<undef &foo>. In this case, its refcount may
226 not have reached zero, but we still delete its pad and its C<CvROOT> etc.
227 Since various children may still have their C<CvOUTSIDE> pointing at this
228 undefined CV, we keep its own C<CvOUTSIDE> for the time being, so that
229 the chain of lexical scopes is unbroken. For example, the following
233 sub tmp { sub { eval '$x' } }
241 typedef OP *(*Perl_call_checker)(pTHX_ OP *, GV *, SV *);
245 * c-indentation-style: bsd
247 * indent-tabs-mode: nil
250 * ex: set ts=8 sts=4 sw=4 et: