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add CVf_CVGV_RC flag
[perl5.git] / cv.h
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a0d0e21e 1/* cv.h
79072805 2 *
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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
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5 *
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.
8 *
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9 */
10
7c60e434 11/* This structure must the beginning of XPVFM in sv.h */
44a8e56a 12
79072805 13struct xpvcv {
20f4945e 14 _XPV_HEAD;
20f4945e 15 _XPVCV_COMMON;
c4648999 16 I32 xcv_depth; /* >= 2 indicates recursive call */
79072805 17};
748a9306 18
954c1994 19/*
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20=head1 Handy Values
21
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22=for apidoc AmU||Nullcv
23Null CV pointer.
24
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25(deprecated - use C<(CV *)NULL> instead)
26
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27=head1 CV Manipulation Functions
28
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29=for apidoc Am|HV*|CvSTASH|CV* cv
30Returns the stash of the CV.
31
32=cut
33*/
34
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35#ifndef PERL_CORE
36# define Nullcv Null(CV*)
37#endif
a5f75d66 38
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39#define CvSTASH(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_stash
40#define CvSTART(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_start_u.xcv_start
41#define CvROOT(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_root_u.xcv_root
42#define CvXSUB(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_root_u.xcv_xsub
43#define CvXSUBANY(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_start_u.xcv_xsubany
44#define CvGV(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_gv
45#define CvFILE(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_file
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46#ifdef USE_ITHREADS
47# define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = savepv(CopFILE(cop)))
48#else
49# define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = CopFILE(cop))
50#endif
9ec2a764 51#define CvFILEGV(sv) (gv_fetchfile(CvFILE(sv)))
bb172083 52#if defined(__GNUC__) && !defined(PERL_GCC_BRACE_GROUPS_FORBIDDEN)
8f629a87 53# define CvDEPTH(sv) (*({const CV *const _cvdepth = (const CV *)sv; \
5129b2ca 54 assert(SvTYPE(_cvdepth) == SVt_PVCV); \
c4648999 55 &((XPVCV*)SvANY(_cvdepth))->xcv_depth; \
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56 }))
57#else
c4648999 58# define CvDEPTH(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_depth
bb172083 59#endif
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60#define CvPADLIST(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_padlist
61#define CvOUTSIDE(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_outside
62#define CvFLAGS(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_flags
63#define CvOUTSIDE_SEQ(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_outside_seq
a5f75d66 64
5b4563c8 65#define CVf_METHOD 0x0001 /* CV is explicitly marked as a method */
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66#define CVf_LVALUE 0x0002 /* CV return value can be used as lvalue */
67#define CVf_CONST 0x0004 /* inlinable sub */
68#define CVf_ISXSUB 0x0008 /* CV is an XSUB, not pure perl. */
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69
70#define CVf_WEAKOUTSIDE 0x0010 /* CvOUTSIDE isn't ref counted */
71#define CVf_CLONE 0x0020 /* anon CV uses external lexicals */
72#define CVf_CLONED 0x0040 /* a clone of one of those */
cfc1e951 73#define CVf_ANON 0x0080 /* CV is not pointed to by a GV */
5b4563c8 74#define CVf_UNIQUE 0x0100 /* sub is only called once (eg PL_main_cv,
1108974d 75 * require, eval). */
5b4563c8 76#define CVf_NODEBUG 0x0200 /* no DB::sub indirection for this CV
8ebc5c01 77 (esp. useful for special XSUBs) */
cfc1e951 78#define CVf_CVGV_RC 0x0400 /* CvGV is reference counted */
7dafbf52 79
d3cea301 80/* This symbol for optimised communication between toke.c and op.c: */
e95ab0c0 81#define CVf_BUILTIN_ATTRS (CVf_METHOD|CVf_LVALUE)
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82
83#define CvCLONE(cv) (CvFLAGS(cv) & CVf_CLONE)
84#define CvCLONE_on(cv) (CvFLAGS(cv) |= CVf_CLONE)
85#define CvCLONE_off(cv) (CvFLAGS(cv) &= ~CVf_CLONE)
86
87#define CvCLONED(cv) (CvFLAGS(cv) & CVf_CLONED)
88#define CvCLONED_on(cv) (CvFLAGS(cv) |= CVf_CLONED)
89#define CvCLONED_off(cv) (CvFLAGS(cv) &= ~CVf_CLONED)
90
91#define CvANON(cv) (CvFLAGS(cv) & CVf_ANON)
92#define CvANON_on(cv) (CvFLAGS(cv) |= CVf_ANON)
93#define CvANON_off(cv) (CvFLAGS(cv) &= ~CVf_ANON)
79072805 94
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95#define CvUNIQUE(cv) (CvFLAGS(cv) & CVf_UNIQUE)
96#define CvUNIQUE_on(cv) (CvFLAGS(cv) |= CVf_UNIQUE)
97#define CvUNIQUE_off(cv) (CvFLAGS(cv) &= ~CVf_UNIQUE)
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98
99#define CvNODEBUG(cv) (CvFLAGS(cv) & CVf_NODEBUG)
100#define CvNODEBUG_on(cv) (CvFLAGS(cv) |= CVf_NODEBUG)
101#define CvNODEBUG_off(cv) (CvFLAGS(cv) &= ~CVf_NODEBUG)
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102
103#define CvMETHOD(cv) (CvFLAGS(cv) & CVf_METHOD)
104#define CvMETHOD_on(cv) (CvFLAGS(cv) |= CVf_METHOD)
105#define CvMETHOD_off(cv) (CvFLAGS(cv) &= ~CVf_METHOD)
106
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107#define CvLVALUE(cv) (CvFLAGS(cv) & CVf_LVALUE)
108#define CvLVALUE_on(cv) (CvFLAGS(cv) |= CVf_LVALUE)
109#define CvLVALUE_off(cv) (CvFLAGS(cv) &= ~CVf_LVALUE)
110
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111#define CvEVAL(cv) (CvUNIQUE(cv) && !SvFAKE(cv))
112#define CvEVAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_off(cv))
113#define CvEVAL_off(cv) CvUNIQUE_off(cv)
114
3c10abe3 115/* BEGIN|CHECK|INIT|UNITCHECK|END */
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116#define CvSPECIAL(cv) (CvUNIQUE(cv) && SvFAKE(cv))
117#define CvSPECIAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_on(cv))
118#define CvSPECIAL_off(cv) (CvUNIQUE_off(cv),SvFAKE_off(cv))
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119
120#define CvCONST(cv) (CvFLAGS(cv) & CVf_CONST)
121#define CvCONST_on(cv) (CvFLAGS(cv) |= CVf_CONST)
122#define CvCONST_off(cv) (CvFLAGS(cv) &= ~CVf_CONST)
a4f1a029 123
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124#define CvWEAKOUTSIDE(cv) (CvFLAGS(cv) & CVf_WEAKOUTSIDE)
125#define CvWEAKOUTSIDE_on(cv) (CvFLAGS(cv) |= CVf_WEAKOUTSIDE)
126#define CvWEAKOUTSIDE_off(cv) (CvFLAGS(cv) &= ~CVf_WEAKOUTSIDE)
127
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128#define CvISXSUB(cv) (CvFLAGS(cv) & CVf_ISXSUB)
129#define CvISXSUB_on(cv) (CvFLAGS(cv) |= CVf_ISXSUB)
130#define CvISXSUB_off(cv) (CvFLAGS(cv) &= ~CVf_ISXSUB)
131
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132#define CvCVGV_RC(cv) (CvFLAGS(cv) & CVf_CVGV_RC)
133#define CvCVGV_RC_on(cv) (CvFLAGS(cv) |= CVf_CVGV_RC)
134#define CvCVGV_RC_off(cv) (CvFLAGS(cv) &= ~CVf_CVGV_RC)
135
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136/* Flags for newXS_flags */
137#define XS_DYNAMIC_FILENAME 0x01 /* The filename isn't static */
138
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139/*
140=head1 CV reference counts and CvOUTSIDE
141
142=for apidoc m|bool|CvWEAKOUTSIDE|CV *cv
143
144Each CV has a pointer, C<CvOUTSIDE()>, to its lexically enclosing
145CV (if any). Because pointers to anonymous sub prototypes are
146stored in C<&> pad slots, it is a possible to get a circular reference,
147with the parent pointing to the child and vice-versa. To avoid the
148ensuing memory leak, we do not increment the reference count of the CV
149pointed to by C<CvOUTSIDE> in the I<one specific instance> that the parent
150has a C<&> pad slot pointing back to us. In this case, we set the
151C<CvWEAKOUTSIDE> flag in the child. This allows us to determine under what
152circumstances we should decrement the refcount of the parent when freeing
153the child.
154
eeb8d49e 155There is a further complication with non-closure anonymous subs (i.e. those
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156that do not refer to any lexicals outside that sub). In this case, the
157anonymous prototype is shared rather than being cloned. This has the
158consequence that the parent may be freed while there are still active
159children, eg
160
161 BEGIN { $a = sub { eval '$x' } }
162
163In this case, the BEGIN is freed immediately after execution since there
164are no active references to it: the anon sub prototype has
165C<CvWEAKOUTSIDE> set since it's not a closure, and $a points to the same
166CV, so it doesn't contribute to BEGIN's refcount either. When $a is
167executed, the C<eval '$x'> causes the chain of C<CvOUTSIDE>s to be followed,
168and the freed BEGIN is accessed.
169
170To avoid this, whenever a CV and its associated pad is freed, any
171C<&> entries in the pad are explicitly removed from the pad, and if the
172refcount of the pointed-to anon sub is still positive, then that
173child's C<CvOUTSIDE> is set to point to its grandparent. This will only
174occur in the single specific case of a non-closure anon prototype
175having one or more active references (such as C<$a> above).
176
177One other thing to consider is that a CV may be merely undefined
178rather than freed, eg C<undef &foo>. In this case, its refcount may
179not have reached zero, but we still delete its pad and its C<CvROOT> etc.
180Since various children may still have their C<CvOUTSIDE> pointing at this
181undefined CV, we keep its own C<CvOUTSIDE> for the time being, so that
182the chain of lexical scopes is unbroken. For example, the following
183should print 123:
184
185 my $x = 123;
186 sub tmp { sub { eval '$x' } }
187 my $a = tmp();
188 undef &tmp;
189 print $a->();
190
191=cut
192*/
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193
194/*
195 * Local variables:
196 * c-indentation-style: bsd
197 * c-basic-offset: 4
198 * indent-tabs-mode: t
199 * End:
200 *
201 * ex: set ts=8 sts=4 sw=4 noet:
202 */