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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 {
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14 _XPV_HEAD;
15 _XPVMG_HEAD;
16 _XPVCV_COMMON;
79072805 17};
748a9306 18
c84c4652 19typedef struct {
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20 _XPV_ALLOCATED_HEAD;
21 _XPVMG_HEAD;
22 _XPVCV_COMMON;
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23} xpvcv_allocated;
24
954c1994 25/*
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26=head1 Handy Values
27
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28=for apidoc AmU||Nullcv
29Null CV pointer.
30
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31(deprecated - use C<(CV *)NULL> instead)
32
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33=head1 CV Manipulation Functions
34
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35=for apidoc Am|HV*|CvSTASH|CV* cv
36Returns the stash of the CV.
37
38=cut
39*/
40
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41#ifndef PERL_CORE
42# define Nullcv Null(CV*)
43#endif
a5f75d66 44
79072805 45#define CvSTASH(sv) ((XPVCV*)SvANY(sv))->xcv_stash
bf53b3a5 46#define CvSTART(sv) ((XPVCV*)SvANY(sv))->xcv_start_u.xcv_start
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47#define CvROOT(sv) ((XPVCV*)SvANY(sv))->xcv_root_u.xcv_root
48#define CvXSUB(sv) ((XPVCV*)SvANY(sv))->xcv_root_u.xcv_xsub
bf53b3a5 49#define CvXSUBANY(sv) ((XPVCV*)SvANY(sv))->xcv_start_u.xcv_xsubany
8990e307 50#define CvGV(sv) ((XPVCV*)SvANY(sv))->xcv_gv
57843af0 51#define CvFILE(sv) ((XPVCV*)SvANY(sv))->xcv_file
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52#ifdef USE_ITHREADS
53# define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = savepv(CopFILE(cop)))
54#else
55# define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = CopFILE(cop))
56#endif
9ec2a764 57#define CvFILEGV(sv) (gv_fetchfile(CvFILE(sv)))
bb172083 58#if defined(__GNUC__) && !defined(PERL_GCC_BRACE_GROUPS_FORBIDDEN)
7948fc08 59# define CvDEPTH(sv) (*({const CV *_cvdepth = (CV *)sv; \
5129b2ca 60 assert(SvTYPE(_cvdepth) == SVt_PVCV); \
7948fc08 61 &((XPVCV*)SvANY(_cvdepth))->xiv_u.xivu_i32; \
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62 }))
63#else
64# define CvDEPTH(sv) ((XPVCV*)SvANY(sv))->xiv_u.xivu_i32
65#endif
79072805 66#define CvPADLIST(sv) ((XPVCV*)SvANY(sv))->xcv_padlist
748a9306 67#define CvOUTSIDE(sv) ((XPVCV*)SvANY(sv))->xcv_outside
a5f75d66 68#define CvFLAGS(sv) ((XPVCV*)SvANY(sv))->xcv_flags
a3985cdc 69#define CvOUTSIDE_SEQ(sv) ((XPVCV*)SvANY(sv))->xcv_outside_seq
a5f75d66 70
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71#define CVf_METHOD 0x0001 /* CV is explicitly marked as a method */
72#define CVf_LOCKED 0x0002 /* CV locks itself or first arg on entry */
73#define CVf_LVALUE 0x0004 /* CV return value can be used as lvalue */
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74
75#define CVf_WEAKOUTSIDE 0x0010 /* CvOUTSIDE isn't ref counted */
76#define CVf_CLONE 0x0020 /* anon CV uses external lexicals */
77#define CVf_CLONED 0x0040 /* a clone of one of those */
78#define CVf_ANON 0x0080 /* CvGV() can't be trusted */
79#define CVf_UNIQUE 0x0100 /* sub is only called once (eg PL_main_cv,
1108974d 80 * require, eval). */
5b4563c8 81#define CVf_NODEBUG 0x0200 /* no DB::sub indirection for this CV
8ebc5c01 82 (esp. useful for special XSUBs) */
5b4563c8 83#define CVf_CONST 0x0400 /* inlinable sub */
f73ef291 84#define CVf_ISXSUB 0x0800 /* CV is an XSUB, not pure perl. */
7dafbf52 85
d3cea301 86/* This symbol for optimised communication between toke.c and op.c: */
584420f0 87#define CVf_BUILTIN_ATTRS (CVf_METHOD|CVf_LOCKED|CVf_LVALUE)
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88
89#define CvCLONE(cv) (CvFLAGS(cv) & CVf_CLONE)
90#define CvCLONE_on(cv) (CvFLAGS(cv) |= CVf_CLONE)
91#define CvCLONE_off(cv) (CvFLAGS(cv) &= ~CVf_CLONE)
92
93#define CvCLONED(cv) (CvFLAGS(cv) & CVf_CLONED)
94#define CvCLONED_on(cv) (CvFLAGS(cv) |= CVf_CLONED)
95#define CvCLONED_off(cv) (CvFLAGS(cv) &= ~CVf_CLONED)
96
97#define CvANON(cv) (CvFLAGS(cv) & CVf_ANON)
98#define CvANON_on(cv) (CvFLAGS(cv) |= CVf_ANON)
99#define CvANON_off(cv) (CvFLAGS(cv) &= ~CVf_ANON)
79072805 100
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101#define CvUNIQUE(cv) (CvFLAGS(cv) & CVf_UNIQUE)
102#define CvUNIQUE_on(cv) (CvFLAGS(cv) |= CVf_UNIQUE)
103#define CvUNIQUE_off(cv) (CvFLAGS(cv) &= ~CVf_UNIQUE)
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104
105#define CvNODEBUG(cv) (CvFLAGS(cv) & CVf_NODEBUG)
106#define CvNODEBUG_on(cv) (CvFLAGS(cv) |= CVf_NODEBUG)
107#define CvNODEBUG_off(cv) (CvFLAGS(cv) &= ~CVf_NODEBUG)
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108
109#define CvMETHOD(cv) (CvFLAGS(cv) & CVf_METHOD)
110#define CvMETHOD_on(cv) (CvFLAGS(cv) |= CVf_METHOD)
111#define CvMETHOD_off(cv) (CvFLAGS(cv) &= ~CVf_METHOD)
112
113#define CvLOCKED(cv) (CvFLAGS(cv) & CVf_LOCKED)
114#define CvLOCKED_on(cv) (CvFLAGS(cv) |= CVf_LOCKED)
115#define CvLOCKED_off(cv) (CvFLAGS(cv) &= ~CVf_LOCKED)
1aff0e91 116
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117#define CvLVALUE(cv) (CvFLAGS(cv) & CVf_LVALUE)
118#define CvLVALUE_on(cv) (CvFLAGS(cv) |= CVf_LVALUE)
119#define CvLVALUE_off(cv) (CvFLAGS(cv) &= ~CVf_LVALUE)
120
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121#define CvEVAL(cv) (CvUNIQUE(cv) && !SvFAKE(cv))
122#define CvEVAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_off(cv))
123#define CvEVAL_off(cv) CvUNIQUE_off(cv)
124
3c10abe3 125/* BEGIN|CHECK|INIT|UNITCHECK|END */
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126#define CvSPECIAL(cv) (CvUNIQUE(cv) && SvFAKE(cv))
127#define CvSPECIAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_on(cv))
128#define CvSPECIAL_off(cv) (CvUNIQUE_off(cv),SvFAKE_off(cv))
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129
130#define CvCONST(cv) (CvFLAGS(cv) & CVf_CONST)
131#define CvCONST_on(cv) (CvFLAGS(cv) |= CVf_CONST)
132#define CvCONST_off(cv) (CvFLAGS(cv) &= ~CVf_CONST)
a4f1a029 133
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134#define CvWEAKOUTSIDE(cv) (CvFLAGS(cv) & CVf_WEAKOUTSIDE)
135#define CvWEAKOUTSIDE_on(cv) (CvFLAGS(cv) |= CVf_WEAKOUTSIDE)
136#define CvWEAKOUTSIDE_off(cv) (CvFLAGS(cv) &= ~CVf_WEAKOUTSIDE)
137
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138#define CvISXSUB(cv) (CvFLAGS(cv) & CVf_ISXSUB)
139#define CvISXSUB_on(cv) (CvFLAGS(cv) |= CVf_ISXSUB)
140#define CvISXSUB_off(cv) (CvFLAGS(cv) &= ~CVf_ISXSUB)
141
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142/* Flags for newXS_flags */
143#define XS_DYNAMIC_FILENAME 0x01 /* The filename isn't static */
144
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145/*
146=head1 CV reference counts and CvOUTSIDE
147
148=for apidoc m|bool|CvWEAKOUTSIDE|CV *cv
149
150Each CV has a pointer, C<CvOUTSIDE()>, to its lexically enclosing
151CV (if any). Because pointers to anonymous sub prototypes are
152stored in C<&> pad slots, it is a possible to get a circular reference,
153with the parent pointing to the child and vice-versa. To avoid the
154ensuing memory leak, we do not increment the reference count of the CV
155pointed to by C<CvOUTSIDE> in the I<one specific instance> that the parent
156has a C<&> pad slot pointing back to us. In this case, we set the
157C<CvWEAKOUTSIDE> flag in the child. This allows us to determine under what
158circumstances we should decrement the refcount of the parent when freeing
159the child.
160
eeb8d49e 161There is a further complication with non-closure anonymous subs (i.e. those
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162that do not refer to any lexicals outside that sub). In this case, the
163anonymous prototype is shared rather than being cloned. This has the
164consequence that the parent may be freed while there are still active
165children, eg
166
167 BEGIN { $a = sub { eval '$x' } }
168
169In this case, the BEGIN is freed immediately after execution since there
170are no active references to it: the anon sub prototype has
171C<CvWEAKOUTSIDE> set since it's not a closure, and $a points to the same
172CV, so it doesn't contribute to BEGIN's refcount either. When $a is
173executed, the C<eval '$x'> causes the chain of C<CvOUTSIDE>s to be followed,
174and the freed BEGIN is accessed.
175
176To avoid this, whenever a CV and its associated pad is freed, any
177C<&> entries in the pad are explicitly removed from the pad, and if the
178refcount of the pointed-to anon sub is still positive, then that
179child's C<CvOUTSIDE> is set to point to its grandparent. This will only
180occur in the single specific case of a non-closure anon prototype
181having one or more active references (such as C<$a> above).
182
183One other thing to consider is that a CV may be merely undefined
184rather than freed, eg C<undef &foo>. In this case, its refcount may
185not have reached zero, but we still delete its pad and its C<CvROOT> etc.
186Since various children may still have their C<CvOUTSIDE> pointing at this
187undefined CV, we keep its own C<CvOUTSIDE> for the time being, so that
188the chain of lexical scopes is unbroken. For example, the following
189should print 123:
190
191 my $x = 123;
192 sub tmp { sub { eval '$x' } }
193 my $a = tmp();
194 undef &tmp;
195 print $a->();
196
197=cut
198*/
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199
200/*
201 * Local variables:
202 * c-indentation-style: bsd
203 * c-basic-offset: 4
204 * indent-tabs-mode: t
205 * End:
206 *
207 * ex: set ts=8 sts=4 sw=4 noet:
208 */