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factor out duplicate code in struct xpv*
[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,
4 * 2001, 2002, 2003, 2004, 2005, 2006, 2007, 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=head1 CV Manipulation Functions
32
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33=for apidoc Am|HV*|CvSTASH|CV* cv
34Returns the stash of the CV.
35
36=cut
37*/
38
79072805 39#define Nullcv Null(CV*)
a5f75d66 40
79072805 41#define CvSTASH(sv) ((XPVCV*)SvANY(sv))->xcv_stash
bf53b3a5 42#define CvSTART(sv) ((XPVCV*)SvANY(sv))->xcv_start_u.xcv_start
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43#define CvROOT(sv) ((XPVCV*)SvANY(sv))->xcv_root_u.xcv_root
44#define CvXSUB(sv) ((XPVCV*)SvANY(sv))->xcv_root_u.xcv_xsub
bf53b3a5 45#define CvXSUBANY(sv) ((XPVCV*)SvANY(sv))->xcv_start_u.xcv_xsubany
8990e307 46#define CvGV(sv) ((XPVCV*)SvANY(sv))->xcv_gv
57843af0 47#define CvFILE(sv) ((XPVCV*)SvANY(sv))->xcv_file
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48#ifdef USE_ITHREADS
49# define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = savepv(CopFILE(cop)))
50#else
51# define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = CopFILE(cop))
52#endif
9ec2a764 53#define CvFILEGV(sv) (gv_fetchfile(CvFILE(sv)))
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54#if defined(__GNUC__) && !defined(PERL_GCC_BRACE_GROUPS_FORBIDDEN)
55# define CvDEPTH(sv) (*({const CV *_cv = (CV *)sv; \
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56 assert(SvTYPE(_cv) == SVt_PVCV || \
57 SvTYPE(_cv) == SVt_PVFM); \
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58 &((XPVCV*)SvANY(_cv))->xiv_u.xivu_i32; \
59 }))
60#else
61# define CvDEPTH(sv) ((XPVCV*)SvANY(sv))->xiv_u.xivu_i32
62#endif
79072805 63#define CvPADLIST(sv) ((XPVCV*)SvANY(sv))->xcv_padlist
748a9306 64#define CvOUTSIDE(sv) ((XPVCV*)SvANY(sv))->xcv_outside
a5f75d66 65#define CvFLAGS(sv) ((XPVCV*)SvANY(sv))->xcv_flags
a3985cdc 66#define CvOUTSIDE_SEQ(sv) ((XPVCV*)SvANY(sv))->xcv_outside_seq
a5f75d66 67
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68#define CVf_METHOD 0x0001 /* CV is explicitly marked as a method */
69#define CVf_LOCKED 0x0002 /* CV locks itself or first arg on entry */
70#define CVf_LVALUE 0x0004 /* CV return value can be used as lvalue */
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71
72#define CVf_WEAKOUTSIDE 0x0010 /* CvOUTSIDE isn't ref counted */
73#define CVf_CLONE 0x0020 /* anon CV uses external lexicals */
74#define CVf_CLONED 0x0040 /* a clone of one of those */
75#define CVf_ANON 0x0080 /* CvGV() can't be trusted */
76#define CVf_UNIQUE 0x0100 /* sub is only called once (eg PL_main_cv,
1108974d 77 * require, eval). */
5b4563c8 78#define CVf_NODEBUG 0x0200 /* no DB::sub indirection for this CV
8ebc5c01 79 (esp. useful for special XSUBs) */
5b4563c8 80#define CVf_CONST 0x0400 /* inlinable sub */
f73ef291 81#define CVf_ISXSUB 0x0800 /* CV is an XSUB, not pure perl. */
7dafbf52 82
d3cea301 83/* This symbol for optimised communication between toke.c and op.c: */
584420f0 84#define CVf_BUILTIN_ATTRS (CVf_METHOD|CVf_LOCKED|CVf_LVALUE)
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85
86#define CvCLONE(cv) (CvFLAGS(cv) & CVf_CLONE)
87#define CvCLONE_on(cv) (CvFLAGS(cv) |= CVf_CLONE)
88#define CvCLONE_off(cv) (CvFLAGS(cv) &= ~CVf_CLONE)
89
90#define CvCLONED(cv) (CvFLAGS(cv) & CVf_CLONED)
91#define CvCLONED_on(cv) (CvFLAGS(cv) |= CVf_CLONED)
92#define CvCLONED_off(cv) (CvFLAGS(cv) &= ~CVf_CLONED)
93
94#define CvANON(cv) (CvFLAGS(cv) & CVf_ANON)
95#define CvANON_on(cv) (CvFLAGS(cv) |= CVf_ANON)
96#define CvANON_off(cv) (CvFLAGS(cv) &= ~CVf_ANON)
79072805 97
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98#define CvUNIQUE(cv) (CvFLAGS(cv) & CVf_UNIQUE)
99#define CvUNIQUE_on(cv) (CvFLAGS(cv) |= CVf_UNIQUE)
100#define CvUNIQUE_off(cv) (CvFLAGS(cv) &= ~CVf_UNIQUE)
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101
102#define CvNODEBUG(cv) (CvFLAGS(cv) & CVf_NODEBUG)
103#define CvNODEBUG_on(cv) (CvFLAGS(cv) |= CVf_NODEBUG)
104#define CvNODEBUG_off(cv) (CvFLAGS(cv) &= ~CVf_NODEBUG)
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105
106#define CvMETHOD(cv) (CvFLAGS(cv) & CVf_METHOD)
107#define CvMETHOD_on(cv) (CvFLAGS(cv) |= CVf_METHOD)
108#define CvMETHOD_off(cv) (CvFLAGS(cv) &= ~CVf_METHOD)
109
110#define CvLOCKED(cv) (CvFLAGS(cv) & CVf_LOCKED)
111#define CvLOCKED_on(cv) (CvFLAGS(cv) |= CVf_LOCKED)
112#define CvLOCKED_off(cv) (CvFLAGS(cv) &= ~CVf_LOCKED)
1aff0e91 113
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114#define CvLVALUE(cv) (CvFLAGS(cv) & CVf_LVALUE)
115#define CvLVALUE_on(cv) (CvFLAGS(cv) |= CVf_LVALUE)
116#define CvLVALUE_off(cv) (CvFLAGS(cv) &= ~CVf_LVALUE)
117
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118#define CvEVAL(cv) (CvUNIQUE(cv) && !SvFAKE(cv))
119#define CvEVAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_off(cv))
120#define CvEVAL_off(cv) CvUNIQUE_off(cv)
121
3c10abe3 122/* BEGIN|CHECK|INIT|UNITCHECK|END */
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123#define CvSPECIAL(cv) (CvUNIQUE(cv) && SvFAKE(cv))
124#define CvSPECIAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_on(cv))
125#define CvSPECIAL_off(cv) (CvUNIQUE_off(cv),SvFAKE_off(cv))
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126
127#define CvCONST(cv) (CvFLAGS(cv) & CVf_CONST)
128#define CvCONST_on(cv) (CvFLAGS(cv) |= CVf_CONST)
129#define CvCONST_off(cv) (CvFLAGS(cv) &= ~CVf_CONST)
a4f1a029 130
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131#define CvWEAKOUTSIDE(cv) (CvFLAGS(cv) & CVf_WEAKOUTSIDE)
132#define CvWEAKOUTSIDE_on(cv) (CvFLAGS(cv) |= CVf_WEAKOUTSIDE)
133#define CvWEAKOUTSIDE_off(cv) (CvFLAGS(cv) &= ~CVf_WEAKOUTSIDE)
134
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135#define CvISXSUB(cv) (CvFLAGS(cv) & CVf_ISXSUB)
136#define CvISXSUB_on(cv) (CvFLAGS(cv) |= CVf_ISXSUB)
137#define CvISXSUB_off(cv) (CvFLAGS(cv) &= ~CVf_ISXSUB)
138
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139/* Flags for newXS_flags */
140#define XS_DYNAMIC_FILENAME 0x01 /* The filename isn't static */
141
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142/*
143=head1 CV reference counts and CvOUTSIDE
144
145=for apidoc m|bool|CvWEAKOUTSIDE|CV *cv
146
147Each CV has a pointer, C<CvOUTSIDE()>, to its lexically enclosing
148CV (if any). Because pointers to anonymous sub prototypes are
149stored in C<&> pad slots, it is a possible to get a circular reference,
150with the parent pointing to the child and vice-versa. To avoid the
151ensuing memory leak, we do not increment the reference count of the CV
152pointed to by C<CvOUTSIDE> in the I<one specific instance> that the parent
153has a C<&> pad slot pointing back to us. In this case, we set the
154C<CvWEAKOUTSIDE> flag in the child. This allows us to determine under what
155circumstances we should decrement the refcount of the parent when freeing
156the child.
157
eeb8d49e 158There is a further complication with non-closure anonymous subs (i.e. those
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159that do not refer to any lexicals outside that sub). In this case, the
160anonymous prototype is shared rather than being cloned. This has the
161consequence that the parent may be freed while there are still active
162children, eg
163
164 BEGIN { $a = sub { eval '$x' } }
165
166In this case, the BEGIN is freed immediately after execution since there
167are no active references to it: the anon sub prototype has
168C<CvWEAKOUTSIDE> set since it's not a closure, and $a points to the same
169CV, so it doesn't contribute to BEGIN's refcount either. When $a is
170executed, the C<eval '$x'> causes the chain of C<CvOUTSIDE>s to be followed,
171and the freed BEGIN is accessed.
172
173To avoid this, whenever a CV and its associated pad is freed, any
174C<&> entries in the pad are explicitly removed from the pad, and if the
175refcount of the pointed-to anon sub is still positive, then that
176child's C<CvOUTSIDE> is set to point to its grandparent. This will only
177occur in the single specific case of a non-closure anon prototype
178having one or more active references (such as C<$a> above).
179
180One other thing to consider is that a CV may be merely undefined
181rather than freed, eg C<undef &foo>. In this case, its refcount may
182not have reached zero, but we still delete its pad and its C<CvROOT> etc.
183Since various children may still have their C<CvOUTSIDE> pointing at this
184undefined CV, we keep its own C<CvOUTSIDE> for the time being, so that
185the chain of lexical scopes is unbroken. For example, the following
186should print 123:
187
188 my $x = 123;
189 sub tmp { sub { eval '$x' } }
190 my $a = tmp();
191 undef &tmp;
192 print $a->();
193
194=cut
195*/
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196
197/*
198 * Local variables:
199 * c-indentation-style: bsd
200 * c-basic-offset: 4
201 * indent-tabs-mode: t
202 * End:
203 *
204 * ex: set ts=8 sts=4 sw=4 noet:
205 */