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xcv_start and xcv_xsubany can be merged into a union, as they are never
[perl5.git] / cv.h
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a0d0e21e 1/* cv.h
79072805 2 *
4bb101f2 3 * Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1999,
bf53b3a5 4 * 2000, 2001, 2002, 2003, 2004, 2005, 2006, 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 {
311a25d9 14 NV xnv_nv; /* numeric value, if any */
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15 STRLEN xpv_cur; /* length of xp_pv as a C string */
16 STRLEN xpv_len; /* allocated size */
e4305a63 17 union {
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18 IV xivu_iv; /* integer value or pv offset */
19 UV xivu_uv;
20 void * xivu_p1;
21 } xiv_u;
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22 MAGIC* xmg_magic; /* magic for scalar array */
23 HV* xmg_stash; /* class package */
24
25 HV * xcv_stash;
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26 union {
27 OP * xcv_start;
28 ANY xcv_xsubany;
29 } xcv_start_u;
79072805 30 OP * xcv_root;
acfe0abc 31 void (*xcv_xsub) (pTHX_ CV*);
8990e307 32 GV * xcv_gv;
57843af0 33 char * xcv_file;
b195d487 34 long xcv_depth; /* >= 2 indicates recursive call */
dd2155a4 35 PADLIST * xcv_padlist;
748a9306 36 CV * xcv_outside;
77a005ab 37 cv_flags_t xcv_flags;
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38 U32 xcv_outside_seq; /* the COP sequence (at the point of our
39 * compilation) in the lexically enclosing
40 * sub */
79072805 41};
748a9306 42
954c1994 43/*
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44=head1 Handy Values
45
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46=for apidoc AmU||Nullcv
47Null CV pointer.
48
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49=head1 CV Manipulation Functions
50
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51=for apidoc Am|HV*|CvSTASH|CV* cv
52Returns the stash of the CV.
53
54=cut
55*/
56
79072805 57#define Nullcv Null(CV*)
a5f75d66 58
79072805 59#define CvSTASH(sv) ((XPVCV*)SvANY(sv))->xcv_stash
bf53b3a5 60#define CvSTART(sv) ((XPVCV*)SvANY(sv))->xcv_start_u.xcv_start
79072805 61#define CvROOT(sv) ((XPVCV*)SvANY(sv))->xcv_root
a0d0e21e 62#define CvXSUB(sv) ((XPVCV*)SvANY(sv))->xcv_xsub
bf53b3a5 63#define CvXSUBANY(sv) ((XPVCV*)SvANY(sv))->xcv_start_u.xcv_xsubany
8990e307 64#define CvGV(sv) ((XPVCV*)SvANY(sv))->xcv_gv
57843af0 65#define CvFILE(sv) ((XPVCV*)SvANY(sv))->xcv_file
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66#ifdef USE_ITHREADS
67# define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = savepv(CopFILE(cop)))
68#else
69# define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = CopFILE(cop))
70#endif
9ec2a764 71#define CvFILEGV(sv) (gv_fetchfile(CvFILE(sv)))
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72#define CvDEPTH(sv) ((XPVCV*)SvANY(sv))->xcv_depth
73#define CvPADLIST(sv) ((XPVCV*)SvANY(sv))->xcv_padlist
748a9306 74#define CvOUTSIDE(sv) ((XPVCV*)SvANY(sv))->xcv_outside
a5f75d66 75#define CvFLAGS(sv) ((XPVCV*)SvANY(sv))->xcv_flags
a3985cdc 76#define CvOUTSIDE_SEQ(sv) ((XPVCV*)SvANY(sv))->xcv_outside_seq
a5f75d66 77
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78#define CVf_METHOD 0x0001 /* CV is explicitly marked as a method */
79#define CVf_LOCKED 0x0002 /* CV locks itself or first arg on entry */
80#define CVf_LVALUE 0x0004 /* CV return value can be used as lvalue */
81#define CVf_ASSERTION 0x0008 /* CV called only when asserting */
82
83#define CVf_WEAKOUTSIDE 0x0010 /* CvOUTSIDE isn't ref counted */
84#define CVf_CLONE 0x0020 /* anon CV uses external lexicals */
85#define CVf_CLONED 0x0040 /* a clone of one of those */
86#define CVf_ANON 0x0080 /* CvGV() can't be trusted */
87#define CVf_UNIQUE 0x0100 /* sub is only called once (eg PL_main_cv,
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88 * require, eval). Not to be confused
89 * with the GVf_UNIQUE flag associated
90 * with the :unique attribute */
5b4563c8 91#define CVf_NODEBUG 0x0200 /* no DB::sub indirection for this CV
8ebc5c01 92 (esp. useful for special XSUBs) */
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93#define CVf_CONST 0x0400 /* inlinable sub */
94#define CVf_OLDSTYLE 0x0800
7dafbf52 95
d3cea301 96/* This symbol for optimised communication between toke.c and op.c: */
06492da6 97#define CVf_BUILTIN_ATTRS (CVf_METHOD|CVf_LOCKED|CVf_LVALUE|CVf_ASSERTION)
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98
99#define CvCLONE(cv) (CvFLAGS(cv) & CVf_CLONE)
100#define CvCLONE_on(cv) (CvFLAGS(cv) |= CVf_CLONE)
101#define CvCLONE_off(cv) (CvFLAGS(cv) &= ~CVf_CLONE)
102
103#define CvCLONED(cv) (CvFLAGS(cv) & CVf_CLONED)
104#define CvCLONED_on(cv) (CvFLAGS(cv) |= CVf_CLONED)
105#define CvCLONED_off(cv) (CvFLAGS(cv) &= ~CVf_CLONED)
106
107#define CvANON(cv) (CvFLAGS(cv) & CVf_ANON)
108#define CvANON_on(cv) (CvFLAGS(cv) |= CVf_ANON)
109#define CvANON_off(cv) (CvFLAGS(cv) &= ~CVf_ANON)
79072805 110
67caa1fe 111#ifdef PERL_XSUB_OLDSTYLE
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112#define CvOLDSTYLE(cv) (CvFLAGS(cv) & CVf_OLDSTYLE)
113#define CvOLDSTYLE_on(cv) (CvFLAGS(cv) |= CVf_OLDSTYLE)
114#define CvOLDSTYLE_off(cv) (CvFLAGS(cv) &= ~CVf_OLDSTYLE)
67caa1fe 115#endif
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116
117#define CvUNIQUE(cv) (CvFLAGS(cv) & CVf_UNIQUE)
118#define CvUNIQUE_on(cv) (CvFLAGS(cv) |= CVf_UNIQUE)
119#define CvUNIQUE_off(cv) (CvFLAGS(cv) &= ~CVf_UNIQUE)
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120
121#define CvNODEBUG(cv) (CvFLAGS(cv) & CVf_NODEBUG)
122#define CvNODEBUG_on(cv) (CvFLAGS(cv) |= CVf_NODEBUG)
123#define CvNODEBUG_off(cv) (CvFLAGS(cv) &= ~CVf_NODEBUG)
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124
125#define CvMETHOD(cv) (CvFLAGS(cv) & CVf_METHOD)
126#define CvMETHOD_on(cv) (CvFLAGS(cv) |= CVf_METHOD)
127#define CvMETHOD_off(cv) (CvFLAGS(cv) &= ~CVf_METHOD)
128
129#define CvLOCKED(cv) (CvFLAGS(cv) & CVf_LOCKED)
130#define CvLOCKED_on(cv) (CvFLAGS(cv) |= CVf_LOCKED)
131#define CvLOCKED_off(cv) (CvFLAGS(cv) &= ~CVf_LOCKED)
1aff0e91 132
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133#define CvLVALUE(cv) (CvFLAGS(cv) & CVf_LVALUE)
134#define CvLVALUE_on(cv) (CvFLAGS(cv) |= CVf_LVALUE)
135#define CvLVALUE_off(cv) (CvFLAGS(cv) &= ~CVf_LVALUE)
136
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137#define CvASSERTION(cv) (CvFLAGS(cv) & CVf_ASSERTION)
138#define CvASSERTION_on(cv) (CvFLAGS(cv) |= CVf_ASSERTION)
139#define CvASSERTION_off(cv) (CvFLAGS(cv) &= ~CVf_ASSERTION)
140
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141#define CvEVAL(cv) (CvUNIQUE(cv) && !SvFAKE(cv))
142#define CvEVAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_off(cv))
143#define CvEVAL_off(cv) CvUNIQUE_off(cv)
144
bec31f9a 145/* BEGIN|CHECK|INIT|END */
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146#define CvSPECIAL(cv) (CvUNIQUE(cv) && SvFAKE(cv))
147#define CvSPECIAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_on(cv))
148#define CvSPECIAL_off(cv) (CvUNIQUE_off(cv),SvFAKE_off(cv))
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149
150#define CvCONST(cv) (CvFLAGS(cv) & CVf_CONST)
151#define CvCONST_on(cv) (CvFLAGS(cv) |= CVf_CONST)
152#define CvCONST_off(cv) (CvFLAGS(cv) &= ~CVf_CONST)
a4f1a029 153
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154#define CvWEAKOUTSIDE(cv) (CvFLAGS(cv) & CVf_WEAKOUTSIDE)
155#define CvWEAKOUTSIDE_on(cv) (CvFLAGS(cv) |= CVf_WEAKOUTSIDE)
156#define CvWEAKOUTSIDE_off(cv) (CvFLAGS(cv) &= ~CVf_WEAKOUTSIDE)
157
aed2304a 158#define CvISXSUB(cv) (CvXSUB(cv) ? TRUE : FALSE)
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159/*
160=head1 CV reference counts and CvOUTSIDE
161
162=for apidoc m|bool|CvWEAKOUTSIDE|CV *cv
163
164Each CV has a pointer, C<CvOUTSIDE()>, to its lexically enclosing
165CV (if any). Because pointers to anonymous sub prototypes are
166stored in C<&> pad slots, it is a possible to get a circular reference,
167with the parent pointing to the child and vice-versa. To avoid the
168ensuing memory leak, we do not increment the reference count of the CV
169pointed to by C<CvOUTSIDE> in the I<one specific instance> that the parent
170has a C<&> pad slot pointing back to us. In this case, we set the
171C<CvWEAKOUTSIDE> flag in the child. This allows us to determine under what
172circumstances we should decrement the refcount of the parent when freeing
173the child.
174
eeb8d49e 175There is a further complication with non-closure anonymous subs (i.e. those
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176that do not refer to any lexicals outside that sub). In this case, the
177anonymous prototype is shared rather than being cloned. This has the
178consequence that the parent may be freed while there are still active
179children, eg
180
181 BEGIN { $a = sub { eval '$x' } }
182
183In this case, the BEGIN is freed immediately after execution since there
184are no active references to it: the anon sub prototype has
185C<CvWEAKOUTSIDE> set since it's not a closure, and $a points to the same
186CV, so it doesn't contribute to BEGIN's refcount either. When $a is
187executed, the C<eval '$x'> causes the chain of C<CvOUTSIDE>s to be followed,
188and the freed BEGIN is accessed.
189
190To avoid this, whenever a CV and its associated pad is freed, any
191C<&> entries in the pad are explicitly removed from the pad, and if the
192refcount of the pointed-to anon sub is still positive, then that
193child's C<CvOUTSIDE> is set to point to its grandparent. This will only
194occur in the single specific case of a non-closure anon prototype
195having one or more active references (such as C<$a> above).
196
197One other thing to consider is that a CV may be merely undefined
198rather than freed, eg C<undef &foo>. In this case, its refcount may
199not have reached zero, but we still delete its pad and its C<CvROOT> etc.
200Since various children may still have their C<CvOUTSIDE> pointing at this
201undefined CV, we keep its own C<CvOUTSIDE> for the time being, so that
202the chain of lexical scopes is unbroken. For example, the following
203should print 123:
204
205 my $x = 123;
206 sub tmp { sub { eval '$x' } }
207 my $a = tmp();
208 undef &tmp;
209 print $a->();
210
211=cut
212*/
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213
214/*
215 * Local variables:
216 * c-indentation-style: bsd
217 * c-basic-offset: 4
218 * indent-tabs-mode: t
219 * End:
220 *
221 * ex: set ts=8 sts=4 sw=4 noet:
222 */