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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 {
bb172083 18 IV xivu_iv;
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19 UV xivu_uv;
20 void * xivu_p1;
bb172083 21 I32 xivu_i32; /* depth, >= 2 indicates recursive call */
311a25d9 22 } xiv_u;
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23 MAGIC* xmg_magic; /* magic for scalar array */
24 HV* xmg_stash; /* class package */
25
26 HV * xcv_stash;
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27 union {
28 OP * xcv_start;
29 ANY xcv_xsubany;
30 } xcv_start_u;
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31 union {
32 OP * xcv_root;
33 void (*xcv_xsub) (pTHX_ CV*);
34 } xcv_root_u;
8990e307 35 GV * xcv_gv;
57843af0 36 char * xcv_file;
bb172083 37 long xcv_depth;
dd2155a4 38 PADLIST * xcv_padlist;
748a9306 39 CV * xcv_outside;
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40 U32 xcv_outside_seq; /* the COP sequence (at the point of our
41 * compilation) in the lexically enclosing
42 * sub */
bb172083 43 cv_flags_t xcv_flags;
79072805 44};
748a9306 45
954c1994 46/*
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47=head1 Handy Values
48
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49=for apidoc AmU||Nullcv
50Null CV pointer.
51
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52=head1 CV Manipulation Functions
53
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54=for apidoc Am|HV*|CvSTASH|CV* cv
55Returns the stash of the CV.
56
57=cut
58*/
59
79072805 60#define Nullcv Null(CV*)
a5f75d66 61
79072805 62#define CvSTASH(sv) ((XPVCV*)SvANY(sv))->xcv_stash
bf53b3a5 63#define CvSTART(sv) ((XPVCV*)SvANY(sv))->xcv_start_u.xcv_start
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64#define CvROOT(sv) ((XPVCV*)SvANY(sv))->xcv_root_u.xcv_root
65#define CvXSUB(sv) ((XPVCV*)SvANY(sv))->xcv_root_u.xcv_xsub
bf53b3a5 66#define CvXSUBANY(sv) ((XPVCV*)SvANY(sv))->xcv_start_u.xcv_xsubany
8990e307 67#define CvGV(sv) ((XPVCV*)SvANY(sv))->xcv_gv
57843af0 68#define CvFILE(sv) ((XPVCV*)SvANY(sv))->xcv_file
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69#ifdef USE_ITHREADS
70# define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = savepv(CopFILE(cop)))
71#else
72# define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = CopFILE(cop))
73#endif
9ec2a764 74#define CvFILEGV(sv) (gv_fetchfile(CvFILE(sv)))
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75#if defined(__GNUC__) && !defined(PERL_GCC_BRACE_GROUPS_FORBIDDEN)
76# define CvDEPTH(sv) (*({const CV *_cv = (CV *)sv; \
77 assert(SvTYPE(_cv) == SVt_PVCV); \
78 &((XPVCV*)SvANY(_cv))->xiv_u.xivu_i32; \
79 }))
80#else
81# define CvDEPTH(sv) ((XPVCV*)SvANY(sv))->xiv_u.xivu_i32
82#endif
79072805 83#define CvPADLIST(sv) ((XPVCV*)SvANY(sv))->xcv_padlist
748a9306 84#define CvOUTSIDE(sv) ((XPVCV*)SvANY(sv))->xcv_outside
a5f75d66 85#define CvFLAGS(sv) ((XPVCV*)SvANY(sv))->xcv_flags
a3985cdc 86#define CvOUTSIDE_SEQ(sv) ((XPVCV*)SvANY(sv))->xcv_outside_seq
a5f75d66 87
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88#define CVf_METHOD 0x0001 /* CV is explicitly marked as a method */
89#define CVf_LOCKED 0x0002 /* CV locks itself or first arg on entry */
90#define CVf_LVALUE 0x0004 /* CV return value can be used as lvalue */
91#define CVf_ASSERTION 0x0008 /* CV called only when asserting */
92
93#define CVf_WEAKOUTSIDE 0x0010 /* CvOUTSIDE isn't ref counted */
94#define CVf_CLONE 0x0020 /* anon CV uses external lexicals */
95#define CVf_CLONED 0x0040 /* a clone of one of those */
96#define CVf_ANON 0x0080 /* CvGV() can't be trusted */
97#define CVf_UNIQUE 0x0100 /* sub is only called once (eg PL_main_cv,
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98 * require, eval). Not to be confused
99 * with the GVf_UNIQUE flag associated
100 * with the :unique attribute */
5b4563c8 101#define CVf_NODEBUG 0x0200 /* no DB::sub indirection for this CV
8ebc5c01 102 (esp. useful for special XSUBs) */
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103#define CVf_CONST 0x0400 /* inlinable sub */
104#define CVf_OLDSTYLE 0x0800
d04ba589 105#define CVf_ISXSUB 0x1000 /* CV is an XSUB, not pure perl. */
7dafbf52 106
d3cea301 107/* This symbol for optimised communication between toke.c and op.c: */
06492da6 108#define CVf_BUILTIN_ATTRS (CVf_METHOD|CVf_LOCKED|CVf_LVALUE|CVf_ASSERTION)
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109
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)
113
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)
117
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)
79072805 121
67caa1fe 122#ifdef PERL_XSUB_OLDSTYLE
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123#define CvOLDSTYLE(cv) (CvFLAGS(cv) & CVf_OLDSTYLE)
124#define CvOLDSTYLE_on(cv) (CvFLAGS(cv) |= CVf_OLDSTYLE)
125#define CvOLDSTYLE_off(cv) (CvFLAGS(cv) &= ~CVf_OLDSTYLE)
67caa1fe 126#endif
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127
128#define CvUNIQUE(cv) (CvFLAGS(cv) & CVf_UNIQUE)
129#define CvUNIQUE_on(cv) (CvFLAGS(cv) |= CVf_UNIQUE)
130#define CvUNIQUE_off(cv) (CvFLAGS(cv) &= ~CVf_UNIQUE)
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131
132#define CvNODEBUG(cv) (CvFLAGS(cv) & CVf_NODEBUG)
133#define CvNODEBUG_on(cv) (CvFLAGS(cv) |= CVf_NODEBUG)
134#define CvNODEBUG_off(cv) (CvFLAGS(cv) &= ~CVf_NODEBUG)
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135
136#define CvMETHOD(cv) (CvFLAGS(cv) & CVf_METHOD)
137#define CvMETHOD_on(cv) (CvFLAGS(cv) |= CVf_METHOD)
138#define CvMETHOD_off(cv) (CvFLAGS(cv) &= ~CVf_METHOD)
139
140#define CvLOCKED(cv) (CvFLAGS(cv) & CVf_LOCKED)
141#define CvLOCKED_on(cv) (CvFLAGS(cv) |= CVf_LOCKED)
142#define CvLOCKED_off(cv) (CvFLAGS(cv) &= ~CVf_LOCKED)
1aff0e91 143
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144#define CvLVALUE(cv) (CvFLAGS(cv) & CVf_LVALUE)
145#define CvLVALUE_on(cv) (CvFLAGS(cv) |= CVf_LVALUE)
146#define CvLVALUE_off(cv) (CvFLAGS(cv) &= ~CVf_LVALUE)
147
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148#define CvASSERTION(cv) (CvFLAGS(cv) & CVf_ASSERTION)
149#define CvASSERTION_on(cv) (CvFLAGS(cv) |= CVf_ASSERTION)
150#define CvASSERTION_off(cv) (CvFLAGS(cv) &= ~CVf_ASSERTION)
151
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152#define CvEVAL(cv) (CvUNIQUE(cv) && !SvFAKE(cv))
153#define CvEVAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_off(cv))
154#define CvEVAL_off(cv) CvUNIQUE_off(cv)
155
bec31f9a 156/* BEGIN|CHECK|INIT|END */
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157#define CvSPECIAL(cv) (CvUNIQUE(cv) && SvFAKE(cv))
158#define CvSPECIAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_on(cv))
159#define CvSPECIAL_off(cv) (CvUNIQUE_off(cv),SvFAKE_off(cv))
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160
161#define CvCONST(cv) (CvFLAGS(cv) & CVf_CONST)
162#define CvCONST_on(cv) (CvFLAGS(cv) |= CVf_CONST)
163#define CvCONST_off(cv) (CvFLAGS(cv) &= ~CVf_CONST)
a4f1a029 164
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165#define CvWEAKOUTSIDE(cv) (CvFLAGS(cv) & CVf_WEAKOUTSIDE)
166#define CvWEAKOUTSIDE_on(cv) (CvFLAGS(cv) |= CVf_WEAKOUTSIDE)
167#define CvWEAKOUTSIDE_off(cv) (CvFLAGS(cv) &= ~CVf_WEAKOUTSIDE)
168
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169#define CvISXSUB(cv) (CvFLAGS(cv) & CVf_ISXSUB)
170#define CvISXSUB_on(cv) (CvFLAGS(cv) |= CVf_ISXSUB)
171#define CvISXSUB_off(cv) (CvFLAGS(cv) &= ~CVf_ISXSUB)
172
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173/*
174=head1 CV reference counts and CvOUTSIDE
175
176=for apidoc m|bool|CvWEAKOUTSIDE|CV *cv
177
178Each CV has a pointer, C<CvOUTSIDE()>, to its lexically enclosing
179CV (if any). Because pointers to anonymous sub prototypes are
180stored in C<&> pad slots, it is a possible to get a circular reference,
181with the parent pointing to the child and vice-versa. To avoid the
182ensuing memory leak, we do not increment the reference count of the CV
183pointed to by C<CvOUTSIDE> in the I<one specific instance> that the parent
184has a C<&> pad slot pointing back to us. In this case, we set the
185C<CvWEAKOUTSIDE> flag in the child. This allows us to determine under what
186circumstances we should decrement the refcount of the parent when freeing
187the child.
188
eeb8d49e 189There is a further complication with non-closure anonymous subs (i.e. those
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190that do not refer to any lexicals outside that sub). In this case, the
191anonymous prototype is shared rather than being cloned. This has the
192consequence that the parent may be freed while there are still active
193children, eg
194
195 BEGIN { $a = sub { eval '$x' } }
196
197In this case, the BEGIN is freed immediately after execution since there
198are no active references to it: the anon sub prototype has
199C<CvWEAKOUTSIDE> set since it's not a closure, and $a points to the same
200CV, so it doesn't contribute to BEGIN's refcount either. When $a is
201executed, the C<eval '$x'> causes the chain of C<CvOUTSIDE>s to be followed,
202and the freed BEGIN is accessed.
203
204To avoid this, whenever a CV and its associated pad is freed, any
205C<&> entries in the pad are explicitly removed from the pad, and if the
206refcount of the pointed-to anon sub is still positive, then that
207child's C<CvOUTSIDE> is set to point to its grandparent. This will only
208occur in the single specific case of a non-closure anon prototype
209having one or more active references (such as C<$a> above).
210
211One other thing to consider is that a CV may be merely undefined
212rather than freed, eg C<undef &foo>. In this case, its refcount may
213not have reached zero, but we still delete its pad and its C<CvROOT> etc.
214Since various children may still have their C<CvOUTSIDE> pointing at this
215undefined CV, we keep its own C<CvOUTSIDE> for the time being, so that
216the chain of lexical scopes is unbroken. For example, the following
217should print 123:
218
219 my $x = 123;
220 sub tmp { sub { eval '$x' } }
221 my $a = tmp();
222 undef &tmp;
223 print $a->();
224
225=cut
226*/
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227
228/*
229 * Local variables:
230 * c-indentation-style: bsd
231 * c-basic-offset: 4
232 * indent-tabs-mode: t
233 * End:
234 *
235 * ex: set ts=8 sts=4 sw=4 noet:
236 */