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[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,
102d3b8a 4 * 2000, 2001, 2002, 2003, 2004, 2005, by Larry Wall and others
79072805
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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
fd40b977 11/* This structure must match XPVCV in B/C.pm and the beginning of XPVFM
57843af0 12 * in sv.h */
44a8e56a 13
79072805 14struct xpvcv {
311a25d9 15 NV xnv_nv; /* numeric value, if any */
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16 STRLEN xpv_cur; /* length of xp_pv as a C string */
17 STRLEN xpv_len; /* allocated size */
e4305a63 18 union {
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19 IV xivu_iv; /* integer value or pv offset */
20 UV xivu_uv;
21 void * xivu_p1;
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;
27 OP * xcv_start;
28 OP * xcv_root;
acfe0abc 29 void (*xcv_xsub) (pTHX_ CV*);
a0d0e21e 30 ANY xcv_xsubany;
8990e307 31 GV * xcv_gv;
57843af0 32 char * xcv_file;
b195d487 33 long xcv_depth; /* >= 2 indicates recursive call */
dd2155a4 34 PADLIST * xcv_padlist;
748a9306 35 CV * xcv_outside;
77a005ab 36 cv_flags_t xcv_flags;
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DM
37 U32 xcv_outside_seq; /* the COP sequence (at the point of our
38 * compilation) in the lexically enclosing
39 * sub */
79072805 40};
748a9306 41
954c1994 42/*
ccfc67b7
JH
43=head1 Handy Values
44
954c1994
GS
45=for apidoc AmU||Nullcv
46Null CV pointer.
47
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48=head1 CV Manipulation Functions
49
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50=for apidoc Am|HV*|CvSTASH|CV* cv
51Returns the stash of the CV.
52
53=cut
54*/
55
79072805 56#define Nullcv Null(CV*)
a5f75d66 57
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58#define CvSTASH(sv) ((XPVCV*)SvANY(sv))->xcv_stash
59#define CvSTART(sv) ((XPVCV*)SvANY(sv))->xcv_start
60#define CvROOT(sv) ((XPVCV*)SvANY(sv))->xcv_root
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61#define CvXSUB(sv) ((XPVCV*)SvANY(sv))->xcv_xsub
62#define CvXSUBANY(sv) ((XPVCV*)SvANY(sv))->xcv_xsubany
8990e307 63#define CvGV(sv) ((XPVCV*)SvANY(sv))->xcv_gv
57843af0 64#define CvFILE(sv) ((XPVCV*)SvANY(sv))->xcv_file
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65#ifdef USE_ITHREADS
66# define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = savepv(CopFILE(cop)))
67#else
68# define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = CopFILE(cop))
69#endif
9ec2a764 70#define CvFILEGV(sv) (gv_fetchfile(CvFILE(sv)))
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71#define CvDEPTH(sv) ((XPVCV*)SvANY(sv))->xcv_depth
72#define CvPADLIST(sv) ((XPVCV*)SvANY(sv))->xcv_padlist
748a9306 73#define CvOUTSIDE(sv) ((XPVCV*)SvANY(sv))->xcv_outside
a5f75d66 74#define CvFLAGS(sv) ((XPVCV*)SvANY(sv))->xcv_flags
a3985cdc 75#define CvOUTSIDE_SEQ(sv) ((XPVCV*)SvANY(sv))->xcv_outside_seq
a5f75d66 76
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77#define CVf_CLONE 0x0001 /* anon CV uses external lexicals */
78#define CVf_CLONED 0x0002 /* a clone of one of those */
79#define CVf_ANON 0x0004 /* CvGV() can't be trusted */
80#define CVf_OLDSTYLE 0x0008
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81#define CVf_UNIQUE 0x0010 /* sub is only called once (eg PL_main_cv,
82 * require, eval). Not to be confused
83 * with the GVf_UNIQUE flag associated
84 * with the :unique attribute */
77a005ab 85#define CVf_NODEBUG 0x0020 /* no DB::sub indirection for this CV
8ebc5c01 86 (esp. useful for special XSUBs) */
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87#define CVf_METHOD 0x0040 /* CV is explicitly marked as a method */
88#define CVf_LOCKED 0x0080 /* CV locks itself or first arg on entry */
cd06dffe 89#define CVf_LVALUE 0x0100 /* CV return value can be used as lvalue */
beab0874 90#define CVf_CONST 0x0200 /* inlinable sub */
7dafbf52 91#define CVf_WEAKOUTSIDE 0x0400 /* CvOUTSIDE isn't ref counted */
06492da6 92#define CVf_ASSERTION 0x0800 /* CV called only when asserting */
7dafbf52 93
d3cea301 94/* This symbol for optimised communication between toke.c and op.c: */
06492da6 95#define CVf_BUILTIN_ATTRS (CVf_METHOD|CVf_LOCKED|CVf_LVALUE|CVf_ASSERTION)
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96
97#define CvCLONE(cv) (CvFLAGS(cv) & CVf_CLONE)
98#define CvCLONE_on(cv) (CvFLAGS(cv) |= CVf_CLONE)
99#define CvCLONE_off(cv) (CvFLAGS(cv) &= ~CVf_CLONE)
100
101#define CvCLONED(cv) (CvFLAGS(cv) & CVf_CLONED)
102#define CvCLONED_on(cv) (CvFLAGS(cv) |= CVf_CLONED)
103#define CvCLONED_off(cv) (CvFLAGS(cv) &= ~CVf_CLONED)
104
105#define CvANON(cv) (CvFLAGS(cv) & CVf_ANON)
106#define CvANON_on(cv) (CvFLAGS(cv) |= CVf_ANON)
107#define CvANON_off(cv) (CvFLAGS(cv) &= ~CVf_ANON)
79072805 108
67caa1fe 109#ifdef PERL_XSUB_OLDSTYLE
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110#define CvOLDSTYLE(cv) (CvFLAGS(cv) & CVf_OLDSTYLE)
111#define CvOLDSTYLE_on(cv) (CvFLAGS(cv) |= CVf_OLDSTYLE)
112#define CvOLDSTYLE_off(cv) (CvFLAGS(cv) &= ~CVf_OLDSTYLE)
67caa1fe 113#endif
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114
115#define CvUNIQUE(cv) (CvFLAGS(cv) & CVf_UNIQUE)
116#define CvUNIQUE_on(cv) (CvFLAGS(cv) |= CVf_UNIQUE)
117#define CvUNIQUE_off(cv) (CvFLAGS(cv) &= ~CVf_UNIQUE)
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118
119#define CvNODEBUG(cv) (CvFLAGS(cv) & CVf_NODEBUG)
120#define CvNODEBUG_on(cv) (CvFLAGS(cv) |= CVf_NODEBUG)
121#define CvNODEBUG_off(cv) (CvFLAGS(cv) &= ~CVf_NODEBUG)
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122
123#define CvMETHOD(cv) (CvFLAGS(cv) & CVf_METHOD)
124#define CvMETHOD_on(cv) (CvFLAGS(cv) |= CVf_METHOD)
125#define CvMETHOD_off(cv) (CvFLAGS(cv) &= ~CVf_METHOD)
126
127#define CvLOCKED(cv) (CvFLAGS(cv) & CVf_LOCKED)
128#define CvLOCKED_on(cv) (CvFLAGS(cv) |= CVf_LOCKED)
129#define CvLOCKED_off(cv) (CvFLAGS(cv) &= ~CVf_LOCKED)
1aff0e91 130
cd06dffe
GS
131#define CvLVALUE(cv) (CvFLAGS(cv) & CVf_LVALUE)
132#define CvLVALUE_on(cv) (CvFLAGS(cv) |= CVf_LVALUE)
133#define CvLVALUE_off(cv) (CvFLAGS(cv) &= ~CVf_LVALUE)
134
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135#define CvASSERTION(cv) (CvFLAGS(cv) & CVf_ASSERTION)
136#define CvASSERTION_on(cv) (CvFLAGS(cv) |= CVf_ASSERTION)
137#define CvASSERTION_off(cv) (CvFLAGS(cv) &= ~CVf_ASSERTION)
138
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139#define CvEVAL(cv) (CvUNIQUE(cv) && !SvFAKE(cv))
140#define CvEVAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_off(cv))
141#define CvEVAL_off(cv) CvUNIQUE_off(cv)
142
bec31f9a 143/* BEGIN|CHECK|INIT|END */
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144#define CvSPECIAL(cv) (CvUNIQUE(cv) && SvFAKE(cv))
145#define CvSPECIAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_on(cv))
146#define CvSPECIAL_off(cv) (CvUNIQUE_off(cv),SvFAKE_off(cv))
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147
148#define CvCONST(cv) (CvFLAGS(cv) & CVf_CONST)
149#define CvCONST_on(cv) (CvFLAGS(cv) |= CVf_CONST)
150#define CvCONST_off(cv) (CvFLAGS(cv) &= ~CVf_CONST)
a4f1a029 151
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152#define CvWEAKOUTSIDE(cv) (CvFLAGS(cv) & CVf_WEAKOUTSIDE)
153#define CvWEAKOUTSIDE_on(cv) (CvFLAGS(cv) |= CVf_WEAKOUTSIDE)
154#define CvWEAKOUTSIDE_off(cv) (CvFLAGS(cv) &= ~CVf_WEAKOUTSIDE)
155
156
157/*
158=head1 CV reference counts and CvOUTSIDE
159
160=for apidoc m|bool|CvWEAKOUTSIDE|CV *cv
161
162Each CV has a pointer, C<CvOUTSIDE()>, to its lexically enclosing
163CV (if any). Because pointers to anonymous sub prototypes are
164stored in C<&> pad slots, it is a possible to get a circular reference,
165with the parent pointing to the child and vice-versa. To avoid the
166ensuing memory leak, we do not increment the reference count of the CV
167pointed to by C<CvOUTSIDE> in the I<one specific instance> that the parent
168has a C<&> pad slot pointing back to us. In this case, we set the
169C<CvWEAKOUTSIDE> flag in the child. This allows us to determine under what
170circumstances we should decrement the refcount of the parent when freeing
171the child.
172
173There is a further complication with non-closure anonymous subs (ie those
174that do not refer to any lexicals outside that sub). In this case, the
175anonymous prototype is shared rather than being cloned. This has the
176consequence that the parent may be freed while there are still active
177children, eg
178
179 BEGIN { $a = sub { eval '$x' } }
180
181In this case, the BEGIN is freed immediately after execution since there
182are no active references to it: the anon sub prototype has
183C<CvWEAKOUTSIDE> set since it's not a closure, and $a points to the same
184CV, so it doesn't contribute to BEGIN's refcount either. When $a is
185executed, the C<eval '$x'> causes the chain of C<CvOUTSIDE>s to be followed,
186and the freed BEGIN is accessed.
187
188To avoid this, whenever a CV and its associated pad is freed, any
189C<&> entries in the pad are explicitly removed from the pad, and if the
190refcount of the pointed-to anon sub is still positive, then that
191child's C<CvOUTSIDE> is set to point to its grandparent. This will only
192occur in the single specific case of a non-closure anon prototype
193having one or more active references (such as C<$a> above).
194
195One other thing to consider is that a CV may be merely undefined
196rather than freed, eg C<undef &foo>. In this case, its refcount may
197not have reached zero, but we still delete its pad and its C<CvROOT> etc.
198Since various children may still have their C<CvOUTSIDE> pointing at this
199undefined CV, we keep its own C<CvOUTSIDE> for the time being, so that
200the chain of lexical scopes is unbroken. For example, the following
201should print 123:
202
203 my $x = 123;
204 sub tmp { sub { eval '$x' } }
205 my $a = tmp();
206 undef &tmp;
207 print $a->();
208
209=cut
210*/
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NC
211
212/*
213 * Local variables:
214 * c-indentation-style: bsd
215 * c-basic-offset: 4
216 * indent-tabs-mode: t
217 * End:
218 *
219 * ex: set ts=8 sts=4 sw=4 noet:
220 */