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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 {
102d3b8a 15 IV awaiting_redevelopment; /* integer value */
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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 struct {
20 void *xnv_p1;
21 union {
22 void *xnv_p2;
23 IV xnv_i2;
24 } xnv_u2;
25 } xnv_s;
199f3245 26 NV xnvu_nv; /* numeric value, if any */
e4305a63 27 } xnv_u;
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28 MAGIC* xmg_magic; /* magic for scalar array */
29 HV* xmg_stash; /* class package */
30
31 HV * xcv_stash;
32 OP * xcv_start;
33 OP * xcv_root;
acfe0abc 34 void (*xcv_xsub) (pTHX_ CV*);
a0d0e21e 35 ANY xcv_xsubany;
8990e307 36 GV * xcv_gv;
57843af0 37 char * xcv_file;
b195d487 38 long xcv_depth; /* >= 2 indicates recursive call */
dd2155a4 39 PADLIST * xcv_padlist;
748a9306 40 CV * xcv_outside;
77a005ab 41 cv_flags_t xcv_flags;
a3985cdc
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42 U32 xcv_outside_seq; /* the COP sequence (at the point of our
43 * compilation) in the lexically enclosing
44 * sub */
79072805 45};
748a9306 46
954c1994 47/*
ccfc67b7
JH
48=head1 Handy Values
49
954c1994
GS
50=for apidoc AmU||Nullcv
51Null CV pointer.
52
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53=head1 CV Manipulation Functions
54
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55=for apidoc Am|HV*|CvSTASH|CV* cv
56Returns the stash of the CV.
57
58=cut
59*/
60
79072805 61#define Nullcv Null(CV*)
a5f75d66 62
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63#define CvSTASH(sv) ((XPVCV*)SvANY(sv))->xcv_stash
64#define CvSTART(sv) ((XPVCV*)SvANY(sv))->xcv_start
65#define CvROOT(sv) ((XPVCV*)SvANY(sv))->xcv_root
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66#define CvXSUB(sv) ((XPVCV*)SvANY(sv))->xcv_xsub
67#define CvXSUBANY(sv) ((XPVCV*)SvANY(sv))->xcv_xsubany
8990e307 68#define CvGV(sv) ((XPVCV*)SvANY(sv))->xcv_gv
57843af0 69#define CvFILE(sv) ((XPVCV*)SvANY(sv))->xcv_file
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70#ifdef USE_ITHREADS
71# define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = savepv(CopFILE(cop)))
72#else
73# define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = CopFILE(cop))
74#endif
9ec2a764 75#define CvFILEGV(sv) (gv_fetchfile(CvFILE(sv)))
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76#define CvDEPTH(sv) ((XPVCV*)SvANY(sv))->xcv_depth
77#define CvPADLIST(sv) ((XPVCV*)SvANY(sv))->xcv_padlist
748a9306 78#define CvOUTSIDE(sv) ((XPVCV*)SvANY(sv))->xcv_outside
a5f75d66 79#define CvFLAGS(sv) ((XPVCV*)SvANY(sv))->xcv_flags
a3985cdc 80#define CvOUTSIDE_SEQ(sv) ((XPVCV*)SvANY(sv))->xcv_outside_seq
a5f75d66 81
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82#define CVf_CLONE 0x0001 /* anon CV uses external lexicals */
83#define CVf_CLONED 0x0002 /* a clone of one of those */
84#define CVf_ANON 0x0004 /* CvGV() can't be trusted */
85#define CVf_OLDSTYLE 0x0008
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86#define CVf_UNIQUE 0x0010 /* sub is only called once (eg PL_main_cv,
87 * require, eval). Not to be confused
88 * with the GVf_UNIQUE flag associated
89 * with the :unique attribute */
77a005ab 90#define CVf_NODEBUG 0x0020 /* no DB::sub indirection for this CV
8ebc5c01 91 (esp. useful for special XSUBs) */
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92#define CVf_METHOD 0x0040 /* CV is explicitly marked as a method */
93#define CVf_LOCKED 0x0080 /* CV locks itself or first arg on entry */
cd06dffe 94#define CVf_LVALUE 0x0100 /* CV return value can be used as lvalue */
beab0874 95#define CVf_CONST 0x0200 /* inlinable sub */
7dafbf52 96#define CVf_WEAKOUTSIDE 0x0400 /* CvOUTSIDE isn't ref counted */
06492da6 97#define CVf_ASSERTION 0x0800 /* CV called only when asserting */
7dafbf52 98
d3cea301 99/* This symbol for optimised communication between toke.c and op.c: */
06492da6 100#define CVf_BUILTIN_ATTRS (CVf_METHOD|CVf_LOCKED|CVf_LVALUE|CVf_ASSERTION)
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101
102#define CvCLONE(cv) (CvFLAGS(cv) & CVf_CLONE)
103#define CvCLONE_on(cv) (CvFLAGS(cv) |= CVf_CLONE)
104#define CvCLONE_off(cv) (CvFLAGS(cv) &= ~CVf_CLONE)
105
106#define CvCLONED(cv) (CvFLAGS(cv) & CVf_CLONED)
107#define CvCLONED_on(cv) (CvFLAGS(cv) |= CVf_CLONED)
108#define CvCLONED_off(cv) (CvFLAGS(cv) &= ~CVf_CLONED)
109
110#define CvANON(cv) (CvFLAGS(cv) & CVf_ANON)
111#define CvANON_on(cv) (CvFLAGS(cv) |= CVf_ANON)
112#define CvANON_off(cv) (CvFLAGS(cv) &= ~CVf_ANON)
79072805 113
67caa1fe 114#ifdef PERL_XSUB_OLDSTYLE
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115#define CvOLDSTYLE(cv) (CvFLAGS(cv) & CVf_OLDSTYLE)
116#define CvOLDSTYLE_on(cv) (CvFLAGS(cv) |= CVf_OLDSTYLE)
117#define CvOLDSTYLE_off(cv) (CvFLAGS(cv) &= ~CVf_OLDSTYLE)
67caa1fe 118#endif
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119
120#define CvUNIQUE(cv) (CvFLAGS(cv) & CVf_UNIQUE)
121#define CvUNIQUE_on(cv) (CvFLAGS(cv) |= CVf_UNIQUE)
122#define CvUNIQUE_off(cv) (CvFLAGS(cv) &= ~CVf_UNIQUE)
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123
124#define CvNODEBUG(cv) (CvFLAGS(cv) & CVf_NODEBUG)
125#define CvNODEBUG_on(cv) (CvFLAGS(cv) |= CVf_NODEBUG)
126#define CvNODEBUG_off(cv) (CvFLAGS(cv) &= ~CVf_NODEBUG)
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127
128#define CvMETHOD(cv) (CvFLAGS(cv) & CVf_METHOD)
129#define CvMETHOD_on(cv) (CvFLAGS(cv) |= CVf_METHOD)
130#define CvMETHOD_off(cv) (CvFLAGS(cv) &= ~CVf_METHOD)
131
132#define CvLOCKED(cv) (CvFLAGS(cv) & CVf_LOCKED)
133#define CvLOCKED_on(cv) (CvFLAGS(cv) |= CVf_LOCKED)
134#define CvLOCKED_off(cv) (CvFLAGS(cv) &= ~CVf_LOCKED)
1aff0e91 135
cd06dffe
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136#define CvLVALUE(cv) (CvFLAGS(cv) & CVf_LVALUE)
137#define CvLVALUE_on(cv) (CvFLAGS(cv) |= CVf_LVALUE)
138#define CvLVALUE_off(cv) (CvFLAGS(cv) &= ~CVf_LVALUE)
139
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140#define CvASSERTION(cv) (CvFLAGS(cv) & CVf_ASSERTION)
141#define CvASSERTION_on(cv) (CvFLAGS(cv) |= CVf_ASSERTION)
142#define CvASSERTION_off(cv) (CvFLAGS(cv) &= ~CVf_ASSERTION)
143
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144#define CvEVAL(cv) (CvUNIQUE(cv) && !SvFAKE(cv))
145#define CvEVAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_off(cv))
146#define CvEVAL_off(cv) CvUNIQUE_off(cv)
147
bec31f9a 148/* BEGIN|CHECK|INIT|END */
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149#define CvSPECIAL(cv) (CvUNIQUE(cv) && SvFAKE(cv))
150#define CvSPECIAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_on(cv))
151#define CvSPECIAL_off(cv) (CvUNIQUE_off(cv),SvFAKE_off(cv))
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152
153#define CvCONST(cv) (CvFLAGS(cv) & CVf_CONST)
154#define CvCONST_on(cv) (CvFLAGS(cv) |= CVf_CONST)
155#define CvCONST_off(cv) (CvFLAGS(cv) &= ~CVf_CONST)
a4f1a029 156
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157#define CvWEAKOUTSIDE(cv) (CvFLAGS(cv) & CVf_WEAKOUTSIDE)
158#define CvWEAKOUTSIDE_on(cv) (CvFLAGS(cv) |= CVf_WEAKOUTSIDE)
159#define CvWEAKOUTSIDE_off(cv) (CvFLAGS(cv) &= ~CVf_WEAKOUTSIDE)
160
161
162/*
163=head1 CV reference counts and CvOUTSIDE
164
165=for apidoc m|bool|CvWEAKOUTSIDE|CV *cv
166
167Each CV has a pointer, C<CvOUTSIDE()>, to its lexically enclosing
168CV (if any). Because pointers to anonymous sub prototypes are
169stored in C<&> pad slots, it is a possible to get a circular reference,
170with the parent pointing to the child and vice-versa. To avoid the
171ensuing memory leak, we do not increment the reference count of the CV
172pointed to by C<CvOUTSIDE> in the I<one specific instance> that the parent
173has a C<&> pad slot pointing back to us. In this case, we set the
174C<CvWEAKOUTSIDE> flag in the child. This allows us to determine under what
175circumstances we should decrement the refcount of the parent when freeing
176the child.
177
178There is a further complication with non-closure anonymous subs (ie those
179that do not refer to any lexicals outside that sub). In this case, the
180anonymous prototype is shared rather than being cloned. This has the
181consequence that the parent may be freed while there are still active
182children, eg
183
184 BEGIN { $a = sub { eval '$x' } }
185
186In this case, the BEGIN is freed immediately after execution since there
187are no active references to it: the anon sub prototype has
188C<CvWEAKOUTSIDE> set since it's not a closure, and $a points to the same
189CV, so it doesn't contribute to BEGIN's refcount either. When $a is
190executed, the C<eval '$x'> causes the chain of C<CvOUTSIDE>s to be followed,
191and the freed BEGIN is accessed.
192
193To avoid this, whenever a CV and its associated pad is freed, any
194C<&> entries in the pad are explicitly removed from the pad, and if the
195refcount of the pointed-to anon sub is still positive, then that
196child's C<CvOUTSIDE> is set to point to its grandparent. This will only
197occur in the single specific case of a non-closure anon prototype
198having one or more active references (such as C<$a> above).
199
200One other thing to consider is that a CV may be merely undefined
201rather than freed, eg C<undef &foo>. In this case, its refcount may
202not have reached zero, but we still delete its pad and its C<CvROOT> etc.
203Since various children may still have their C<CvOUTSIDE> pointing at this
204undefined CV, we keep its own C<CvOUTSIDE> for the time being, so that
205the chain of lexical scopes is unbroken. For example, the following
206should print 123:
207
208 my $x = 123;
209 sub tmp { sub { eval '$x' } }
210 my $a = tmp();
211 undef &tmp;
212 print $a->();
213
214=cut
215*/
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NC
216
217/*
218 * Local variables:
219 * c-indentation-style: bsd
220 * c-basic-offset: 4
221 * indent-tabs-mode: t
222 * End:
223 *
224 * ex: set ts=8 sts=4 sw=4 noet:
225 */