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a0d0e21e 1/* cv.h
79072805 2 *
4c79ee7a 3 * Copyright (c) 1991-2003, Larry Wall
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4 *
5 * You may distribute under the terms of either the GNU General Public
6 * License or the Artistic License, as specified in the README file.
7 *
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8 */
9
fd40b977 10/* This structure must match XPVCV in B/C.pm and the beginning of XPVFM
57843af0 11 * in sv.h */
44a8e56a 12
79072805 13struct xpvcv {
b84cd2cb 14 char * xpv_pv; /* pointer to malloced string (for prototype) */
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15 STRLEN xpv_cur; /* length of xp_pv as a C string */
16 STRLEN xpv_len; /* allocated size */
a0d0e21e 17 IV xof_off; /* integer value */
65202027 18 NV xnv_nv; /* numeric value, if any */
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19 MAGIC* xmg_magic; /* magic for scalar array */
20 HV* xmg_stash; /* class package */
21
22 HV * xcv_stash;
23 OP * xcv_start;
24 OP * xcv_root;
acfe0abc 25 void (*xcv_xsub) (pTHX_ CV*);
a0d0e21e 26 ANY xcv_xsubany;
8990e307 27 GV * xcv_gv;
57843af0 28 char * xcv_file;
b195d487 29 long xcv_depth; /* >= 2 indicates recursive call */
dd2155a4 30 PADLIST * xcv_padlist;
748a9306 31 CV * xcv_outside;
77a005ab 32 cv_flags_t xcv_flags;
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33 U32 xcv_outside_seq; /* the COP sequence (at the point of our
34 * compilation) in the lexically enclosing
35 * sub */
79072805 36};
748a9306 37
954c1994 38/*
ccfc67b7
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39=head1 Handy Values
40
954c1994
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41=for apidoc AmU||Nullcv
42Null CV pointer.
43
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44=head1 CV Manipulation Functions
45
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46=for apidoc Am|HV*|CvSTASH|CV* cv
47Returns the stash of the CV.
48
49=cut
50*/
51
79072805 52#define Nullcv Null(CV*)
a5f75d66 53
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54#define CvSTASH(sv) ((XPVCV*)SvANY(sv))->xcv_stash
55#define CvSTART(sv) ((XPVCV*)SvANY(sv))->xcv_start
56#define CvROOT(sv) ((XPVCV*)SvANY(sv))->xcv_root
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57#define CvXSUB(sv) ((XPVCV*)SvANY(sv))->xcv_xsub
58#define CvXSUBANY(sv) ((XPVCV*)SvANY(sv))->xcv_xsubany
8990e307 59#define CvGV(sv) ((XPVCV*)SvANY(sv))->xcv_gv
57843af0 60#define CvFILE(sv) ((XPVCV*)SvANY(sv))->xcv_file
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61#ifdef USE_ITHREADS
62# define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = savepv(CopFILE(cop)))
63#else
64# define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = CopFILE(cop))
65#endif
9ec2a764 66#define CvFILEGV(sv) (gv_fetchfile(CvFILE(sv)))
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67#define CvDEPTH(sv) ((XPVCV*)SvANY(sv))->xcv_depth
68#define CvPADLIST(sv) ((XPVCV*)SvANY(sv))->xcv_padlist
748a9306 69#define CvOUTSIDE(sv) ((XPVCV*)SvANY(sv))->xcv_outside
a5f75d66 70#define CvFLAGS(sv) ((XPVCV*)SvANY(sv))->xcv_flags
a3985cdc 71#define CvOUTSIDE_SEQ(sv) ((XPVCV*)SvANY(sv))->xcv_outside_seq
a5f75d66 72
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73#define CVf_CLONE 0x0001 /* anon CV uses external lexicals */
74#define CVf_CLONED 0x0002 /* a clone of one of those */
75#define CVf_ANON 0x0004 /* CvGV() can't be trusted */
76#define CVf_OLDSTYLE 0x0008
77#define CVf_UNIQUE 0x0010 /* can't be cloned */
78#define CVf_NODEBUG 0x0020 /* no DB::sub indirection for this CV
8ebc5c01 79 (esp. useful for special XSUBs) */
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80#define CVf_METHOD 0x0040 /* CV is explicitly marked as a method */
81#define CVf_LOCKED 0x0080 /* CV locks itself or first arg on entry */
cd06dffe 82#define CVf_LVALUE 0x0100 /* CV return value can be used as lvalue */
beab0874 83#define CVf_CONST 0x0200 /* inlinable sub */
7dafbf52 84#define CVf_WEAKOUTSIDE 0x0400 /* CvOUTSIDE isn't ref counted */
06492da6 85#define CVf_ASSERTION 0x0800 /* CV called only when asserting */
7dafbf52 86
d3cea301 87/* This symbol for optimised communication between toke.c and op.c: */
06492da6 88#define CVf_BUILTIN_ATTRS (CVf_METHOD|CVf_LOCKED|CVf_LVALUE|CVf_ASSERTION)
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89
90#define CvCLONE(cv) (CvFLAGS(cv) & CVf_CLONE)
91#define CvCLONE_on(cv) (CvFLAGS(cv) |= CVf_CLONE)
92#define CvCLONE_off(cv) (CvFLAGS(cv) &= ~CVf_CLONE)
93
94#define CvCLONED(cv) (CvFLAGS(cv) & CVf_CLONED)
95#define CvCLONED_on(cv) (CvFLAGS(cv) |= CVf_CLONED)
96#define CvCLONED_off(cv) (CvFLAGS(cv) &= ~CVf_CLONED)
97
98#define CvANON(cv) (CvFLAGS(cv) & CVf_ANON)
99#define CvANON_on(cv) (CvFLAGS(cv) |= CVf_ANON)
100#define CvANON_off(cv) (CvFLAGS(cv) &= ~CVf_ANON)
79072805 101
67caa1fe 102#ifdef PERL_XSUB_OLDSTYLE
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103#define CvOLDSTYLE(cv) (CvFLAGS(cv) & CVf_OLDSTYLE)
104#define CvOLDSTYLE_on(cv) (CvFLAGS(cv) |= CVf_OLDSTYLE)
105#define CvOLDSTYLE_off(cv) (CvFLAGS(cv) &= ~CVf_OLDSTYLE)
67caa1fe 106#endif
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107
108#define CvUNIQUE(cv) (CvFLAGS(cv) & CVf_UNIQUE)
109#define CvUNIQUE_on(cv) (CvFLAGS(cv) |= CVf_UNIQUE)
110#define CvUNIQUE_off(cv) (CvFLAGS(cv) &= ~CVf_UNIQUE)
8ebc5c01 111
112#define CvNODEBUG(cv) (CvFLAGS(cv) & CVf_NODEBUG)
113#define CvNODEBUG_on(cv) (CvFLAGS(cv) |= CVf_NODEBUG)
114#define CvNODEBUG_off(cv) (CvFLAGS(cv) &= ~CVf_NODEBUG)
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115
116#define CvMETHOD(cv) (CvFLAGS(cv) & CVf_METHOD)
117#define CvMETHOD_on(cv) (CvFLAGS(cv) |= CVf_METHOD)
118#define CvMETHOD_off(cv) (CvFLAGS(cv) &= ~CVf_METHOD)
119
120#define CvLOCKED(cv) (CvFLAGS(cv) & CVf_LOCKED)
121#define CvLOCKED_on(cv) (CvFLAGS(cv) |= CVf_LOCKED)
122#define CvLOCKED_off(cv) (CvFLAGS(cv) &= ~CVf_LOCKED)
1aff0e91 123
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124#define CvLVALUE(cv) (CvFLAGS(cv) & CVf_LVALUE)
125#define CvLVALUE_on(cv) (CvFLAGS(cv) |= CVf_LVALUE)
126#define CvLVALUE_off(cv) (CvFLAGS(cv) &= ~CVf_LVALUE)
127
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128#define CvASSERTION(cv) (CvFLAGS(cv) & CVf_ASSERTION)
129#define CvASSERTION_on(cv) (CvFLAGS(cv) |= CVf_ASSERTION)
130#define CvASSERTION_off(cv) (CvFLAGS(cv) &= ~CVf_ASSERTION)
131
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132#define CvEVAL(cv) (CvUNIQUE(cv) && !SvFAKE(cv))
133#define CvEVAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_off(cv))
134#define CvEVAL_off(cv) CvUNIQUE_off(cv)
135
bec31f9a 136/* BEGIN|CHECK|INIT|END */
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137#define CvSPECIAL(cv) (CvUNIQUE(cv) && SvFAKE(cv))
138#define CvSPECIAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_on(cv))
139#define CvSPECIAL_off(cv) (CvUNIQUE_off(cv),SvFAKE_off(cv))
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140
141#define CvCONST(cv) (CvFLAGS(cv) & CVf_CONST)
142#define CvCONST_on(cv) (CvFLAGS(cv) |= CVf_CONST)
143#define CvCONST_off(cv) (CvFLAGS(cv) &= ~CVf_CONST)
a4f1a029 144
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145#define CvWEAKOUTSIDE(cv) (CvFLAGS(cv) & CVf_WEAKOUTSIDE)
146#define CvWEAKOUTSIDE_on(cv) (CvFLAGS(cv) |= CVf_WEAKOUTSIDE)
147#define CvWEAKOUTSIDE_off(cv) (CvFLAGS(cv) &= ~CVf_WEAKOUTSIDE)
148
149
150/*
151=head1 CV reference counts and CvOUTSIDE
152
153=for apidoc m|bool|CvWEAKOUTSIDE|CV *cv
154
155Each CV has a pointer, C<CvOUTSIDE()>, to its lexically enclosing
156CV (if any). Because pointers to anonymous sub prototypes are
157stored in C<&> pad slots, it is a possible to get a circular reference,
158with the parent pointing to the child and vice-versa. To avoid the
159ensuing memory leak, we do not increment the reference count of the CV
160pointed to by C<CvOUTSIDE> in the I<one specific instance> that the parent
161has a C<&> pad slot pointing back to us. In this case, we set the
162C<CvWEAKOUTSIDE> flag in the child. This allows us to determine under what
163circumstances we should decrement the refcount of the parent when freeing
164the child.
165
166There is a further complication with non-closure anonymous subs (ie those
167that do not refer to any lexicals outside that sub). In this case, the
168anonymous prototype is shared rather than being cloned. This has the
169consequence that the parent may be freed while there are still active
170children, eg
171
172 BEGIN { $a = sub { eval '$x' } }
173
174In this case, the BEGIN is freed immediately after execution since there
175are no active references to it: the anon sub prototype has
176C<CvWEAKOUTSIDE> set since it's not a closure, and $a points to the same
177CV, so it doesn't contribute to BEGIN's refcount either. When $a is
178executed, the C<eval '$x'> causes the chain of C<CvOUTSIDE>s to be followed,
179and the freed BEGIN is accessed.
180
181To avoid this, whenever a CV and its associated pad is freed, any
182C<&> entries in the pad are explicitly removed from the pad, and if the
183refcount of the pointed-to anon sub is still positive, then that
184child's C<CvOUTSIDE> is set to point to its grandparent. This will only
185occur in the single specific case of a non-closure anon prototype
186having one or more active references (such as C<$a> above).
187
188One other thing to consider is that a CV may be merely undefined
189rather than freed, eg C<undef &foo>. In this case, its refcount may
190not have reached zero, but we still delete its pad and its C<CvROOT> etc.
191Since various children may still have their C<CvOUTSIDE> pointing at this
192undefined CV, we keep its own C<CvOUTSIDE> for the time being, so that
193the chain of lexical scopes is unbroken. For example, the following
194should print 123:
195
196 my $x = 123;
197 sub tmp { sub { eval '$x' } }
198 my $a = tmp();
199 undef &tmp;
200 print $a->();
201
202=cut
203*/