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1 | /* cv.h |
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2 | * |
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3 | * Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1999, |
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4 | * 2000, 2001, 2002, 2003, 2004, 2005, 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 | |
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11 | /* This structure must match XPVCV in B/C.pm and the beginning of XPVFM |
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12 | * in sv.h */ |
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13 | |
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14 | struct xpvcv { |
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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 */ |
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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; |
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26 | NV xnvu_nv; /* numeric value, if any */ |
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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; |
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34 | void (*xcv_xsub) (pTHX_ CV*); |
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35 | ANY xcv_xsubany; |
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36 | GV * xcv_gv; |
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37 | char * xcv_file; |
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38 | long xcv_depth; /* >= 2 indicates recursive call */ |
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39 | PADLIST * xcv_padlist; |
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40 | CV * xcv_outside; |
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41 | cv_flags_t xcv_flags; |
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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 */ |
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45 | }; |
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46 | |
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47 | /* |
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48 | =head1 Handy Values |
49 | |
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50 | =for apidoc AmU||Nullcv |
51 | Null 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 |
56 | Returns the stash of the CV. |
57 | |
58 | =cut |
59 | */ |
60 | |
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61 | #define Nullcv Null(CV*) |
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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 |
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68 | #define CvGV(sv) ((XPVCV*)SvANY(sv))->xcv_gv |
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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 |
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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 |
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78 | #define CvOUTSIDE(sv) ((XPVCV*)SvANY(sv))->xcv_outside |
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79 | #define CvFLAGS(sv) ((XPVCV*)SvANY(sv))->xcv_flags |
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80 | #define CvOUTSIDE_SEQ(sv) ((XPVCV*)SvANY(sv))->xcv_outside_seq |
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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 */ |
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90 | #define CVf_NODEBUG 0x0020 /* no DB::sub indirection for this CV |
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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 */ |
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94 | #define CVf_LVALUE 0x0100 /* CV return value can be used as lvalue */ |
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95 | #define CVf_CONST 0x0200 /* inlinable sub */ |
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96 | #define CVf_WEAKOUTSIDE 0x0400 /* CvOUTSIDE isn't ref counted */ |
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97 | #define CVf_ASSERTION 0x0800 /* CV called only when asserting */ |
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98 | |
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99 | /* This symbol for optimised communication between toke.c and op.c: */ |
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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) |
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113 | |
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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) |
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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) |
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135 | |
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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 | |
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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) |
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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 | |
167 | Each CV has a pointer, C<CvOUTSIDE()>, to its lexically enclosing |
168 | CV (if any). Because pointers to anonymous sub prototypes are |
169 | stored in C<&> pad slots, it is a possible to get a circular reference, |
170 | with the parent pointing to the child and vice-versa. To avoid the |
171 | ensuing memory leak, we do not increment the reference count of the CV |
172 | pointed to by C<CvOUTSIDE> in the I<one specific instance> that the parent |
173 | has a C<&> pad slot pointing back to us. In this case, we set the |
174 | C<CvWEAKOUTSIDE> flag in the child. This allows us to determine under what |
175 | circumstances we should decrement the refcount of the parent when freeing |
176 | the child. |
177 | |
178 | There is a further complication with non-closure anonymous subs (ie those |
179 | that do not refer to any lexicals outside that sub). In this case, the |
180 | anonymous prototype is shared rather than being cloned. This has the |
181 | consequence that the parent may be freed while there are still active |
182 | children, eg |
183 | |
184 | BEGIN { $a = sub { eval '$x' } } |
185 | |
186 | In this case, the BEGIN is freed immediately after execution since there |
187 | are no active references to it: the anon sub prototype has |
188 | C<CvWEAKOUTSIDE> set since it's not a closure, and $a points to the same |
189 | CV, so it doesn't contribute to BEGIN's refcount either. When $a is |
190 | executed, the C<eval '$x'> causes the chain of C<CvOUTSIDE>s to be followed, |
191 | and the freed BEGIN is accessed. |
192 | |
193 | To avoid this, whenever a CV and its associated pad is freed, any |
194 | C<&> entries in the pad are explicitly removed from the pad, and if the |
195 | refcount of the pointed-to anon sub is still positive, then that |
196 | child's C<CvOUTSIDE> is set to point to its grandparent. This will only |
197 | occur in the single specific case of a non-closure anon prototype |
198 | having one or more active references (such as C<$a> above). |
199 | |
200 | One other thing to consider is that a CV may be merely undefined |
201 | rather than freed, eg C<undef &foo>. In this case, its refcount may |
202 | not have reached zero, but we still delete its pad and its C<CvROOT> etc. |
203 | Since various children may still have their C<CvOUTSIDE> pointing at this |
204 | undefined CV, we keep its own C<CvOUTSIDE> for the time being, so that |
205 | the chain of lexical scopes is unbroken. For example, the following |
206 | should 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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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 | */ |