1 /* cv.h 2 * 3 * Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1999, 4 * 2000, 2001, 2002, 2003, 2004, by Larry Wall and others 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 * 9 */ 10 11 /* This structure must match XPVCV in B/C.pm and the beginning of XPVFM 12 * in sv.h */ 13 14 struct xpvcv { 15 char * xpv_pv; /* pointer to malloced string (for prototype) */ 16 STRLEN xpv_cur; /* length of xp_pv as a C string */ 17 STRLEN xpv_len; /* allocated size */ 18 IV xof_off; /* integer value */ 19 NV xnv_nv; /* numeric value, if any */ 20 MAGIC* xmg_magic; /* magic for scalar array */ 21 HV* xmg_stash; /* class package */ 22 23 HV * xcv_stash; 24 OP * xcv_start; 25 OP * xcv_root; 26 void (*xcv_xsub) (pTHX_ CV*); 27 ANY xcv_xsubany; 28 GV * xcv_gv; 29 char * xcv_file; 30 long xcv_depth; /* >= 2 indicates recursive call */ 31 PADLIST * xcv_padlist; 32 CV * xcv_outside; 33 #ifdef USE_5005THREADS 34 perl_mutex *xcv_mutexp; 35 struct perl_thread *xcv_owner; /* current owner thread */ 36 #endif /* USE_5005THREADS */ 37 cv_flags_t xcv_flags; 38 U32 xcv_outside_seq; /* the COP sequence (at the point of our 39 * compilation) in the lexically enclosing 40 * sub */ 41 }; 42 43 /* 44 =head1 Handy Values 45 46 =for apidoc AmU||Nullcv 47 Null CV pointer. 48 49 =head1 CV Manipulation Functions 50 51 =for apidoc Am|HV*|CvSTASH|CV* cv 52 Returns the stash of the CV. 53 54 =cut 55 */ 56 57 #define Nullcv Null(CV*) 58 59 #define CvSTASH(sv) ((XPVCV*)SvANY(sv))->xcv_stash 60 #define CvSTART(sv) ((XPVCV*)SvANY(sv))->xcv_start 61 #define CvROOT(sv) ((XPVCV*)SvANY(sv))->xcv_root 62 #define CvXSUB(sv) ((XPVCV*)SvANY(sv))->xcv_xsub 63 #define CvXSUBANY(sv) ((XPVCV*)SvANY(sv))->xcv_xsubany 64 #define CvGV(sv) ((XPVCV*)SvANY(sv))->xcv_gv 65 #define CvFILE(sv) ((XPVCV*)SvANY(sv))->xcv_file 66 #ifdef USE_ITHREADS 67 # define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = savepv(CopFILE(cop))) 68 #else 69 # define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = CopFILE(cop)) 70 #endif 71 #define CvFILEGV(sv) (gv_fetchfile(CvFILE(sv))) 72 #define CvDEPTH(sv) ((XPVCV*)SvANY(sv))->xcv_depth 73 #define CvPADLIST(sv) ((XPVCV*)SvANY(sv))->xcv_padlist 74 #define CvOUTSIDE(sv) ((XPVCV*)SvANY(sv))->xcv_outside 75 #ifdef USE_5005THREADS 76 #define CvMUTEXP(sv) ((XPVCV*)SvANY(sv))->xcv_mutexp 77 #define CvOWNER(sv) ((XPVCV*)SvANY(sv))->xcv_owner 78 #endif /* USE_5005THREADS */ 79 #define CvFLAGS(sv) ((XPVCV*)SvANY(sv))->xcv_flags 80 #define CvOUTSIDE_SEQ(sv) ((XPVCV*)SvANY(sv))->xcv_outside_seq 81 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 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 */ 90 #define CVf_NODEBUG 0x0020 /* no DB::sub indirection for this CV 91 (esp. useful for special XSUBs) */ 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 */ 94 #define CVf_LVALUE 0x0100 /* CV return value can be used as lvalue */ 95 #define CVf_CONST 0x0200 /* inlinable sub */ 96 #define CVf_WEAKOUTSIDE 0x0400 /* CvOUTSIDE isn't ref counted */ 97 98 /* This symbol for optimised communication between toke.c and op.c: */ 99 #define CVf_BUILTIN_ATTRS (CVf_METHOD|CVf_LOCKED|CVf_LVALUE) 100 101 #define CvCLONE(cv) (CvFLAGS(cv) & CVf_CLONE) 102 #define CvCLONE_on(cv) (CvFLAGS(cv) |= CVf_CLONE) 103 #define CvCLONE_off(cv) (CvFLAGS(cv) &= ~CVf_CLONE) 104 105 #define CvCLONED(cv) (CvFLAGS(cv) & CVf_CLONED) 106 #define CvCLONED_on(cv) (CvFLAGS(cv) |= CVf_CLONED) 107 #define CvCLONED_off(cv) (CvFLAGS(cv) &= ~CVf_CLONED) 108 109 #define CvANON(cv) (CvFLAGS(cv) & CVf_ANON) 110 #define CvANON_on(cv) (CvFLAGS(cv) |= CVf_ANON) 111 #define CvANON_off(cv) (CvFLAGS(cv) &= ~CVf_ANON) 112 113 #ifdef PERL_XSUB_OLDSTYLE 114 #define CvOLDSTYLE(cv) (CvFLAGS(cv) & CVf_OLDSTYLE) 115 #define CvOLDSTYLE_on(cv) (CvFLAGS(cv) |= CVf_OLDSTYLE) 116 #define CvOLDSTYLE_off(cv) (CvFLAGS(cv) &= ~CVf_OLDSTYLE) 117 #endif 118 119 #define CvUNIQUE(cv) (CvFLAGS(cv) & CVf_UNIQUE) 120 #define CvUNIQUE_on(cv) (CvFLAGS(cv) |= CVf_UNIQUE) 121 #define CvUNIQUE_off(cv) (CvFLAGS(cv) &= ~CVf_UNIQUE) 122 123 #define CvNODEBUG(cv) (CvFLAGS(cv) & CVf_NODEBUG) 124 #define CvNODEBUG_on(cv) (CvFLAGS(cv) |= CVf_NODEBUG) 125 #define CvNODEBUG_off(cv) (CvFLAGS(cv) &= ~CVf_NODEBUG) 126 127 #define CvMETHOD(cv) (CvFLAGS(cv) & CVf_METHOD) 128 #define CvMETHOD_on(cv) (CvFLAGS(cv) |= CVf_METHOD) 129 #define CvMETHOD_off(cv) (CvFLAGS(cv) &= ~CVf_METHOD) 130 131 #define CvLOCKED(cv) (CvFLAGS(cv) & CVf_LOCKED) 132 #define CvLOCKED_on(cv) (CvFLAGS(cv) |= CVf_LOCKED) 133 #define CvLOCKED_off(cv) (CvFLAGS(cv) &= ~CVf_LOCKED) 134 135 #define CvLVALUE(cv) (CvFLAGS(cv) & CVf_LVALUE) 136 #define CvLVALUE_on(cv) (CvFLAGS(cv) |= CVf_LVALUE) 137 #define CvLVALUE_off(cv) (CvFLAGS(cv) &= ~CVf_LVALUE) 138 139 #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) 142 143 /* BEGIN|CHECK|INIT|END */ 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)) 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) 151 152 #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 161 162 Each CV has a pointer, C<CvOUTSIDE()>, to its lexically enclosing 163 CV (if any). Because pointers to anonymous sub prototypes are 164 stored in C<&> pad slots, it is a possible to get a circular reference, 165 with the parent pointing to the child and vice-versa. To avoid the 166 ensuing memory leak, we do not increment the reference count of the CV 167 pointed to by C<CvOUTSIDE> in the I<one specific instance> that the parent 168 has a C<&> pad slot pointing back to us. In this case, we set the 169 C<CvWEAKOUTSIDE> flag in the child. This allows us to determine under what 170 circumstances we should decrement the refcount of the parent when freeing 171 the child. 172 173 There is a further complication with non-closure anonymous subs (ie those 174 that do not refer to any lexicals outside that sub). In this case, the 175 anonymous prototype is shared rather than being cloned. This has the 176 consequence that the parent may be freed while there are still active 177 children, eg 178 179 BEGIN { $a = sub { eval '$x' } } 180 181 In this case, the BEGIN is freed immediately after execution since there 182 are no active references to it: the anon sub prototype has 183 C<CvWEAKOUTSIDE> set since it's not a closure, and $a points to the same 184 CV, so it doesn't contribute to BEGIN's refcount either. When $a is 185 executed, the C<eval '$x'> causes the chain of C<CvOUTSIDE>s to be followed, 186 and the freed BEGIN is accessed. 187 188 To avoid this, whenever a CV and its associated pad is freed, any 189 C<&> entries in the pad are explicitly removed from the pad, and if the 190 refcount of the pointed-to anon sub is still positive, then that 191 child's C<CvOUTSIDE> is set to point to its grandparent. This will only 192 occur in the single specific case of a non-closure anon prototype 193 having one or more active references (such as C<$a> above). 194 195 One other thing to consider is that a CV may be merely undefined 196 rather than freed, eg C<undef &foo>. In this case, its refcount may 197 not have reached zero, but we still delete its pad and its C<CvROOT> etc. 198 Since various children may still have their C<CvOUTSIDE> pointing at this 199 undefined CV, we keep its own C<CvOUTSIDE> for the time being, so that 200 the chain of lexical scopes is unbroken. For example, the following 201 should 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 */ 211