1 /* cv.h 2 * 3 * Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1999, 2000, 2001, 4 * 2002, 2003, 2004, 2005, 2006, 2007, 2008 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 the beginning of XPVFM in sv.h */ 12 13 struct xpvcv { 14 _XPV_HEAD; 15 _XPVMG_HEAD; 16 _XPVCV_COMMON; 17 }; 18 19 /* 20 =head1 Handy Values 21 22 =for apidoc AmU||Nullcv 23 Null CV pointer. 24 25 (deprecated - use C<(CV *)NULL> instead) 26 27 =head1 CV Manipulation Functions 28 29 =for apidoc Am|HV*|CvSTASH|CV* cv 30 Returns the stash of the CV. 31 32 =cut 33 */ 34 35 #ifndef PERL_CORE 36 # define Nullcv Null(CV*) 37 #endif 38 39 #define CvSTASH(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_stash 40 #define CvSTART(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_start_u.xcv_start 41 #define CvROOT(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_root_u.xcv_root 42 #define CvXSUB(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_root_u.xcv_xsub 43 #define CvXSUBANY(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_start_u.xcv_xsubany 44 #define CvGV(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_gv 45 #define CvFILE(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_file 46 #ifdef USE_ITHREADS 47 # define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = savepv(CopFILE(cop))) 48 #else 49 # define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = CopFILE(cop)) 50 #endif 51 #define CvFILEGV(sv) (gv_fetchfile(CvFILE(sv))) 52 #if defined(__GNUC__) && !defined(PERL_GCC_BRACE_GROUPS_FORBIDDEN) 53 # define CvDEPTH(sv) (*({const CV *const _cvdepth = (const CV *)sv; \ 54 assert(SvTYPE(_cvdepth) == SVt_PVCV); \ 55 &((XPVCV*)SvANY(_cvdepth))->xiv_u.xivu_i32; \ 56 })) 57 #else 58 # define CvDEPTH(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xiv_u.xivu_i32 59 #endif 60 #define CvPADLIST(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_padlist 61 #define CvOUTSIDE(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_outside 62 #define CvFLAGS(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_flags 63 #define CvOUTSIDE_SEQ(sv) ((XPVCV*)MUTABLE_PTR(SvANY(sv)))->xcv_outside_seq 64 65 #define CVf_METHOD 0x0001 /* CV is explicitly marked as a method */ 66 #define CVf_LVALUE 0x0004 /* CV return value can be used as lvalue */ 67 68 #define CVf_WEAKOUTSIDE 0x0010 /* CvOUTSIDE isn't ref counted */ 69 #define CVf_CLONE 0x0020 /* anon CV uses external lexicals */ 70 #define CVf_CLONED 0x0040 /* a clone of one of those */ 71 #define CVf_ANON 0x0080 /* CvGV() can't be trusted */ 72 #define CVf_UNIQUE 0x0100 /* sub is only called once (eg PL_main_cv, 73 * require, eval). */ 74 #define CVf_NODEBUG 0x0200 /* no DB::sub indirection for this CV 75 (esp. useful for special XSUBs) */ 76 #define CVf_CONST 0x0400 /* inlinable sub */ 77 #define CVf_ISXSUB 0x0800 /* CV is an XSUB, not pure perl. */ 78 79 /* This symbol for optimised communication between toke.c and op.c: */ 80 #define CVf_BUILTIN_ATTRS (CVf_METHOD|CVf_LVALUE) 81 82 #define CvCLONE(cv) (CvFLAGS(cv) & CVf_CLONE) 83 #define CvCLONE_on(cv) (CvFLAGS(cv) |= CVf_CLONE) 84 #define CvCLONE_off(cv) (CvFLAGS(cv) &= ~CVf_CLONE) 85 86 #define CvCLONED(cv) (CvFLAGS(cv) & CVf_CLONED) 87 #define CvCLONED_on(cv) (CvFLAGS(cv) |= CVf_CLONED) 88 #define CvCLONED_off(cv) (CvFLAGS(cv) &= ~CVf_CLONED) 89 90 #define CvANON(cv) (CvFLAGS(cv) & CVf_ANON) 91 #define CvANON_on(cv) (CvFLAGS(cv) |= CVf_ANON) 92 #define CvANON_off(cv) (CvFLAGS(cv) &= ~CVf_ANON) 93 94 #define CvUNIQUE(cv) (CvFLAGS(cv) & CVf_UNIQUE) 95 #define CvUNIQUE_on(cv) (CvFLAGS(cv) |= CVf_UNIQUE) 96 #define CvUNIQUE_off(cv) (CvFLAGS(cv) &= ~CVf_UNIQUE) 97 98 #define CvNODEBUG(cv) (CvFLAGS(cv) & CVf_NODEBUG) 99 #define CvNODEBUG_on(cv) (CvFLAGS(cv) |= CVf_NODEBUG) 100 #define CvNODEBUG_off(cv) (CvFLAGS(cv) &= ~CVf_NODEBUG) 101 102 #define CvMETHOD(cv) (CvFLAGS(cv) & CVf_METHOD) 103 #define CvMETHOD_on(cv) (CvFLAGS(cv) |= CVf_METHOD) 104 #define CvMETHOD_off(cv) (CvFLAGS(cv) &= ~CVf_METHOD) 105 106 #define CvLVALUE(cv) (CvFLAGS(cv) & CVf_LVALUE) 107 #define CvLVALUE_on(cv) (CvFLAGS(cv) |= CVf_LVALUE) 108 #define CvLVALUE_off(cv) (CvFLAGS(cv) &= ~CVf_LVALUE) 109 110 #define CvEVAL(cv) (CvUNIQUE(cv) && !SvFAKE(cv)) 111 #define CvEVAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_off(cv)) 112 #define CvEVAL_off(cv) CvUNIQUE_off(cv) 113 114 /* BEGIN|CHECK|INIT|UNITCHECK|END */ 115 #define CvSPECIAL(cv) (CvUNIQUE(cv) && SvFAKE(cv)) 116 #define CvSPECIAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_on(cv)) 117 #define CvSPECIAL_off(cv) (CvUNIQUE_off(cv),SvFAKE_off(cv)) 118 119 #define CvCONST(cv) (CvFLAGS(cv) & CVf_CONST) 120 #define CvCONST_on(cv) (CvFLAGS(cv) |= CVf_CONST) 121 #define CvCONST_off(cv) (CvFLAGS(cv) &= ~CVf_CONST) 122 123 #define CvWEAKOUTSIDE(cv) (CvFLAGS(cv) & CVf_WEAKOUTSIDE) 124 #define CvWEAKOUTSIDE_on(cv) (CvFLAGS(cv) |= CVf_WEAKOUTSIDE) 125 #define CvWEAKOUTSIDE_off(cv) (CvFLAGS(cv) &= ~CVf_WEAKOUTSIDE) 126 127 #define CvISXSUB(cv) (CvFLAGS(cv) & CVf_ISXSUB) 128 #define CvISXSUB_on(cv) (CvFLAGS(cv) |= CVf_ISXSUB) 129 #define CvISXSUB_off(cv) (CvFLAGS(cv) &= ~CVf_ISXSUB) 130 131 /* Flags for newXS_flags */ 132 #define XS_DYNAMIC_FILENAME 0x01 /* The filename isn't static */ 133 134 /* 135 =head1 CV reference counts and CvOUTSIDE 136 137 =for apidoc m|bool|CvWEAKOUTSIDE|CV *cv 138 139 Each CV has a pointer, C<CvOUTSIDE()>, to its lexically enclosing 140 CV (if any). Because pointers to anonymous sub prototypes are 141 stored in C<&> pad slots, it is a possible to get a circular reference, 142 with the parent pointing to the child and vice-versa. To avoid the 143 ensuing memory leak, we do not increment the reference count of the CV 144 pointed to by C<CvOUTSIDE> in the I<one specific instance> that the parent 145 has a C<&> pad slot pointing back to us. In this case, we set the 146 C<CvWEAKOUTSIDE> flag in the child. This allows us to determine under what 147 circumstances we should decrement the refcount of the parent when freeing 148 the child. 149 150 There is a further complication with non-closure anonymous subs (i.e. those 151 that do not refer to any lexicals outside that sub). In this case, the 152 anonymous prototype is shared rather than being cloned. This has the 153 consequence that the parent may be freed while there are still active 154 children, eg 155 156 BEGIN { $a = sub { eval '$x' } } 157 158 In this case, the BEGIN is freed immediately after execution since there 159 are no active references to it: the anon sub prototype has 160 C<CvWEAKOUTSIDE> set since it's not a closure, and $a points to the same 161 CV, so it doesn't contribute to BEGIN's refcount either. When $a is 162 executed, the C<eval '$x'> causes the chain of C<CvOUTSIDE>s to be followed, 163 and the freed BEGIN is accessed. 164 165 To avoid this, whenever a CV and its associated pad is freed, any 166 C<&> entries in the pad are explicitly removed from the pad, and if the 167 refcount of the pointed-to anon sub is still positive, then that 168 child's C<CvOUTSIDE> is set to point to its grandparent. This will only 169 occur in the single specific case of a non-closure anon prototype 170 having one or more active references (such as C<$a> above). 171 172 One other thing to consider is that a CV may be merely undefined 173 rather than freed, eg C<undef &foo>. In this case, its refcount may 174 not have reached zero, but we still delete its pad and its C<CvROOT> etc. 175 Since various children may still have their C<CvOUTSIDE> pointing at this 176 undefined CV, we keep its own C<CvOUTSIDE> for the time being, so that 177 the chain of lexical scopes is unbroken. For example, the following 178 should print 123: 179 180 my $x = 123; 181 sub tmp { sub { eval '$x' } } 182 my $a = tmp(); 183 undef &tmp; 184 print $a->(); 185 186 =cut 187 */ 188 189 /* 190 * Local variables: 191 * c-indentation-style: bsd 192 * c-basic-offset: 4 193 * indent-tabs-mode: t 194 * End: 195 * 196 * ex: set ts=8 sts=4 sw=4 noet: 197 */ 198