| 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, by Larry Wall and others
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| 5 | *
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| 6 | * You may distribute under the terms of either the GNU General Public
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| 7 | * License or the Artistic License, as specified in the README file.
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| 8 | *
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| 9 | */
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| 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 | char * xpv_pv; /* pointer to malloced string (for prototype) */
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| 16 | STRLEN xpv_cur; /* length of xp_pv as a C string */
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| 17 | STRLEN xpv_len; /* allocated size */
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| 18 | IV xof_off; /* integer value */
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| 19 | NV xnv_nv; /* numeric value, if any */
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| 20 | MAGIC* xmg_magic; /* magic for scalar array */
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| 21 | HV* xmg_stash; /* class package */
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| 22 |
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| 23 | HV * xcv_stash;
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| 24 | OP * xcv_start;
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| 25 | OP * xcv_root;
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| 26 | void (*xcv_xsub) (pTHX_ CV*);
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| 27 | ANY xcv_xsubany;
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| 28 | GV * xcv_gv;
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| 29 | char * xcv_file;
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| 30 | long xcv_depth; /* >= 2 indicates recursive call */
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| 31 | PADLIST * xcv_padlist;
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| 32 | CV * xcv_outside;
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| 33 | #ifdef USE_5005THREADS
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| 34 | perl_mutex *xcv_mutexp;
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| 35 | struct perl_thread *xcv_owner; /* current owner thread */
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| 36 | #endif /* USE_5005THREADS */
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| 37 | cv_flags_t xcv_flags;
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| 38 | U32 xcv_outside_seq; /* the COP sequence (at the point of our
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| 39 | * compilation) in the lexically enclosing
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| 40 | * sub */
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| 41 | };
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| 42 |
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| 43 | /*
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| 44 | =head1 Handy Values
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| 45 |
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| 46 | =for apidoc AmU||Nullcv
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| 47 | Null CV pointer.
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| 48 |
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| 49 | =head1 CV Manipulation Functions
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| 50 |
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| 51 | =for apidoc Am|HV*|CvSTASH|CV* cv
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| 52 | Returns the stash of the CV.
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| 53 |
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| 54 | =cut
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| 55 | */
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| 56 |
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| 57 | #define Nullcv Null(CV*)
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| 58 |
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| 59 | #define CvSTASH(sv) ((XPVCV*)SvANY(sv))->xcv_stash
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| 60 | #define CvSTART(sv) ((XPVCV*)SvANY(sv))->xcv_start
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| 61 | #define CvROOT(sv) ((XPVCV*)SvANY(sv))->xcv_root
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| 62 | #define CvXSUB(sv) ((XPVCV*)SvANY(sv))->xcv_xsub
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| 63 | #define CvXSUBANY(sv) ((XPVCV*)SvANY(sv))->xcv_xsubany
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| 64 | #define CvGV(sv) ((XPVCV*)SvANY(sv))->xcv_gv
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| 65 | #define CvFILE(sv) ((XPVCV*)SvANY(sv))->xcv_file
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| 66 | #ifdef USE_ITHREADS
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| 67 | # define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = savepv(CopFILE(cop)))
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| 68 | #else
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| 69 | # define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = CopFILE(cop))
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| 70 | #endif
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| 71 | #define CvFILEGV(sv) (gv_fetchfile(CvFILE(sv)))
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| 72 | #define CvDEPTH(sv) ((XPVCV*)SvANY(sv))->xcv_depth
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| 73 | #define CvPADLIST(sv) ((XPVCV*)SvANY(sv))->xcv_padlist
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| 74 | #define CvOUTSIDE(sv) ((XPVCV*)SvANY(sv))->xcv_outside
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| 75 | #ifdef USE_5005THREADS
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| 76 | #define CvMUTEXP(sv) ((XPVCV*)SvANY(sv))->xcv_mutexp
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| 77 | #define CvOWNER(sv) ((XPVCV*)SvANY(sv))->xcv_owner
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| 78 | #endif /* USE_5005THREADS */
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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 */
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| 83 | #define CVf_CLONED 0x0002 /* a clone of one of those */
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| 84 | #define CVf_ANON 0x0004 /* CvGV() can't be trusted */
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| 85 | #define CVf_OLDSTYLE 0x0008
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| 86 | #define CVf_UNIQUE 0x0010 /* sub is only called once (eg PL_main_cv,
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| 87 | * require, eval). Not to be confused
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| 88 | * with the GVf_UNIQUE flag associated
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| 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 */
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| 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 |
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| 98 | /* This symbol for optimised communication between toke.c and op.c: */
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| 99 | #define CVf_BUILTIN_ATTRS (CVf_METHOD|CVf_LOCKED|CVf_LVALUE)
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| 100 |
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| 101 | #define CvCLONE(cv) (CvFLAGS(cv) & CVf_CLONE)
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| 102 | #define CvCLONE_on(cv) (CvFLAGS(cv) |= CVf_CLONE)
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| 103 | #define CvCLONE_off(cv) (CvFLAGS(cv) &= ~CVf_CLONE)
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| 104 |
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| 105 | #define CvCLONED(cv) (CvFLAGS(cv) & CVf_CLONED)
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| 106 | #define CvCLONED_on(cv) (CvFLAGS(cv) |= CVf_CLONED)
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| 107 | #define CvCLONED_off(cv) (CvFLAGS(cv) &= ~CVf_CLONED)
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| 108 |
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| 109 | #define CvANON(cv) (CvFLAGS(cv) & CVf_ANON)
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| 110 | #define CvANON_on(cv) (CvFLAGS(cv) |= CVf_ANON)
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| 111 | #define CvANON_off(cv) (CvFLAGS(cv) &= ~CVf_ANON)
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| 112 |
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| 113 | #ifdef PERL_XSUB_OLDSTYLE
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| 114 | #define CvOLDSTYLE(cv) (CvFLAGS(cv) & CVf_OLDSTYLE)
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| 115 | #define CvOLDSTYLE_on(cv) (CvFLAGS(cv) |= CVf_OLDSTYLE)
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| 116 | #define CvOLDSTYLE_off(cv) (CvFLAGS(cv) &= ~CVf_OLDSTYLE)
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| 117 | #endif
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| 118 |
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| 119 | #define CvUNIQUE(cv) (CvFLAGS(cv) & CVf_UNIQUE)
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| 120 | #define CvUNIQUE_on(cv) (CvFLAGS(cv) |= CVf_UNIQUE)
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| 121 | #define CvUNIQUE_off(cv) (CvFLAGS(cv) &= ~CVf_UNIQUE)
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| 122 |
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| 123 | #define CvNODEBUG(cv) (CvFLAGS(cv) & CVf_NODEBUG)
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| 124 | #define CvNODEBUG_on(cv) (CvFLAGS(cv) |= CVf_NODEBUG)
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| 125 | #define CvNODEBUG_off(cv) (CvFLAGS(cv) &= ~CVf_NODEBUG)
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| 126 |
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| 127 | #define CvMETHOD(cv) (CvFLAGS(cv) & CVf_METHOD)
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| 128 | #define CvMETHOD_on(cv) (CvFLAGS(cv) |= CVf_METHOD)
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| 129 | #define CvMETHOD_off(cv) (CvFLAGS(cv) &= ~CVf_METHOD)
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| 130 |
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| 131 | #define CvLOCKED(cv) (CvFLAGS(cv) & CVf_LOCKED)
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| 132 | #define CvLOCKED_on(cv) (CvFLAGS(cv) |= CVf_LOCKED)
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| 133 | #define CvLOCKED_off(cv) (CvFLAGS(cv) &= ~CVf_LOCKED)
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| 134 |
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| 135 | #define CvLVALUE(cv) (CvFLAGS(cv) & CVf_LVALUE)
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| 136 | #define CvLVALUE_on(cv) (CvFLAGS(cv) |= CVf_LVALUE)
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| 137 | #define CvLVALUE_off(cv) (CvFLAGS(cv) &= ~CVf_LVALUE)
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| 138 |
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| 139 | #define CvEVAL(cv) (CvUNIQUE(cv) && !SvFAKE(cv))
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| 140 | #define CvEVAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_off(cv))
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| 141 | #define CvEVAL_off(cv) CvUNIQUE_off(cv)
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| 142 |
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| 143 | /* BEGIN|CHECK|INIT|END */
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| 144 | #define CvSPECIAL(cv) (CvUNIQUE(cv) && SvFAKE(cv))
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| 145 | #define CvSPECIAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_on(cv))
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| 146 | #define CvSPECIAL_off(cv) (CvUNIQUE_off(cv),SvFAKE_off(cv))
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| 147 |
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| 148 | #define CvCONST(cv) (CvFLAGS(cv) & CVf_CONST)
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| 149 | #define CvCONST_on(cv) (CvFLAGS(cv) |= CVf_CONST)
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| 150 | #define CvCONST_off(cv) (CvFLAGS(cv) &= ~CVf_CONST)
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| 151 |
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| 152 | #define CvWEAKOUTSIDE(cv) (CvFLAGS(cv) & CVf_WEAKOUTSIDE)
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| 153 | #define CvWEAKOUTSIDE_on(cv) (CvFLAGS(cv) |= CVf_WEAKOUTSIDE)
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| 154 | #define CvWEAKOUTSIDE_off(cv) (CvFLAGS(cv) &= ~CVf_WEAKOUTSIDE)
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| 155 |
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| 156 |
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| 157 | /*
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| 158 | =head1 CV reference counts and CvOUTSIDE
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| 159 |
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| 160 | =for apidoc m|bool|CvWEAKOUTSIDE|CV *cv
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| 161 |
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| 162 | Each CV has a pointer, C<CvOUTSIDE()>, to its lexically enclosing
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| 163 | CV (if any). Because pointers to anonymous sub prototypes are
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| 164 | stored in C<&> pad slots, it is a possible to get a circular reference,
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| 165 | with the parent pointing to the child and vice-versa. To avoid the
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| 166 | ensuing memory leak, we do not increment the reference count of the CV
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| 167 | pointed to by C<CvOUTSIDE> in the I<one specific instance> that the parent
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| 168 | has a C<&> pad slot pointing back to us. In this case, we set the
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| 169 | C<CvWEAKOUTSIDE> flag in the child. This allows us to determine under what
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| 170 | circumstances we should decrement the refcount of the parent when freeing
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| 171 | the child.
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| 172 |
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| 173 | There is a further complication with non-closure anonymous subs (i.e. those
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| 174 | that do not refer to any lexicals outside that sub). In this case, the
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| 175 | anonymous prototype is shared rather than being cloned. This has the
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| 176 | consequence that the parent may be freed while there are still active
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| 177 | children, eg
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| 178 |
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| 179 | BEGIN { $a = sub { eval '$x' } }
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| 180 |
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| 181 | In this case, the BEGIN is freed immediately after execution since there
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| 182 | are no active references to it: the anon sub prototype has
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| 183 | C<CvWEAKOUTSIDE> set since it's not a closure, and $a points to the same
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| 184 | CV, so it doesn't contribute to BEGIN's refcount either. When $a is
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| 185 | executed, the C<eval '$x'> causes the chain of C<CvOUTSIDE>s to be followed,
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| 186 | and the freed BEGIN is accessed.
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| 187 |
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| 188 | To avoid this, whenever a CV and its associated pad is freed, any
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| 189 | C<&> entries in the pad are explicitly removed from the pad, and if the
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| 190 | refcount of the pointed-to anon sub is still positive, then that
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| 191 | child's C<CvOUTSIDE> is set to point to its grandparent. This will only
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| 192 | occur in the single specific case of a non-closure anon prototype
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| 193 | having one or more active references (such as C<$a> above).
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| 194 |
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| 195 | One other thing to consider is that a CV may be merely undefined
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| 196 | rather than freed, eg C<undef &foo>. In this case, its refcount may
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| 197 | not have reached zero, but we still delete its pad and its C<CvROOT> etc.
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| 198 | Since various children may still have their C<CvOUTSIDE> pointing at this
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| 199 | undefined CV, we keep its own C<CvOUTSIDE> for the time being, so that
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| 200 | the chain of lexical scopes is unbroken. For example, the following
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| 201 | should print 123:
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| 202 |
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| 203 | my $x = 123;
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| 204 | sub tmp { sub { eval '$x' } }
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| 205 | my $a = tmp();
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| 206 | undef &tmp;
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| 207 | print $a->();
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| 208 |
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| 209 | =cut
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| 210 | */
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