lib/perl5/5.8.8/msys/CORE/cv.h

   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 (i.e. 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 */