gcc/cp/tinfo.cc

   1 // Methods for type_info for -*- C++ -*- Run Time Type Identification.
   2 // Copyright (C) 1994, 1996, 1998, 1999 Free Software Foundation
   3
   4 // This file is part of GNU CC.
   5
   6 // GNU CC is free software; you can redistribute it and/or modify
   7 // it under the terms of the GNU General Public License as published by
   8 // the Free Software Foundation; either version 2, or (at your option)
   9 // any later version.
  10
  11 // GNU CC is distributed in the hope that it will be useful,
  12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 // GNU General Public License for more details.
  15
  16 // You should have received a copy of the GNU General Public License
  17 // along with GNU CC; see the file COPYING.  If not, write to
  18 // the Free Software Foundation, 59 Temple Place - Suite 330,
  19 // Boston, MA 02111-1307, USA.
  20
  21 // As a special exception, if you link this library with other files,
  22 // some of which are compiled with GCC, to produce an executable,
  23 // this library does not by itself cause the resulting executable
  24 // to be covered by the GNU General Public License.
  25 // This exception does not however invalidate any other reasons why
  26 // the executable file might be covered by the GNU General Public License.
  27
  28 #pragma implementation "typeinfo"
  29
  30 #include <stddef.h>
  31 #include "tinfo.h"
  32 #include "new"                  // for placement new
  33
  34 // This file contains the minimal working set necessary to link with code
  35 // that uses virtual functions and -frtti but does not actually use RTTI
  36 // functionality.
  37
  38 std::type_info::
  39 ~type_info ()
  40 { }
  41
  42 // We can't rely on common symbols being shared between shared objects.
  43 bool std::type_info::
  44 operator== (const std::type_info& arg) const
  45 {
  46   return (&arg == this) || (strcmp (name (), arg.name ()) == 0);
  47 }
  48
  49 extern "C" void
  50 __rtti_class (void *addr, const char *name,
  51               const __class_type_info::base_info *bl, size_t bn)
  52 { new (addr) __class_type_info (name, bl, bn); }
  53
  54 extern "C" void
  55 __rtti_si (void *addr, const char *n, const std::type_info *ti)
  56 {
  57   new (addr) __si_type_info
  58     (n, static_cast <const __user_type_info &> (*ti));
  59 }
  60
  61 extern "C" void
  62 __rtti_user (void *addr, const char *name)
  63 { new (addr) __user_type_info (name); }
  64
  65 // dynamic_cast helper methods.
  66 // Returns 1 if the cast succeeds, 0 otherwise.  Stores the adjusted value
  67 // in VALP.
  68
  69 int __user_type_info::
  70 dcast (const type_info& to, int, void *addr, void **valp,
  71        const type_info *, void *) const
  72 {
  73   *valp = addr;
  74   return (*this == to);
  75 }
  76
  77 int __si_type_info::
  78 dcast (const type_info& to, int require_public, void *addr, void **valp,
  79        const type_info *sub, void *subptr) const
  80 {
  81   if (*this == to)
  82     {
  83       *valp = addr;
  84       return 1;
  85     }
  86   return base.dcast (to, require_public, addr, valp, sub, subptr);
  87 }
  88
  89 int __class_type_info::
  90 dcast (const type_info& desired, int is_public, void *objptr, void **valp,
  91        const type_info *sub, void *subptr) const
  92 {
  93   *valp = objptr;
  94
  95   if (*this == desired)
  96     return 1;
  97
  98   int match_found = 0;
  99   void *match = 0;
 100
 101   for (size_t i = 0; i < n_bases; i++)
 102     {
 103       if (is_public && base_list[i].access != PUBLIC)
 104         continue;
 105
 106       void *p;
 107
 108       if (objptr)
 109         {
 110           p = (char *)objptr + base_list[i].offset;
 111           if (base_list[i].is_virtual)
 112             p = *(void **)p;
 113         }
 114       else
 115         /* Preserve null pointer.  */
 116         p = objptr;
 117
 118       if (base_list[i].base->dcast (desired, is_public, p, &p, sub, subptr))
 119         {
 120           if (! match_found)
 121             {
 122               match_found = 1;
 123               match = p;
 124             }
 125           else if (match != p)
 126             {
 127               if (sub)
 128                 {
 129                   // Perhaps we're downcasting from *sub to desired; see if
 130                   // subptr is a subobject of exactly one of {match_found,p}.
 131
 132                   const __user_type_info &d =
 133                     static_cast <const __user_type_info &> (desired);
 134
 135                   void *os;
 136                   d.dcast (*sub, 1, match, &os);
 137                   void *ns;
 138                   d.dcast (*sub, 1, p, &ns);
 139
 140                   if (os == ns)
 141                     // Both have the same subobject, so we can't disambiguate;
 142                     // i.e. subptr is a virtual base.
 143                     return 0;
 144                   else if (os == subptr)
 145                     continue;
 146                   else if (ns == subptr)
 147                     {
 148                       match = p;
 149                       continue;
 150                     }
 151                 }
 152               else
 153                 // We're not downcasting, so we can't disambiguate.
 154                 return 0;
 155             }
 156         }
 157     }
 158
 159   *valp = match;
 160   return match_found;
 161 }