gcc/cp/tinfo.cc

   1 // Methods for type_info for -*- C++ -*- Run Time Type Identification.
   2 // Copyright (C) 1994, 1996 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 #include <stddef.h>
  29 #include "tinfo.h"
  30 #include "new"                  // for placement new
  31
  32 // This file contains the minimal working set necessary to link with code
  33 // that uses virtual functions and -frtti but does not actually use RTTI
  34 // functionality.
  35
  36 type_info::
  37 ~type_info ()
  38 { }
  39
  40 extern "C" void
  41 __rtti_class (void *addr, const char *name,
  42               const __class_type_info::base_info *bl, size_t bn)
  43 { new (addr) __class_type_info (name, bl, bn); }
  44
  45 extern "C" void
  46 __rtti_si (void *addr, const char *n, const type_info *ti)
  47 {
  48   new (addr) __si_type_info
  49     (n, static_cast <const __user_type_info &> (*ti));
  50 }
  51
  52 extern "C" void
  53 __rtti_user (void *addr, const char *name)
  54 { new (addr) __user_type_info (name); }
  55
  56 // dynamic_cast helper methods.
  57 // Returns a pointer to the desired sub-object or 0.
  58
  59 void * __user_type_info::
  60 dcast (const type_info& to, int, void *addr, const type_info *, void *) const
  61 { return (*this == to) ? addr : 0; }
  62
  63 void * __si_type_info::
  64 dcast (const type_info& to, int require_public, void *addr,
  65        const type_info *sub, void *subptr) const
  66 {
  67   if (*this == to)
  68     return addr;
  69   return base.dcast (to, require_public, addr, sub, subptr);
  70 }
  71
  72 void* __class_type_info::
  73 dcast (const type_info& desired, int is_public, void *objptr,
  74        const type_info *sub, void *subptr) const
  75 {
  76   if (*this == desired)
  77     return objptr;
  78
  79   void *match_found = 0;
  80   for (int i = 0; i < n_bases; i++)
  81     {
  82       if (is_public && base_list[i].access != PUBLIC)
  83         continue;
  84
  85       void *p = (char *)objptr + base_list[i].offset;
  86       if (base_list[i].is_virtual)
  87         p = *(void **)p;
  88       p = base_list[i].base->dcast (desired, is_public, p, sub, subptr);
  89       if (p)
  90         {
  91           if (match_found == 0)
  92             match_found = p;
  93           else if (match_found != p)
  94             {
  95               if (sub)
  96                 {
  97                   // Perhaps we're downcasting from *sub to desired; see if
  98                   // subptr is a subobject of exactly one of {match_found,p}.
  99
 100                   const __user_type_info &d =
 101                     static_cast <const __user_type_info &> (desired);
 102
 103                   void *os = d.dcast (*sub, 1, match_found);
 104                   void *ns = d.dcast (*sub, 1, p);
 105
 106                   if (os == ns)
 107                     /* ambiguous -- subptr is a virtual base */;
 108                   else if (os == subptr)
 109                     continue;
 110                   else if (ns == subptr)
 111                     {
 112                       match_found = p;
 113                       continue;
 114                     }
 115                 }
 116
 117               // base found at two different pointers,
 118               // conversion is not unique
 119               return 0;
 120             }
 121         }
 122     }
 123
 124   return match_found;
 125 }