libstdc++-v3/libsupc++/typeinfo

   1 // RTTI support for -*- C++ -*-
   2 // Copyright (C) 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002,
   3 // 2003, 2004, 2005, 2006, 2007, 2009
   4 // Free Software Foundation
   5 //
   6 // This file is part of GCC.
   7 //
   8 // GCC is free software; you can redistribute it and/or modify
   9 // it under the terms of the GNU General Public License as published by
  10 // the Free Software Foundation; either version 3, or (at your option)
  11 // any later version.
  12 //
  13 // GCC is distributed in the hope that it will be useful,
  14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 // GNU General Public License for more details.
  17 //
  18 // Under Section 7 of GPL version 3, you are granted additional
  19 // permissions described in the GCC Runtime Library Exception, version
  20 // 3.1, as published by the Free Software Foundation.
  21
  22 // You should have received a copy of the GNU General Public License and
  23 // a copy of the GCC Runtime Library Exception along with this program;
  24 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  25 // <http://www.gnu.org/licenses/>.
  26
  27 /** @file typeinfo
  28  *  This is a Standard C++ Library header.
  29  */
  30
  31 #ifndef _TYPEINFO
  32 #define _TYPEINFO
  33
  34 #include <exception>
  35
  36 #pragma GCC visibility push(default)
  37
  38 extern "C++" {
  39
  40 namespace __cxxabiv1
  41 {
  42   class __class_type_info;
  43 } // namespace __cxxabiv1
  44
  45 // Determine whether typeinfo names for the same type are merged (in which
  46 // case comparison can just compare pointers) or not (in which case strings
  47 // must be compared), and whether comparison is to be implemented inline or
  48 // not.  We used to do inline pointer comparison by default if weak symbols
  49 // are available, but even with weak symbols sometimes names are not merged
  50 // when objects are loaded with RTLD_LOCAL, so now we always use strcmp by
  51 // default.  For ABI compatibility, we do the strcmp inline if weak symbols
  52 // are available, and out-of-line if not.  Out-of-line pointer comparison
  53 // is used where the object files are to be portable to multiple systems,
  54 // some of which may not be able to use pointer comparison, but the
  55 // particular system for which libstdc++ is being built can use pointer
  56 // comparison; in particular for most ARM EABI systems, where the ABI
  57 // specifies out-of-line comparison.  The compiler's target configuration
  58 // can override the defaults by defining __GXX_TYPEINFO_EQUALITY_INLINE to
  59 // 1 or 0 to indicate whether or not comparison is inline, and
  60 // __GXX_MERGED_TYPEINFO_NAMES to 1 or 0 to indicate whether or not pointer
  61 // comparison can be used.
  62
  63 #ifndef __GXX_MERGED_TYPEINFO_NAMES
  64 // By default, typeinfo names are not merged.
  65 #define __GXX_MERGED_TYPEINFO_NAMES 0
  66 #endif
  67
  68 // By default follow the old inline rules to avoid ABI changes.
  69 #ifndef __GXX_TYPEINFO_EQUALITY_INLINE
  70   #if !__GXX_WEAK__
  71     #define __GXX_TYPEINFO_EQUALITY_INLINE 0
  72   #else
  73     #define __GXX_TYPEINFO_EQUALITY_INLINE 1
  74   #endif
  75 #endif
  76
  77 namespace std
  78 {
  79   /**
  80    *  @brief  Part of RTTI.
  81    *
  82    *  The @c type_info class describes type information generated by
  83    *  an implementation.
  84   */
  85   class type_info
  86   {
  87   public:
  88     /** Destructor first. Being the first non-inline virtual function, this
  89      *  controls in which translation unit the vtable is emitted. The
  90      *  compiler makes use of that information to know where to emit
  91      *  the runtime-mandated type_info structures in the new-abi.  */
  92     virtual ~type_info();
  93
  94     /** Returns an @e implementation-defined byte string; this is not
  95      *  portable between compilers!  */
  96     const char* name() const
  97     { return __name; }
  98
  99 #if !__GXX_TYPEINFO_EQUALITY_INLINE
 100     // In old abi, or when weak symbols are not supported, there can
 101     // be multiple instances of a type_info object for one
 102     // type. Uniqueness must use the _name value, not object address.
 103     bool before(const type_info& __arg) const;
 104     bool operator==(const type_info& __arg) const;
 105 #else
 106   #if !__GXX_MERGED_TYPEINFO_NAMES
 107     /** Returns true if @c *this precedes @c __arg in the implementation's
 108      *  collation order.  */
 109     // Even with the new abi, on systems that support dlopen
 110     // we can run into cases where type_info names aren't merged,
 111     // so we still need to do string comparison.
 112     bool before(const type_info& __arg) const
 113     { return __builtin_strcmp (__name, __arg.__name) < 0; }
 114
 115     bool operator==(const type_info& __arg) const
 116     {
 117       return ((__name == __arg.__name)
 118               || __builtin_strcmp (__name, __arg.__name) == 0);
 119     }
 120   #else
 121     // On some targets we can rely on type_info's NTBS being unique,
 122     // and therefore address comparisons are sufficient.
 123     bool before(const type_info& __arg) const
 124     { return __name < __arg.__name; }
 125
 126     bool operator==(const type_info& __arg) const
 127     { return __name == __arg.__name; }
 128   #endif
 129 #endif
 130     bool operator!=(const type_info& __arg) const
 131     { return !operator==(__arg); }
 132
 133     // Return true if this is a pointer type of some kind
 134     virtual bool __is_pointer_p() const;
 135
 136     // Return true if this is a function type
 137     virtual bool __is_function_p() const;
 138
 139     // Try and catch a thrown type. Store an adjusted pointer to the
 140     // caught type in THR_OBJ. If THR_TYPE is not a pointer type, then
 141     // THR_OBJ points to the thrown object. If THR_TYPE is a pointer
 142     // type, then THR_OBJ is the pointer itself. OUTER indicates the
 143     // number of outer pointers, and whether they were const
 144     // qualified.
 145     virtual bool __do_catch(const type_info *__thr_type, void **__thr_obj,
 146                             unsigned __outer) const;
 147
 148     // Internally used during catch matching
 149     virtual bool __do_upcast(const __cxxabiv1::__class_type_info *__target,
 150                              void **__obj_ptr) const;
 151
 152   protected:
 153     const char *__name;
 154
 155     explicit type_info(const char *__n): __name(__n) { }
 156
 157   private:
 158     /// Assigning type_info is not supported.
 159     type_info& operator=(const type_info&);
 160     type_info(const type_info&);
 161   };
 162
 163   /**
 164    *  @brief  Thrown during incorrect typecasting.
 165    *  @ingroup exceptions
 166    *
 167    *  If you attempt an invalid @c dynamic_cast expression, an instance of
 168    *  this class (or something derived from this class) is thrown.  */
 169   class bad_cast : public exception
 170   {
 171   public:
 172     bad_cast() throw() { }
 173
 174     // This declaration is not useless:
 175     // http://gcc.gnu.org/onlinedocs/gcc-3.0.2/gcc_6.html#SEC118
 176     virtual ~bad_cast() throw();
 177
 178     // See comment in eh_exception.cc.
 179     virtual const char* what() const throw();
 180   };
 181
 182   /**
 183    *  @brief Thrown when a NULL pointer in a @c typeid expression is used.
 184    *  @ingroup exceptions
 185    */
 186   class bad_typeid : public exception
 187   {
 188   public:
 189     bad_typeid () throw() { }
 190
 191     // This declaration is not useless:
 192     // http://gcc.gnu.org/onlinedocs/gcc-3.0.2/gcc_6.html#SEC118
 193     virtual ~bad_typeid() throw();
 194
 195     // See comment in eh_exception.cc.
 196     virtual const char* what() const throw();
 197   };
 198 } // namespace std
 199
 200 #pragma GCC visibility pop
 201
 202 } // extern "C++"
 203 #endif