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, 2010, 2011
   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 #pragma GCC system_header
  35
  36 #include <exception>
  37 #ifdef __GXX_EXPERIMENTAL_CXX0X__
  38 #include <bits/hash_bytes.h>
  39 #endif
  40
  41
  42 #pragma GCC visibility push(default)
  43
  44 extern "C++" {
  45
  46 namespace __cxxabiv1
  47 {
  48   class __class_type_info;
  49 } // namespace __cxxabiv1
  50
  51 // Determine whether typeinfo names for the same type are merged (in which
  52 // case comparison can just compare pointers) or not (in which case strings
  53 // must be compared), and whether comparison is to be implemented inline or
  54 // not.  We used to do inline pointer comparison by default if weak symbols
  55 // are available, but even with weak symbols sometimes names are not merged
  56 // when objects are loaded with RTLD_LOCAL, so now we always use strcmp by
  57 // default.  For ABI compatibility, we do the strcmp inline if weak symbols
  58 // are available, and out-of-line if not.  Out-of-line pointer comparison
  59 // is used where the object files are to be portable to multiple systems,
  60 // some of which may not be able to use pointer comparison, but the
  61 // particular system for which libstdc++ is being built can use pointer
  62 // comparison; in particular for most ARM EABI systems, where the ABI
  63 // specifies out-of-line comparison.  The compiler's target configuration
  64 // can override the defaults by defining __GXX_TYPEINFO_EQUALITY_INLINE to
  65 // 1 or 0 to indicate whether or not comparison is inline, and
  66 // __GXX_MERGED_TYPEINFO_NAMES to 1 or 0 to indicate whether or not pointer
  67 // comparison can be used.
  68
  69 #ifndef __GXX_MERGED_TYPEINFO_NAMES
  70 // By default, typeinfo names are not merged.
  71 #define __GXX_MERGED_TYPEINFO_NAMES 0
  72 #endif
  73
  74 // By default follow the old inline rules to avoid ABI changes.
  75 #ifndef __GXX_TYPEINFO_EQUALITY_INLINE
  76   #if !__GXX_WEAK__
  77     #define __GXX_TYPEINFO_EQUALITY_INLINE 0
  78   #else
  79     #define __GXX_TYPEINFO_EQUALITY_INLINE 1
  80   #endif
  81 #endif
  82
  83 namespace std
  84 {
  85   /**
  86    *  @brief  Part of RTTI.
  87    *
  88    *  The @c type_info class describes type information generated by
  89    *  an implementation.
  90   */
  91   class type_info
  92   {
  93   public:
  94     /** Destructor first. Being the first non-inline virtual function, this
  95      *  controls in which translation unit the vtable is emitted. The
  96      *  compiler makes use of that information to know where to emit
  97      *  the runtime-mandated type_info structures in the new-abi.  */
  98     virtual ~type_info();
  99
 100     /** Returns an @e implementation-defined byte string; this is not
 101      *  portable between compilers!  */
 102     const char* name() const
 103     { return __name[0] == '*' ? __name + 1 : __name; }
 104
 105 #if !__GXX_TYPEINFO_EQUALITY_INLINE
 106     // In old abi, or when weak symbols are not supported, there can
 107     // be multiple instances of a type_info object for one
 108     // type. Uniqueness must use the _name value, not object address.
 109     bool before(const type_info& __arg) const;
 110     bool operator==(const type_info& __arg) const;
 111 #else
 112   #if !__GXX_MERGED_TYPEINFO_NAMES
 113     /** Returns true if @c *this precedes @c __arg in the implementation's
 114      *  collation order.  */
 115     // Even with the new abi, on systems that support dlopen
 116     // we can run into cases where type_info names aren't merged,
 117     // so we still need to do string comparison.
 118     bool before(const type_info& __arg) const
 119     { return (__name[0] == '*' && __arg.__name[0] == '*')
 120         ? __name < __arg.__name
 121         : __builtin_strcmp (__name, __arg.__name) < 0; }
 122
 123     bool operator==(const type_info& __arg) const
 124     {
 125       return ((__name == __arg.__name)
 126               || (__name[0] != '*' &&
 127                   __builtin_strcmp (__name, __arg.__name) == 0));
 128     }
 129   #else
 130     // On some targets we can rely on type_info's NTBS being unique,
 131     // and therefore address comparisons are sufficient.
 132     bool before(const type_info& __arg) const
 133     { return __name < __arg.__name; }
 134
 135     bool operator==(const type_info& __arg) const
 136     { return __name == __arg.__name; }
 137   #endif
 138 #endif
 139     bool operator!=(const type_info& __arg) const
 140     { return !operator==(__arg); }
 141
 142 #ifdef __GXX_EXPERIMENTAL_CXX0X__
 143     size_t hash_code() const noexcept
 144     {
 145 #  if !__GXX_MERGED_TYPEINFO_NAMES
 146       return _Hash_bytes(name(), __builtin_strlen(name()),
 147                          static_cast<size_t>(0xc70f6907UL));
 148 #  else
 149       return reinterpret_cast<size_t>(__name);
 150 #  endif
 151     }
 152 #endif // __GXX_EXPERIMENTAL_CXX0X__
 153
 154     // Return true if this is a pointer type of some kind
 155     virtual bool __is_pointer_p() const;
 156
 157     // Return true if this is a function type
 158     virtual bool __is_function_p() const;
 159
 160     // Try and catch a thrown type. Store an adjusted pointer to the
 161     // caught type in THR_OBJ. If THR_TYPE is not a pointer type, then
 162     // THR_OBJ points to the thrown object. If THR_TYPE is a pointer
 163     // type, then THR_OBJ is the pointer itself. OUTER indicates the
 164     // number of outer pointers, and whether they were const
 165     // qualified.
 166     virtual bool __do_catch(const type_info *__thr_type, void **__thr_obj,
 167                             unsigned __outer) const;
 168
 169     // Internally used during catch matching
 170     virtual bool __do_upcast(const __cxxabiv1::__class_type_info *__target,
 171                              void **__obj_ptr) const;
 172
 173   protected:
 174     const char *__name;
 175
 176     explicit type_info(const char *__n): __name(__n) { }
 177
 178   private:
 179     /// Assigning type_info is not supported.
 180     type_info& operator=(const type_info&);
 181     type_info(const type_info&);
 182   };
 183
 184   /**
 185    *  @brief  Thrown during incorrect typecasting.
 186    *  @ingroup exceptions
 187    *
 188    *  If you attempt an invalid @c dynamic_cast expression, an instance of
 189    *  this class (or something derived from this class) is thrown.  */
 190   class bad_cast : public exception
 191   {
 192   public:
 193     bad_cast() throw() { }
 194
 195     // This declaration is not useless:
 196     // http://gcc.gnu.org/onlinedocs/gcc-3.0.2/gcc_6.html#SEC118
 197     virtual ~bad_cast() throw();
 198
 199     // See comment in eh_exception.cc.
 200     virtual const char* what() const throw();
 201   };
 202
 203   /**
 204    *  @brief Thrown when a NULL pointer in a @c typeid expression is used.
 205    *  @ingroup exceptions
 206    */
 207   class bad_typeid : public exception
 208   {
 209   public:
 210     bad_typeid () throw() { }
 211
 212     // This declaration is not useless:
 213     // http://gcc.gnu.org/onlinedocs/gcc-3.0.2/gcc_6.html#SEC118
 214     virtual ~bad_typeid() throw();
 215
 216     // See comment in eh_exception.cc.
 217     virtual const char* what() const throw();
 218   };
 219 } // namespace std
 220
 221 #pragma GCC visibility pop
 222
 223 } // extern "C++"
 224 #endif