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, 2012
   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 #if __cplusplus >= 201103L
  38 #include <bits/hash_bytes.h>
  39 #endif
  40
  41 #pragma GCC visibility push(default)
  42
  43 extern "C++" {
  44
  45 namespace __cxxabiv1
  46 {
  47   class __class_type_info;
  48 } // namespace __cxxabiv1
  49
  50 // Determine whether typeinfo names for the same type are merged (in which
  51 // case comparison can just compare pointers) or not (in which case strings
  52 // must be compared), and whether comparison is to be implemented inline or
  53 // not.  We used to do inline pointer comparison by default if weak symbols
  54 // are available, but even with weak symbols sometimes names are not merged
  55 // when objects are loaded with RTLD_LOCAL, so now we always use strcmp by
  56 // default.  For ABI compatibility, we do the strcmp inline if weak symbols
  57 // are available, and out-of-line if not.  Out-of-line pointer comparison
  58 // is used where the object files are to be portable to multiple systems,
  59 // some of which may not be able to use pointer comparison, but the
  60 // particular system for which libstdc++ is being built can use pointer
  61 // comparison; in particular for most ARM EABI systems, where the ABI
  62 // specifies out-of-line comparison.  The compiler's target configuration
  63 // can override the defaults by defining __GXX_TYPEINFO_EQUALITY_INLINE to
  64 // 1 or 0 to indicate whether or not comparison is inline, and
  65 // __GXX_MERGED_TYPEINFO_NAMES to 1 or 0 to indicate whether or not pointer
  66 // comparison can be used.
  67
  68 #ifndef __GXX_MERGED_TYPEINFO_NAMES
  69 // By default, typeinfo names are not merged.
  70 #define __GXX_MERGED_TYPEINFO_NAMES 0
  71 #endif
  72
  73 // By default follow the old inline rules to avoid ABI changes.
  74 #ifndef __GXX_TYPEINFO_EQUALITY_INLINE
  75   #if !__GXX_WEAK__
  76     #define __GXX_TYPEINFO_EQUALITY_INLINE 0
  77   #else
  78     #define __GXX_TYPEINFO_EQUALITY_INLINE 1
  79   #endif
  80 #endif
  81
  82 namespace std
  83 {
  84   /**
  85    *  @brief  Part of RTTI.
  86    *
  87    *  The @c type_info class describes type information generated by
  88    *  an implementation.
  89   */
  90   class type_info
  91   {
  92   public:
  93     /** Destructor first. Being the first non-inline virtual function, this
  94      *  controls in which translation unit the vtable is emitted. The
  95      *  compiler makes use of that information to know where to emit
  96      *  the runtime-mandated type_info structures in the new-abi.  */
  97     virtual ~type_info();
  98
  99     /** Returns an @e implementation-defined byte string; this is not
 100      *  portable between compilers!  */
 101     const char* name() const _GLIBCXX_NOEXCEPT
 102     { return __name[0] == '*' ? __name + 1 : __name; }
 103
 104 #if !__GXX_TYPEINFO_EQUALITY_INLINE
 105     // In old abi, or when weak symbols are not supported, there can
 106     // be multiple instances of a type_info object for one
 107     // type. Uniqueness must use the _name value, not object address.
 108     bool before(const type_info& __arg) const _GLIBCXX_NOEXCEPT;
 109     bool operator==(const type_info& __arg) const _GLIBCXX_NOEXCEPT;
 110 #else
 111   #if !__GXX_MERGED_TYPEINFO_NAMES
 112     /** Returns true if @c *this precedes @c __arg in the implementation's
 113      *  collation order.  */
 114     // Even with the new abi, on systems that support dlopen
 115     // we can run into cases where type_info names aren't merged,
 116     // so we still need to do string comparison.
 117     bool before(const type_info& __arg) const _GLIBCXX_NOEXCEPT
 118     { return (__name[0] == '*' && __arg.__name[0] == '*')
 119         ? __name < __arg.__name
 120         : __builtin_strcmp (__name, __arg.__name) < 0; }
 121
 122     bool operator==(const type_info& __arg) const _GLIBCXX_NOEXCEPT
 123     {
 124       return ((__name == __arg.__name)
 125               || (__name[0] != '*' &&
 126                   __builtin_strcmp (__name, __arg.__name) == 0));
 127     }
 128   #else
 129     // On some targets we can rely on type_info's NTBS being unique,
 130     // and therefore address comparisons are sufficient.
 131     bool before(const type_info& __arg) const _GLIBCXX_NOEXCEPT
 132     { return __name < __arg.__name; }
 133
 134     bool operator==(const type_info& __arg) const _GLIBCXX_NOEXCEPT
 135     { return __name == __arg.__name; }
 136   #endif
 137 #endif
 138     bool operator!=(const type_info& __arg) const _GLIBCXX_NOEXCEPT
 139     { return !operator==(__arg); }
 140
 141 #if __cplusplus >= 201103L
 142     size_t hash_code() const noexcept
 143     {
 144 #  if !__GXX_MERGED_TYPEINFO_NAMES
 145       return _Hash_bytes(name(), __builtin_strlen(name()),
 146                          static_cast<size_t>(0xc70f6907UL));
 147 #  else
 148       return reinterpret_cast<size_t>(__name);
 149 #  endif
 150     }
 151 #endif // C++11
 152
 153     // Return true if this is a pointer type of some kind
 154     virtual bool __is_pointer_p() const;
 155
 156     // Return true if this is a function type
 157     virtual bool __is_function_p() const;
 158
 159     // Try and catch a thrown type. Store an adjusted pointer to the
 160     // caught type in THR_OBJ. If THR_TYPE is not a pointer type, then
 161     // THR_OBJ points to the thrown object. If THR_TYPE is a pointer
 162     // type, then THR_OBJ is the pointer itself. OUTER indicates the
 163     // number of outer pointers, and whether they were const
 164     // qualified.
 165     virtual bool __do_catch(const type_info *__thr_type, void **__thr_obj,
 166                             unsigned __outer) const;
 167
 168     // Internally used during catch matching
 169     virtual bool __do_upcast(const __cxxabiv1::__class_type_info *__target,
 170                              void **__obj_ptr) const;
 171
 172   protected:
 173     const char *__name;
 174
 175     explicit type_info(const char *__n): __name(__n) { }
 176
 177   private:
 178     /// Assigning type_info is not supported.
 179     type_info& operator=(const type_info&);
 180     type_info(const type_info&);
 181   };
 182
 183   /**
 184    *  @brief  Thrown during incorrect typecasting.
 185    *  @ingroup exceptions
 186    *
 187    *  If you attempt an invalid @c dynamic_cast expression, an instance of
 188    *  this class (or something derived from this class) is thrown.  */
 189   class bad_cast : public exception
 190   {
 191   public:
 192     bad_cast() _GLIBCXX_USE_NOEXCEPT { }
 193
 194     // This declaration is not useless:
 195     // http://gcc.gnu.org/onlinedocs/gcc-3.0.2/gcc_6.html#SEC118
 196     virtual ~bad_cast() _GLIBCXX_USE_NOEXCEPT;
 197
 198     // See comment in eh_exception.cc.
 199     virtual const char* what() const _GLIBCXX_USE_NOEXCEPT;
 200   };
 201
 202   /**
 203    *  @brief Thrown when a NULL pointer in a @c typeid expression is used.
 204    *  @ingroup exceptions
 205    */
 206   class bad_typeid : public exception
 207   {
 208   public:
 209     bad_typeid () _GLIBCXX_USE_NOEXCEPT { }
 210
 211     // This declaration is not useless:
 212     // http://gcc.gnu.org/onlinedocs/gcc-3.0.2/gcc_6.html#SEC118
 213     virtual ~bad_typeid() _GLIBCXX_USE_NOEXCEPT;
 214
 215     // See comment in eh_exception.cc.
 216     virtual const char* what() const _GLIBCXX_USE_NOEXCEPT;
 217   };
 218 } // namespace std
 219
 220 } // extern "C++"
 221
 222 #pragma GCC visibility pop
 223
 224 #endif