libstdc++-v3/libsupc++/typeinfo

   1 // RTTI support for -*- C++ -*-
   2 // Copyright (C) 1994-2016 Free Software Foundation, Inc.
   3 //
   4 // This file is part of GCC.
   5 //
   6 // GCC 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 3, or (at your option)
   9 // any later version.
  10 //
  11 // GCC 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 // Under Section 7 of GPL version 3, you are granted additional
  17 // permissions described in the GCC Runtime Library Exception, version
  18 // 3.1, as published by the Free Software Foundation.
  19
  20 // You should have received a copy of the GNU General Public License and
  21 // a copy of the GCC Runtime Library Exception along with this program;
  22 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23 // <http://www.gnu.org/licenses/>.
  24
  25 /** @file typeinfo
  26  *  This is a Standard C++ Library header.
  27  */
  28
  29 #ifndef _TYPEINFO
  30 #define _TYPEINFO
  31
  32 #pragma GCC system_header
  33
  34 #include <exception>
  35 #if __cplusplus >= 201103L
  36 #include <bits/hash_bytes.h>
  37 #endif
  38
  39 #pragma GCC visibility push(default)
  40
  41 extern "C++" {
  42
  43 namespace __cxxabiv1
  44 {
  45   class __class_type_info;
  46 } // namespace __cxxabiv1
  47
  48 // Determine whether typeinfo names for the same type are merged (in which
  49 // case comparison can just compare pointers) or not (in which case strings
  50 // must be compared), and whether comparison is to be implemented inline or
  51 // not.  We used to do inline pointer comparison by default if weak symbols
  52 // are available, but even with weak symbols sometimes names are not merged
  53 // when objects are loaded with RTLD_LOCAL, so now we always use strcmp by
  54 // default.  For ABI compatibility, we do the strcmp inline if weak symbols
  55 // are available, and out-of-line if not.  Out-of-line pointer comparison
  56 // is used where the object files are to be portable to multiple systems,
  57 // some of which may not be able to use pointer comparison, but the
  58 // particular system for which libstdc++ is being built can use pointer
  59 // comparison; in particular for most ARM EABI systems, where the ABI
  60 // specifies out-of-line comparison.  The compiler's target configuration
  61 // can override the defaults by defining __GXX_TYPEINFO_EQUALITY_INLINE to
  62 // 1 or 0 to indicate whether or not comparison is inline, and
  63 // __GXX_MERGED_TYPEINFO_NAMES to 1 or 0 to indicate whether or not pointer
  64 // comparison can be used.
  65
  66 #ifndef __GXX_MERGED_TYPEINFO_NAMES
  67 // By default, typeinfo names are not merged.
  68 #define __GXX_MERGED_TYPEINFO_NAMES 0
  69 #endif
  70
  71 // By default follow the old inline rules to avoid ABI changes.
  72 #ifndef __GXX_TYPEINFO_EQUALITY_INLINE
  73   #if !__GXX_WEAK__
  74     #define __GXX_TYPEINFO_EQUALITY_INLINE 0
  75   #else
  76     #define __GXX_TYPEINFO_EQUALITY_INLINE 1
  77   #endif
  78 #endif
  79
  80 namespace std
  81 {
  82   /**
  83    *  @brief  Part of RTTI.
  84    *
  85    *  The @c type_info class describes type information generated by
  86    *  an implementation.
  87   */
  88   class type_info
  89   {
  90   public:
  91     /** Destructor first. Being the first non-inline virtual function, this
  92      *  controls in which translation unit the vtable is emitted. The
  93      *  compiler makes use of that information to know where to emit
  94      *  the runtime-mandated type_info structures in the new-abi.  */
  95     virtual ~type_info();
  96
  97     /** Returns an @e implementation-defined byte string; this is not
  98      *  portable between compilers!  */
  99     const char* name() const _GLIBCXX_NOEXCEPT
 100     { return __name[0] == '*' ? __name + 1 : __name; }
 101
 102 #if !__GXX_TYPEINFO_EQUALITY_INLINE
 103     // In old abi, or when weak symbols are not supported, there can
 104     // be multiple instances of a type_info object for one
 105     // type. Uniqueness must use the _name value, not object address.
 106     bool before(const type_info& __arg) const _GLIBCXX_NOEXCEPT;
 107     bool operator==(const type_info& __arg) const _GLIBCXX_NOEXCEPT;
 108 #else
 109   #if !__GXX_MERGED_TYPEINFO_NAMES
 110     /** Returns true if @c *this precedes @c __arg in the implementation's
 111      *  collation order.  */
 112     // Even with the new abi, on systems that support dlopen
 113     // we can run into cases where type_info names aren't merged,
 114     // so we still need to do string comparison.
 115     bool before(const type_info& __arg) const _GLIBCXX_NOEXCEPT
 116     { return (__name[0] == '*' && __arg.__name[0] == '*')
 117         ? __name < __arg.__name
 118         : __builtin_strcmp (__name, __arg.__name) < 0; }
 119
 120     bool operator==(const type_info& __arg) const _GLIBCXX_NOEXCEPT
 121     {
 122       return ((__name == __arg.__name)
 123               || (__name[0] != '*' &&
 124                   __builtin_strcmp (__name, __arg.__name) == 0));
 125     }
 126   #else
 127     // On some targets we can rely on type_info's NTBS being unique,
 128     // and therefore address comparisons are sufficient.
 129     bool before(const type_info& __arg) const _GLIBCXX_NOEXCEPT
 130     { return __name < __arg.__name; }
 131
 132     bool operator==(const type_info& __arg) const _GLIBCXX_NOEXCEPT
 133     { return __name == __arg.__name; }
 134   #endif
 135 #endif
 136     bool operator!=(const type_info& __arg) const _GLIBCXX_NOEXCEPT
 137     { return !operator==(__arg); }
 138
 139 #if __cplusplus >= 201103L
 140     size_t hash_code() const noexcept
 141     {
 142 #  if !__GXX_MERGED_TYPEINFO_NAMES
 143       return _Hash_bytes(name(), __builtin_strlen(name()),
 144                          static_cast<size_t>(0xc70f6907UL));
 145 #  else
 146       return reinterpret_cast<size_t>(__name);
 147 #  endif
 148     }
 149 #endif // C++11
 150
 151     // Return true if this is a pointer type of some kind
 152     virtual bool __is_pointer_p() const;
 153
 154     // Return true if this is a function type
 155     virtual bool __is_function_p() const;
 156
 157     // Try and catch a thrown type. Store an adjusted pointer to the
 158     // caught type in THR_OBJ. If THR_TYPE is not a pointer type, then
 159     // THR_OBJ points to the thrown object. If THR_TYPE is a pointer
 160     // type, then THR_OBJ is the pointer itself. OUTER indicates the
 161     // number of outer pointers, and whether they were const
 162     // qualified.
 163     virtual bool __do_catch(const type_info *__thr_type, void **__thr_obj,
 164                             unsigned __outer) const;
 165
 166     // Internally used during catch matching
 167     virtual bool __do_upcast(const __cxxabiv1::__class_type_info *__target,
 168                              void **__obj_ptr) const;
 169
 170   protected:
 171     const char *__name;
 172
 173     explicit type_info(const char *__n): __name(__n) { }
 174
 175   private:
 176     /// Assigning type_info is not supported.
 177     type_info& operator=(const type_info&);
 178     type_info(const type_info&);
 179   };
 180
 181   /**
 182    *  @brief  Thrown during incorrect typecasting.
 183    *  @ingroup exceptions
 184    *
 185    *  If you attempt an invalid @c dynamic_cast expression, an instance of
 186    *  this class (or something derived from this class) is thrown.  */
 187   class bad_cast : public exception
 188   {
 189   public:
 190     bad_cast() _GLIBCXX_USE_NOEXCEPT { }
 191
 192     // This declaration is not useless:
 193     // http://gcc.gnu.org/onlinedocs/gcc-3.0.2/gcc_6.html#SEC118
 194     virtual ~bad_cast() _GLIBCXX_USE_NOEXCEPT;
 195
 196     // See comment in eh_exception.cc.
 197     virtual const char* what() const _GLIBCXX_USE_NOEXCEPT;
 198   };
 199
 200   /**
 201    *  @brief Thrown when a NULL pointer in a @c typeid expression is used.
 202    *  @ingroup exceptions
 203    */
 204   class bad_typeid : public exception
 205   {
 206   public:
 207     bad_typeid () _GLIBCXX_USE_NOEXCEPT { }
 208
 209     // This declaration is not useless:
 210     // http://gcc.gnu.org/onlinedocs/gcc-3.0.2/gcc_6.html#SEC118
 211     virtual ~bad_typeid() _GLIBCXX_USE_NOEXCEPT;
 212
 213     // See comment in eh_exception.cc.
 214     virtual const char* what() const _GLIBCXX_USE_NOEXCEPT;
 215   };
 216 } // namespace std
 217
 218 } // extern "C++"
 219
 220 #pragma GCC visibility pop
 221
 222 #endif