1 // RTTI support for -*- C++ -*-
2 // Copyright (C) 1994-2024 Free Software Foundation, Inc.
4 // This file is part of GCC.
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)
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.
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.
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/>.
26 * This is a Standard C++ Library header.
32 #pragma GCC system_header
34 #include <bits/exception.h>
35 #if __cplusplus >= 201103L
36 #include <bits/hash_bytes.h>
39 #define __glibcxx_want_constexpr_typeinfo
40 #include <bits/version.h>
42 #pragma GCC visibility push(default)
48 class __class_type_info;
49 } // namespace __cxxabiv1
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.
69 #ifndef __GXX_MERGED_TYPEINFO_NAMES
70 // By default, typeinfo names are not merged.
71 #define __GXX_MERGED_TYPEINFO_NAMES 0
74 // By default follow the old inline rules to avoid ABI changes.
75 #ifndef __GXX_TYPEINFO_EQUALITY_INLINE
77 # define __GXX_TYPEINFO_EQUALITY_INLINE 0
79 # define __GXX_TYPEINFO_EQUALITY_INLINE 1
86 * @brief Part of RTTI.
88 * The @c type_info class describes type information generated by
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. */
100 /** Returns an @e implementation-defined byte string; this is not
101 * portable between compilers! */
102 const char* name() const _GLIBCXX_NOEXCEPT
103 { return __name[0] == '*' ? __name + 1 : __name; }
105 /** Returns true if `*this` precedes `__arg` in the implementation's
106 * collation order. */
107 bool before(const type_info& __arg) const _GLIBCXX_NOEXCEPT;
110 bool operator==(const type_info& __arg) const _GLIBCXX_NOEXCEPT;
112 #if __cpp_impl_three_way_comparison < 201907L
113 bool operator!=(const type_info& __arg) const _GLIBCXX_NOEXCEPT
114 { return !operator==(__arg); }
117 #if __cplusplus >= 201103L
118 size_t hash_code() const noexcept
120 # if !__GXX_MERGED_TYPEINFO_NAMES
121 return _Hash_bytes(name(), __builtin_strlen(name()),
122 static_cast<size_t>(0xc70f6907UL));
124 return reinterpret_cast<size_t>(__name);
129 // Return true if this is a pointer type of some kind
130 virtual bool __is_pointer_p() const;
132 // Return true if this is a function type
133 virtual bool __is_function_p() const;
135 // Try and catch a thrown type. Store an adjusted pointer to the
136 // caught type in THR_OBJ. If THR_TYPE is not a pointer type, then
137 // THR_OBJ points to the thrown object. If THR_TYPE is a pointer
138 // type, then THR_OBJ is the pointer itself. OUTER indicates the
139 // number of outer pointers, and whether they were const
141 virtual bool __do_catch(const type_info *__thr_type, void **__thr_obj,
142 unsigned __outer) const;
144 // Internally used during catch matching
145 virtual bool __do_upcast(const __cxxabiv1::__class_type_info *__target,
146 void **__obj_ptr) const;
151 explicit type_info(const char *__n): __name(__n) { }
154 // type_info objects cannot be copied.
155 #if __cplusplus >= 201103L
156 type_info& operator=(const type_info&) = delete;
157 type_info(const type_info&) = delete;
159 type_info& operator=(const type_info&);
160 type_info(const type_info&);
163 #if ! __GXX_TYPEINFO_EQUALITY_INLINE
164 bool __equal(const type_info&) const _GLIBCXX_NOEXCEPT;
168 #if __GXX_TYPEINFO_EQUALITY_INLINE
170 type_info::before(const type_info& __arg) const _GLIBCXX_NOEXCEPT
172 #if !__GXX_MERGED_TYPEINFO_NAMES
173 // Even with the new abi, on systems that support dlopen
174 // we can run into cases where type_info names aren't merged,
175 // so we still need to do string comparison.
176 if (__name[0] != '*' || __arg.__name[0] != '*')
177 return __builtin_strcmp (__name, __arg.__name) < 0;
179 // On some targets we can rely on type_info's NTBS being unique,
180 // and therefore address comparisons are sufficient.
183 // In old abi, or when weak symbols are not supported, there can
184 // be multiple instances of a type_info object for one
185 // type. Uniqueness must use the __name value, not object address.
186 return __name < __arg.__name;
190 #if __GXX_TYPEINFO_EQUALITY_INLINE || __cplusplus > 202002L
191 _GLIBCXX23_CONSTEXPR inline bool
192 type_info::operator==(const type_info& __arg) const _GLIBCXX_NOEXCEPT
194 if (std::__is_constant_evaluated())
195 return this == &__arg;
197 if (__name == __arg.__name)
200 #if !__GXX_TYPEINFO_EQUALITY_INLINE
201 // ABI requires comparisons to be non-inline.
202 return __equal(__arg);
203 #elif !__GXX_MERGED_TYPEINFO_NAMES
204 // Need to do string comparison.
205 return __name[0] != '*' && __builtin_strcmp (__name, __arg.name()) == 0;
214 * @brief Thrown during incorrect typecasting.
215 * @ingroup exceptions
217 * If you attempt an invalid @c dynamic_cast expression, an instance of
218 * this class (or something derived from this class) is thrown. */
219 class bad_cast : public exception
222 bad_cast() _GLIBCXX_USE_NOEXCEPT { }
224 // This declaration is not useless:
225 // http://gcc.gnu.org/onlinedocs/gcc-3.0.2/gcc_6.html#SEC118
226 virtual ~bad_cast() _GLIBCXX_USE_NOEXCEPT;
228 // See comment in eh_exception.cc.
229 virtual const char* what() const _GLIBCXX_USE_NOEXCEPT;
233 * @brief Thrown when a NULL pointer in a @c typeid expression is used.
234 * @ingroup exceptions
236 class bad_typeid : public exception
239 bad_typeid () _GLIBCXX_USE_NOEXCEPT { }
241 // This declaration is not useless:
242 // http://gcc.gnu.org/onlinedocs/gcc-3.0.2/gcc_6.html#SEC118
243 virtual ~bad_typeid() _GLIBCXX_USE_NOEXCEPT;
245 // See comment in eh_exception.cc.
246 virtual const char* what() const _GLIBCXX_USE_NOEXCEPT;
252 #pragma GCC visibility pop