1// RTTI support for -*- C++ -*-
2// Copyright (C) 1994-2024 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 <bits/exception.h>
35#if __cplusplus >= 201103L
36#include <bits/hash_bytes.h>
37#endif
38
39#define __glibcxx_want_constexpr_typeinfo
40#include <bits/version.h>
41
42#pragma GCC visibility push(default)
43
44extern "C++" {
45
46namespace __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
83namespace 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 _GLIBCXX_NOEXCEPT
103 { return __name[0] == '*' ? __name + 1 : __name; }
104
105 /** Returns true if `*this` precedes `__arg` in the implementation's
106 * collation order. */
107 bool before(const type_info& __arg) const _GLIBCXX_NOEXCEPT;
108
109 _GLIBCXX23_CONSTEXPR
110 bool operator==(const type_info& __arg) const _GLIBCXX_NOEXCEPT;
111
112#if __cpp_impl_three_way_comparison < 201907L
113 bool operator!=(const type_info& __arg) const _GLIBCXX_NOEXCEPT
114 { return !operator==(__arg); }
115#endif
116
117#if __cplusplus >= 201103L
118 size_t hash_code() const noexcept
119 {
120# if !__GXX_MERGED_TYPEINFO_NAMES
121 return _Hash_bytes(ptr: name(), len: __builtin_strlen(name()),
122 seed: static_cast<size_t>(0xc70f6907UL));
123# else
124 return reinterpret_cast<size_t>(__name);
125# endif
126 }
127#endif // C++11
128
129 // Return true if this is a pointer type of some kind
130 virtual bool __is_pointer_p() const;
131
132 // Return true if this is a function type
133 virtual bool __is_function_p() const;
134
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
140 // qualified.
141 virtual bool __do_catch(const type_info *__thr_type, void **__thr_obj,
142 unsigned __outer) const;
143
144 // Internally used during catch matching
145 virtual bool __do_upcast(const __cxxabiv1::__class_type_info *__target,
146 void **__obj_ptr) const;
147
148 protected:
149 const char *__name;
150
151 explicit type_info(const char *__n): __name(__n) { }
152
153 private:
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;
158#else
159 type_info& operator=(const type_info&);
160 type_info(const type_info&);
161#endif
162
163#if ! __GXX_TYPEINFO_EQUALITY_INLINE
164 bool __equal(const type_info&) const _GLIBCXX_NOEXCEPT;
165#endif
166 };
167
168#if __GXX_TYPEINFO_EQUALITY_INLINE
169 inline bool
170 type_info::before(const type_info& __arg) const _GLIBCXX_NOEXCEPT
171 {
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;
178#else
179 // On some targets we can rely on type_info's NTBS being unique,
180 // and therefore address comparisons are sufficient.
181#endif
182
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;
187 }
188#endif
189
190#if __GXX_TYPEINFO_EQUALITY_INLINE || __cplusplus > 202002L
191 _GLIBCXX23_CONSTEXPR inline bool
192 type_info::operator==(const type_info& __arg) const _GLIBCXX_NOEXCEPT
193 {
194 if (std::__is_constant_evaluated())
195 return this == &__arg;
196
197 if (__name == __arg.__name)
198 return true;
199
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;
206#else
207 return false;
208#endif
209 }
210# endif
211
212
213 /**
214 * @brief Thrown during incorrect typecasting.
215 * @ingroup exceptions
216 *
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
220 {
221 public:
222 bad_cast() _GLIBCXX_USE_NOEXCEPT { }
223
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;
227
228 // See comment in eh_exception.cc.
229 virtual const char* what() const _GLIBCXX_USE_NOEXCEPT;
230 };
231
232 /**
233 * @brief Thrown when a NULL pointer in a @c typeid expression is used.
234 * @ingroup exceptions
235 */
236 class bad_typeid : public exception
237 {
238 public:
239 bad_typeid () _GLIBCXX_USE_NOEXCEPT { }
240
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;
244
245 // See comment in eh_exception.cc.
246 virtual const char* what() const _GLIBCXX_USE_NOEXCEPT;
247 };
248} // namespace std
249
250} // extern "C++"
251
252#pragma GCC visibility pop
253
254#endif
255