1// RTTI support for -*- C++ -*-
2// Copyright (C) 1994-2021 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#pragma GCC visibility push(default)
40
41extern "C++" {
42
43namespace __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
80namespace 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
137#if __cpp_impl_three_way_comparison < 201907L
138 bool operator!=(const type_info& __arg) const _GLIBCXX_NOEXCEPT
139 { return !operator==(__arg); }
140#endif
141
142#if __cplusplus >= 201103L
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 // C++11
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() _GLIBCXX_USE_NOEXCEPT { }
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() _GLIBCXX_USE_NOEXCEPT;
198
199 // See comment in eh_exception.cc.
200 virtual const char* what() const _GLIBCXX_USE_NOEXCEPT;
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 () _GLIBCXX_USE_NOEXCEPT { }
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() _GLIBCXX_USE_NOEXCEPT;
215
216 // See comment in eh_exception.cc.
217 virtual const char* what() const _GLIBCXX_USE_NOEXCEPT;
218 };
219} // namespace std
220
221} // extern "C++"
222
223#pragma GCC visibility pop
224
225#endif
226