libstdc++

typeinfo
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1 // RTTI support for -*- C++ -*-
2 // Copyright (C) 1994-2013 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