1 // Allocators -*- C++ -*-
2
3 // Copyright (C) 2001-2023 Free Software Foundation, Inc.
4 //
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
9 // any later version.
10
11 // This library 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 /*
26 * Copyright (c) 1996-1997
27 * Silicon Graphics Computer Systems, Inc.
28 *
29 * Permission to use, copy, modify, distribute and sell this software
30 * and its documentation for any purpose is hereby granted without fee,
31 * provided that the above copyright notice appear in all copies and
32 * that both that copyright notice and this permission notice appear
33 * in supporting documentation. Silicon Graphics makes no
34 * representations about the suitability of this software for any
35 * purpose. It is provided "as is" without express or implied warranty.
36 */
37
38 /** @file bits/allocator.h
39 * This is an internal header file, included by other library headers.
40 * Do not attempt to use it directly. @headername{memory}
41 */
42
43 #ifndef _ALLOCATOR_H
44 #define _ALLOCATOR_H 1
45
46 #include <bits/c++allocator.h> // Define the base class to std::allocator.
47 #include <bits/memoryfwd.h>
48 #if __cplusplus >= 201103L
49 #include <type_traits>
50 #endif
51
52 #define __cpp_lib_incomplete_container_elements 201505L
53
54 namespace std _GLIBCXX_VISIBILITY(default)
55 {
56 _GLIBCXX_BEGIN_NAMESPACE_VERSION
57
58 /**
59 * @addtogroup allocators
60 * @{
61 */
62
63 // Since C++20 the primary template should be used for allocator<void>,
64 // but then it would have a non-trivial default ctor and dtor for C++20,
65 // but trivial for C++98-17, which would be an ABI incompatibility between
66 // different standard dialects. So C++20 still uses the allocator<void>
67 // explicit specialization, with the historical ABI properties, but with
68 // the same members that are present in the primary template.
69
70 /** std::allocator<void> specialization.
71 *
72 * @headerfile memory
73 */
74 template<>
75 class allocator<void>
76 {
77 public:
78 typedef void value_type;
79 typedef size_t size_type;
80 typedef ptrdiff_t difference_type;
81
82 #if __cplusplus <= 201703L
83 // These were removed for C++20, allocator_traits does the right thing.
84 typedef void* pointer;
85 typedef const void* const_pointer;
86
87 template<typename _Tp1>
88 struct rebind
89 { typedef allocator<_Tp1> other; };
90 #endif
91
92 #if __cplusplus >= 201103L
93 // _GLIBCXX_RESOLVE_LIB_DEFECTS
94 // 2103. std::allocator propagate_on_container_move_assignment
95 using propagate_on_container_move_assignment = true_type;
96
97 using is_always_equal
98 _GLIBCXX20_DEPRECATED_SUGGEST("std::allocator_traits::is_always_equal")
99 = true_type;
100
101 #if __cplusplus >= 202002L
102 // As noted above, these members are present for C++20 to provide the
103 // same API as the primary template, but still trivial as in pre-C++20.
104 allocator() = default;
105 ~allocator() = default;
106
107 template<typename _Up>
108 __attribute__((__always_inline__))
109 constexpr
110 allocator(const allocator<_Up>&) noexcept { }
111
112 // No allocate member because it's ill-formed by LWG 3307.
113 // No deallocate member because it would be undefined to call it
114 // with any pointer which wasn't obtained from allocate.
115 #endif // C++20
116 #endif // C++11
117 };
118
119 /**
120 * @brief The @a standard allocator, as per C++03 [20.4.1].
121 *
122 * See https://gcc.gnu.org/onlinedocs/libstdc++/manual/memory.html#std.util.memory.allocator
123 * for further details.
124 *
125 * @tparam _Tp Type of allocated object.
126 *
127 * @headerfile memory
128 */
129 template<typename _Tp>
130 class allocator : public __allocator_base<_Tp>
131 {
132 public:
133 typedef _Tp value_type;
134 typedef size_t size_type;
135 typedef ptrdiff_t difference_type;
136
137 #if __cplusplus <= 201703L
138 // These were removed for C++20.
139 typedef _Tp* pointer;
140 typedef const _Tp* const_pointer;
141 typedef _Tp& reference;
142 typedef const _Tp& const_reference;
143
144 template<typename _Tp1>
145 struct rebind
146 { typedef allocator<_Tp1> other; };
147 #endif
148
149 #if __cplusplus >= 201103L
150 // _GLIBCXX_RESOLVE_LIB_DEFECTS
151 // 2103. std::allocator propagate_on_container_move_assignment
152 using propagate_on_container_move_assignment = true_type;
153
154 using is_always_equal
155 _GLIBCXX20_DEPRECATED_SUGGEST("std::allocator_traits::is_always_equal")
156 = true_type;
157 #endif
158
159 // _GLIBCXX_RESOLVE_LIB_DEFECTS
160 // 3035. std::allocator's constructors should be constexpr
161 __attribute__((__always_inline__))
162 _GLIBCXX20_CONSTEXPR
163 allocator() _GLIBCXX_NOTHROW { }
164
165 __attribute__((__always_inline__))
166 _GLIBCXX20_CONSTEXPR
167 allocator(const allocator& __a) _GLIBCXX_NOTHROW
168 : __allocator_base<_Tp>(__a) { }
169
170 #if __cplusplus >= 201103L
171 // Avoid implicit deprecation.
172 allocator& operator=(const allocator&) = default;
173 #endif
174
175 template<typename _Tp1>
176 __attribute__((__always_inline__))
177 _GLIBCXX20_CONSTEXPR
178 allocator(const allocator<_Tp1>&) _GLIBCXX_NOTHROW { }
179
180 __attribute__((__always_inline__))
181 #if __cpp_constexpr_dynamic_alloc
182 constexpr
183 #endif
184 ~allocator() _GLIBCXX_NOTHROW { }
185
186 #if __cplusplus > 201703L
187 [[nodiscard,__gnu__::__always_inline__]]
188 constexpr _Tp*
189 allocate(size_t __n)
190 {
191 if (std::__is_constant_evaluated())
192 {
193 if (__builtin_mul_overflow(__n, sizeof(_Tp), &__n))
194 std::__throw_bad_array_new_length();
195 return static_cast<_Tp*>(::operator new(__n));
196 }
197
198 return __allocator_base<_Tp>::allocate(__n, 0);
199 }
200
201 [[__gnu__::__always_inline__]]
202 constexpr void
203 deallocate(_Tp* __p, size_t __n)
204 {
205 if (std::__is_constant_evaluated())
206 {
207 ::operator delete(__p);
208 return;
209 }
210 __allocator_base<_Tp>::deallocate(__p, __n);
211 }
212 #endif // C++20
213
214 friend __attribute__((__always_inline__)) _GLIBCXX20_CONSTEXPR
215 bool
216 operator==(const allocator&, const allocator&) _GLIBCXX_NOTHROW
217 { return true; }
218
219 #if __cpp_impl_three_way_comparison < 201907L
220 friend __attribute__((__always_inline__)) _GLIBCXX20_CONSTEXPR
221 bool
222 operator!=(const allocator&, const allocator&) _GLIBCXX_NOTHROW
223 { return false; }
224 #endif
225
226 // Inherit everything else.
227 };
228
229 /** Equality comparison for std::allocator objects
230 *
231 * @return true, for all std::allocator objects.
232 * @relates std::allocator
233 */
234 template<typename _T1, typename _T2>
235 __attribute__((__always_inline__))
236 inline _GLIBCXX20_CONSTEXPR bool
237 operator==(const allocator<_T1>&, const allocator<_T2>&)
238 _GLIBCXX_NOTHROW
239 { return true; }
240
241 #if __cpp_impl_three_way_comparison < 201907L
242 template<typename _T1, typename _T2>
243 __attribute__((__always_inline__))
244 inline _GLIBCXX20_CONSTEXPR bool
245 operator!=(const allocator<_T1>&, const allocator<_T2>&)
246 _GLIBCXX_NOTHROW
247 { return false; }
248 #endif
249
250 /// @cond undocumented
251
252 // Invalid allocator<cv T> partial specializations.
253 // allocator_traits::rebind_alloc can be used to form a valid allocator type.
254 template<typename _Tp>
255 class allocator<const _Tp>
256 {
257 public:
258 typedef _Tp value_type;
259 template<typename _Up> allocator(const allocator<_Up>&) { }
260 };
261
262 template<typename _Tp>
263 class allocator<volatile _Tp>
264 {
265 public:
266 typedef _Tp value_type;
267 template<typename _Up> allocator(const allocator<_Up>&) { }
268 };
269
270 template<typename _Tp>
271 class allocator<const volatile _Tp>
272 {
273 public:
274 typedef _Tp value_type;
275 template<typename _Up> allocator(const allocator<_Up>&) { }
276 };
277 /// @endcond
278
279 /// @} group allocator
280
281 // Inhibit implicit instantiations for required instantiations,
282 // which are defined via explicit instantiations elsewhere.
283 #if _GLIBCXX_EXTERN_TEMPLATE
284 extern template class allocator<char>;
285 extern template class allocator<wchar_t>;
286 #endif
287
288 // Undefine.
289 #undef __allocator_base
290
291 _GLIBCXX_END_NAMESPACE_VERSION
292 } // namespace std
293
294 #endif