1 | // Allocators -*- C++ -*- |
2 | |
3 | // Copyright (C) 2001-2021 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 201505 |
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 incompatibiliy 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 | /// allocator<void> specialization. |
71 | template<> |
72 | class allocator<void> |
73 | { |
74 | public: |
75 | typedef void value_type; |
76 | typedef size_t size_type; |
77 | typedef ptrdiff_t difference_type; |
78 | |
79 | #if __cplusplus <= 201703L |
80 | // These were removed for C++20, allocator_traits does the right thing. |
81 | typedef void* pointer; |
82 | typedef const void* const_pointer; |
83 | |
84 | template<typename _Tp1> |
85 | struct rebind |
86 | { typedef allocator<_Tp1> other; }; |
87 | #endif |
88 | |
89 | #if __cplusplus >= 201103L |
90 | // _GLIBCXX_RESOLVE_LIB_DEFECTS |
91 | // 2103. std::allocator propagate_on_container_move_assignment |
92 | using propagate_on_container_move_assignment = true_type; |
93 | |
94 | using is_always_equal |
95 | _GLIBCXX20_DEPRECATED_SUGGEST("std::allocator_traits::is_always_equal" ) |
96 | = true_type; |
97 | |
98 | #if __cplusplus >= 202002L |
99 | // As noted above, these members are present for C++20 to provide the |
100 | // same API as the primary template, but still trivial as in pre-C++20. |
101 | allocator() = default; |
102 | ~allocator() = default; |
103 | |
104 | template<typename _Up> |
105 | constexpr |
106 | allocator(const allocator<_Up>&) noexcept { } |
107 | |
108 | // No allocate member because it's ill-formed by LWG 3307. |
109 | // No deallocate member because it would be undefined to call it |
110 | // with any pointer which wasn't obtained from allocate. |
111 | #endif // C++20 |
112 | #endif // C++11 |
113 | }; |
114 | |
115 | /** |
116 | * @brief The @a standard allocator, as per C++03 [20.4.1]. |
117 | * |
118 | * See https://gcc.gnu.org/onlinedocs/libstdc++/manual/memory.html#std.util.memory.allocator |
119 | * for further details. |
120 | * |
121 | * @tparam _Tp Type of allocated object. |
122 | */ |
123 | template<typename _Tp> |
124 | class allocator : public __allocator_base<_Tp> |
125 | { |
126 | public: |
127 | typedef _Tp value_type; |
128 | typedef size_t size_type; |
129 | typedef ptrdiff_t difference_type; |
130 | |
131 | #if __cplusplus <= 201703L |
132 | // These were removed for C++20. |
133 | typedef _Tp* pointer; |
134 | typedef const _Tp* const_pointer; |
135 | typedef _Tp& reference; |
136 | typedef const _Tp& const_reference; |
137 | |
138 | template<typename _Tp1> |
139 | struct rebind |
140 | { typedef allocator<_Tp1> other; }; |
141 | #endif |
142 | |
143 | #if __cplusplus >= 201103L |
144 | // _GLIBCXX_RESOLVE_LIB_DEFECTS |
145 | // 2103. std::allocator propagate_on_container_move_assignment |
146 | using propagate_on_container_move_assignment = true_type; |
147 | |
148 | using is_always_equal |
149 | _GLIBCXX20_DEPRECATED_SUGGEST("std::allocator_traits::is_always_equal" ) |
150 | = true_type; |
151 | #endif |
152 | |
153 | // _GLIBCXX_RESOLVE_LIB_DEFECTS |
154 | // 3035. std::allocator's constructors should be constexpr |
155 | _GLIBCXX20_CONSTEXPR |
156 | allocator() _GLIBCXX_NOTHROW { } |
157 | |
158 | _GLIBCXX20_CONSTEXPR |
159 | allocator(const allocator& __a) _GLIBCXX_NOTHROW |
160 | : __allocator_base<_Tp>(__a) { } |
161 | |
162 | #if __cplusplus >= 201103L |
163 | // Avoid implicit deprecation. |
164 | allocator& operator=(const allocator&) = default; |
165 | #endif |
166 | |
167 | template<typename _Tp1> |
168 | _GLIBCXX20_CONSTEXPR |
169 | allocator(const allocator<_Tp1>&) _GLIBCXX_NOTHROW { } |
170 | |
171 | #if __cpp_constexpr_dynamic_alloc |
172 | constexpr |
173 | #endif |
174 | ~allocator() _GLIBCXX_NOTHROW { } |
175 | |
176 | #if __cplusplus > 201703L |
177 | [[nodiscard,__gnu__::__always_inline__]] |
178 | constexpr _Tp* |
179 | allocate(size_t __n) |
180 | { |
181 | #ifdef __cpp_lib_is_constant_evaluated |
182 | if (std::is_constant_evaluated()) |
183 | return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp))); |
184 | #endif |
185 | return __allocator_base<_Tp>::allocate(__n, 0); |
186 | } |
187 | |
188 | [[__gnu__::__always_inline__]] |
189 | constexpr void |
190 | deallocate(_Tp* __p, size_t __n) |
191 | { |
192 | #ifdef __cpp_lib_is_constant_evaluated |
193 | if (std::is_constant_evaluated()) |
194 | { |
195 | ::operator delete(__p); |
196 | return; |
197 | } |
198 | #endif |
199 | __allocator_base<_Tp>::deallocate(__p, __n); |
200 | } |
201 | #endif // C++20 |
202 | |
203 | friend _GLIBCXX20_CONSTEXPR bool |
204 | operator==(const allocator&, const allocator&) _GLIBCXX_NOTHROW |
205 | { return true; } |
206 | |
207 | #if __cpp_impl_three_way_comparison < 201907L |
208 | friend _GLIBCXX20_CONSTEXPR bool |
209 | operator!=(const allocator&, const allocator&) _GLIBCXX_NOTHROW |
210 | { return false; } |
211 | #endif |
212 | |
213 | // Inherit everything else. |
214 | }; |
215 | |
216 | template<typename _T1, typename _T2> |
217 | inline _GLIBCXX20_CONSTEXPR bool |
218 | operator==(const allocator<_T1>&, const allocator<_T2>&) |
219 | _GLIBCXX_NOTHROW |
220 | { return true; } |
221 | |
222 | #if __cpp_impl_three_way_comparison < 201907L |
223 | template<typename _T1, typename _T2> |
224 | inline _GLIBCXX20_CONSTEXPR bool |
225 | operator!=(const allocator<_T1>&, const allocator<_T2>&) |
226 | _GLIBCXX_NOTHROW |
227 | { return false; } |
228 | #endif |
229 | |
230 | // Invalid allocator<cv T> partial specializations. |
231 | // allocator_traits::rebind_alloc can be used to form a valid allocator type. |
232 | template<typename _Tp> |
233 | class allocator<const _Tp> |
234 | { |
235 | public: |
236 | typedef _Tp value_type; |
237 | template<typename _Up> allocator(const allocator<_Up>&) { } |
238 | }; |
239 | |
240 | template<typename _Tp> |
241 | class allocator<volatile _Tp> |
242 | { |
243 | public: |
244 | typedef _Tp value_type; |
245 | template<typename _Up> allocator(const allocator<_Up>&) { } |
246 | }; |
247 | |
248 | template<typename _Tp> |
249 | class allocator<const volatile _Tp> |
250 | { |
251 | public: |
252 | typedef _Tp value_type; |
253 | template<typename _Up> allocator(const allocator<_Up>&) { } |
254 | }; |
255 | |
256 | /// @} group allocator |
257 | |
258 | // Inhibit implicit instantiations for required instantiations, |
259 | // which are defined via explicit instantiations elsewhere. |
260 | #if _GLIBCXX_EXTERN_TEMPLATE |
261 | extern template class allocator<char>; |
262 | extern template class allocator<wchar_t>; |
263 | #endif |
264 | |
265 | // Undefine. |
266 | #undef __allocator_base |
267 | |
268 | // To implement Option 3 of DR 431. |
269 | template<typename _Alloc, bool = __is_empty(_Alloc)> |
270 | struct __alloc_swap |
271 | { static void _S_do_it(_Alloc&, _Alloc&) _GLIBCXX_NOEXCEPT { } }; |
272 | |
273 | template<typename _Alloc> |
274 | struct __alloc_swap<_Alloc, false> |
275 | { |
276 | static void |
277 | _S_do_it(_Alloc& __one, _Alloc& __two) _GLIBCXX_NOEXCEPT |
278 | { |
279 | // Precondition: swappable allocators. |
280 | if (__one != __two) |
281 | swap(__one, __two); |
282 | } |
283 | }; |
284 | |
285 | // Optimize for stateless allocators. |
286 | template<typename _Alloc, bool = __is_empty(_Alloc)> |
287 | struct __alloc_neq |
288 | { |
289 | static bool |
290 | _S_do_it(const _Alloc&, const _Alloc&) |
291 | { return false; } |
292 | }; |
293 | |
294 | template<typename _Alloc> |
295 | struct __alloc_neq<_Alloc, false> |
296 | { |
297 | static bool |
298 | _S_do_it(const _Alloc& __one, const _Alloc& __two) |
299 | { return __one != __two; } |
300 | }; |
301 | |
302 | #if __cplusplus >= 201103L |
303 | template<typename _Tp, bool |
304 | = __or_<is_copy_constructible<typename _Tp::value_type>, |
305 | is_nothrow_move_constructible<typename _Tp::value_type>>::value> |
306 | struct __shrink_to_fit_aux |
307 | { static bool _S_do_it(_Tp&) noexcept { return false; } }; |
308 | |
309 | template<typename _Tp> |
310 | struct __shrink_to_fit_aux<_Tp, true> |
311 | { |
312 | static bool |
313 | _S_do_it(_Tp& __c) noexcept |
314 | { |
315 | #if __cpp_exceptions |
316 | try |
317 | { |
318 | _Tp(__make_move_if_noexcept_iterator(__c.begin()), |
319 | __make_move_if_noexcept_iterator(__c.end()), |
320 | __c.get_allocator()).swap(__c); |
321 | return true; |
322 | } |
323 | catch(...) |
324 | { return false; } |
325 | #else |
326 | return false; |
327 | #endif |
328 | } |
329 | }; |
330 | #endif |
331 | |
332 | _GLIBCXX_END_NAMESPACE_VERSION |
333 | } // namespace std |
334 | |
335 | #endif |
336 | |