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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 1078750 : allocator() _GLIBCXX_NOTHROW { }
157 :
158 : _GLIBCXX20_CONSTEXPR
159 1789460 : allocator(const allocator& __a) _GLIBCXX_NOTHROW
160 1789460 : : __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 1349891 : allocator(const allocator<_Tp1>&) _GLIBCXX_NOTHROW { }
170 :
171 : #if __cpp_constexpr_dynamic_alloc
172 : constexpr
173 : #endif
174 8381209 : ~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 0 : operator!=(const allocator&, const allocator&) _GLIBCXX_NOTHROW
210 0 : { return false; }
211 : #endif
212 :
213 : // Inherit everything else.
214 : };
215 :
216 : template<typename _T1, typename _T2>
217 : inline _GLIBCXX20_CONSTEXPR bool
218 14 : operator==(const allocator<_T1>&, const allocator<_T2>&)
219 : _GLIBCXX_NOTHROW
220 14 : { 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 87 : _S_do_it(const _Alloc&, const _Alloc&)
291 87 : { 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 0 : _S_do_it(_Tp& __c) noexcept
314 : {
315 : #if __cpp_exceptions
316 : try
317 : {
318 0 : _Tp(__make_move_if_noexcept_iterator(__c.begin()),
319 : __make_move_if_noexcept_iterator(__c.end()),
320 0 : __c.get_allocator()).swap(__c);
321 0 : return true;
322 : }
323 0 : catch(...)
324 0 : { 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
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