1 // Allocators -*- C++ -*-
2
3 // Copyright (C) 2001-2020 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
_GLIBCXX_VISIBILITY(default)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, which
65 // would be an ABI change. So C++20 still uses the allocator<void> explicit
66 // specialization, with the historical ABI properties, but with the same
67 // members that are present in the primary template.
68
69 #if ! _GLIBCXX_INLINE_VERSION
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.
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 typedef true_type propagate_on_container_move_assignment;
93
94 typedef true_type is_always_equal;
95
96 #if __cplusplus > 201703L
97 allocator() = default;
98
99 template<typename _Up>
100 constexpr
101 allocator(const allocator<_Up>&) noexcept { }
102
103 // No allocate member because it's ill-formed by LWG 3307.
104 // No deallocate member because it would be undefined to call it
105 // with any pointer which wasn't obtained from allocate.
106
107 #else // ! C++20
108 // allocator_traits<allocator<void>> uses construct and destroy.
109 template<typename _Up, typename... _Args>
110 void
111 construct(_Up* __p, _Args&&... __args)
112 noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
113 { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
114
115 template<typename _Up>
116 void
117 destroy(_Up* __p)
118 noexcept(std::is_nothrow_destructible<_Up>::value)
119 { __p->~_Up(); }
120 #endif // C++17
121 #endif // C++11
122 };
123 #endif // ! _GLIBCXX_INLINE_VERSION
124
125 /**
126 * @brief The @a standard allocator, as per C++03 [20.4.1].
127 *
128 * See https://gcc.gnu.org/onlinedocs/libstdc++/manual/memory.html#std.util.memory.allocator
129 * for further details.
130 *
131 * @tparam _Tp Type of allocated object.
132 */
133 template<typename _Tp>
134 class allocator : public __allocator_base<_Tp>
135 {
136 public:
137 typedef _Tp value_type;
138 typedef size_t size_type;
139 typedef ptrdiff_t difference_type;
140
141 #if __cplusplus <= 201703L
142 // These were removed for C++20.
143 typedef _Tp* pointer;
144 typedef const _Tp* const_pointer;
145 typedef _Tp& reference;
146 typedef const _Tp& const_reference;
147
148 template<typename _Tp1>
149 struct rebind
150 { typedef allocator<_Tp1> other; };
151 #endif
152
153 #if __cplusplus >= 201103L
154 // _GLIBCXX_RESOLVE_LIB_DEFECTS
155 // 2103. std::allocator propagate_on_container_move_assignment
156 typedef true_type propagate_on_container_move_assignment;
157
158 typedef true_type is_always_equal;
159 #endif
160
161 // _GLIBCXX_RESOLVE_LIB_DEFECTS
162 // 3035. std::allocator's constructors should be constexpr
163 _GLIBCXX20_CONSTEXPR
164 allocator() _GLIBCXX_NOTHROW { }
165
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 _GLIBCXX20_CONSTEXPR
177 allocator(const allocator<_Tp1>&) _GLIBCXX_NOTHROW { }
178
179 #if __cpp_constexpr_dynamic_alloc
180 constexpr
181 #endif
182 ~allocator() _GLIBCXX_NOTHROW { }
183
184 #if __cplusplus > 201703L
185 [[nodiscard,__gnu__::__always_inline__]]
186 constexpr _Tp*
187 allocate(size_t __n)
188 {
189 #ifdef __cpp_lib_is_constant_evaluated
190 if (std::is_constant_evaluated())
191 return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp)));
192 #endif
193 return __allocator_base<_Tp>::allocate(__n, 0);
194 }
195
196 [[__gnu__::__always_inline__]]
197 constexpr void
198 deallocate(_Tp* __p, size_t __n)
199 {
200 #ifdef __cpp_lib_is_constant_evaluated
201 if (std::is_constant_evaluated())
202 {
203 ::operator delete(__p);
204 return;
205 }
206 #endif
207 __allocator_base<_Tp>::deallocate(__p, __n);
208 }
209 #endif // C++20
210
211 friend _GLIBCXX20_CONSTEXPR bool
212 operator==(const allocator&, const allocator&) _GLIBCXX_NOTHROW
213 { return true; }
214
215 #if __cpp_impl_three_way_comparison < 201907L
216 friend _GLIBCXX20_CONSTEXPR bool
217 operator!=(const allocator&, const allocator&) _GLIBCXX_NOTHROW
218 { return false; }
219 #endif
220
221 // Inherit everything else.
222 };
223
224 template<typename _T1, typename _T2>
225 inline _GLIBCXX20_CONSTEXPR bool
226 operator==(const allocator<_T1>&, const allocator<_T2>&)
227 _GLIBCXX_NOTHROW
228 { return true; }
229
230 #if __cpp_impl_three_way_comparison < 201907L
231 template<typename _T1, typename _T2>
232 inline _GLIBCXX20_CONSTEXPR bool
233 operator!=(const allocator<_T1>&, const allocator<_T2>&)
234 _GLIBCXX_NOTHROW
235 { return false; }
236 #endif
237
238 // Invalid allocator<cv T> partial specializations.
239 // allocator_traits::rebind_alloc can be used to form a valid allocator type.
240 template<typename _Tp>
241 class allocator<const _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<volatile _Tp>
250 {
251 public:
252 typedef _Tp value_type;
253 template<typename _Up> allocator(const allocator<_Up>&) { }
254 };
255
256 template<typename _Tp>
257 class allocator<const volatile _Tp>
258 {
259 public:
260 typedef _Tp value_type;
261 template<typename _Up> allocator(const allocator<_Up>&) { }
262 };
263
264 /// @} group allocator
265
266 // Inhibit implicit instantiations for required instantiations,
267 // which are defined via explicit instantiations elsewhere.
268 #if _GLIBCXX_EXTERN_TEMPLATE
269 extern template class allocator<char>;
270 extern template class allocator<wchar_t>;
271 #endif
272
273 // Undefine.
274 #undef __allocator_base
275
276 // To implement Option 3 of DR 431.
277 template<typename _Alloc, bool = __is_empty(_Alloc)>
278 struct __alloc_swap
279 { static void _S_do_it(_Alloc&, _Alloc&) _GLIBCXX_NOEXCEPT { } };
280
281 template<typename _Alloc>
282 struct __alloc_swap<_Alloc, false>
283 {
284 static void
285 _S_do_it(_Alloc& __one, _Alloc& __two) _GLIBCXX_NOEXCEPT
286 {
287 // Precondition: swappable allocators.
288 if (__one != __two)
289 swap(__one, __two);
290 }
291 };
292
293 // Optimize for stateless allocators.
294 template<typename _Alloc, bool = __is_empty(_Alloc)>
295 struct __alloc_neq
296 {
297 static bool
298 _S_do_it(const _Alloc&, const _Alloc&)
299 { return false; }
300 };
301
302 template<typename _Alloc>
303 struct __alloc_neq<_Alloc, false>
304 {
305 static bool
306 _S_do_it(const _Alloc& __one, const _Alloc& __two)
307 { return __one != __two; }
308 };
309
310 #if __cplusplus >= 201103L
311 template<typename _Tp, bool
312 = __or_<is_copy_constructible<typename _Tp::value_type>,
313 is_nothrow_move_constructible<typename _Tp::value_type>>::value>
314 struct __shrink_to_fit_aux
315 { static bool _S_do_it(_Tp&) noexcept { return false; } };
316
317 template<typename _Tp>
318 struct __shrink_to_fit_aux<_Tp, true>
319 {
320 static bool
321 _S_do_it(_Tp& __c) noexcept
322 {
323 #if __cpp_exceptions
324 try
325 {
326 _Tp(__make_move_if_noexcept_iterator(__c.begin()),
327 __make_move_if_noexcept_iterator(__c.end()),
328 __c.get_allocator()).swap(__c);
329 return true;
330 }
331 catch(...)
332 { return false; }
333 #else
334 return false;
335 #endif
336 }
337 };
338 #endif
339
340 _GLIBCXX_END_NAMESPACE_VERSION
341 } // namespace std
342
343 #endif
344