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
_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 >= 202002L
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 private:
109 // This uses construct and destroy in C++11/14/17 modes.
110 friend allocator_traits<allocator<void>>;
111
112 template<typename _Up, typename... _Args>
113 void
114 construct(_Up* __p, _Args&&... __args)
115 noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
116 { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
117
118 template<typename _Up>
119 void
120 destroy(_Up* __p)
121 noexcept(std::is_nothrow_destructible<_Up>::value)
122 { __p->~_Up(); }
123 #endif // C++17
124 #endif // C++11
125
126 };
127 #endif // ! _GLIBCXX_INLINE_VERSION
128
129 /**
130 * @brief The @a standard allocator, as per C++03 [20.4.1].
131 *
132 * See https://gcc.gnu.org/onlinedocs/libstdc++/manual/memory.html#std.util.memory.allocator
133 * for further details.
134 *
135 * @tparam _Tp Type of allocated object.
136 */
137 template<typename _Tp>
138 class allocator : public __allocator_base<_Tp>
139 {
140 public:
141 typedef _Tp value_type;
142 typedef size_t size_type;
143 typedef ptrdiff_t difference_type;
144
145 #if __cplusplus <= 201703L
146 // These were removed for C++20.
147 typedef _Tp* pointer;
148 typedef const _Tp* const_pointer;
149 typedef _Tp& reference;
150 typedef const _Tp& const_reference;
151
152 template<typename _Tp1>
153 struct rebind
154 { typedef allocator<_Tp1> other; };
155 #endif
156
157 #if __cplusplus >= 201103L
158 // _GLIBCXX_RESOLVE_LIB_DEFECTS
159 // 2103. std::allocator propagate_on_container_move_assignment
160 typedef true_type propagate_on_container_move_assignment;
161
162 typedef true_type is_always_equal;
163 #endif
164
165 // _GLIBCXX_RESOLVE_LIB_DEFECTS
166 // 3035. std::allocator's constructors should be constexpr
167 _GLIBCXX20_CONSTEXPR
168 allocator() _GLIBCXX_NOTHROW { }
169
170 _GLIBCXX20_CONSTEXPR
171 allocator(const allocator& __a) _GLIBCXX_NOTHROW
172 : __allocator_base<_Tp>(__a) { }
173
174 #if __cplusplus >= 201103L
175 // Avoid implicit deprecation.
176 allocator& operator=(const allocator&) = default;
177 #endif
178
179 template<typename _Tp1>
180 _GLIBCXX20_CONSTEXPR
181 allocator(const allocator<_Tp1>&) _GLIBCXX_NOTHROW { }
182
183 #if __cpp_constexpr_dynamic_alloc
184 constexpr
185 #endif
186 ~allocator() _GLIBCXX_NOTHROW { }
187
188 #if __cplusplus > 201703L
189 [[nodiscard,__gnu__::__always_inline__]]
190 constexpr _Tp*
191 allocate(size_t __n)
192 {
193 #ifdef __cpp_lib_is_constant_evaluated
194 if (std::is_constant_evaluated())
195 return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp)));
196 #endif
197 return __allocator_base<_Tp>::allocate(__n, 0);
198 }
199
200 [[__gnu__::__always_inline__]]
201 constexpr void
202 deallocate(_Tp* __p, size_t __n)
203 {
204 #ifdef __cpp_lib_is_constant_evaluated
205 if (std::is_constant_evaluated())
206 {
207 ::operator delete(__p);
208 return;
209 }
210 #endif
211 __allocator_base<_Tp>::deallocate(__p, __n);
212 }
213 #endif // C++20
214
215 friend _GLIBCXX20_CONSTEXPR bool
216 operator==(const allocator&, const allocator&) _GLIBCXX_NOTHROW
217 { return true; }
218
219 #if __cpp_impl_three_way_comparison < 201907L
220 friend _GLIBCXX20_CONSTEXPR bool
221 operator!=(const allocator&, const allocator&) _GLIBCXX_NOTHROW
222 { return false; }
223 #endif
224
225 // Inherit everything else.
226 };
227
228 template<typename _T1, typename _T2>
229 inline _GLIBCXX20_CONSTEXPR bool
230 operator==(const allocator<_T1>&, const allocator<_T2>&)
231 _GLIBCXX_NOTHROW
232 { return true; }
233
234 #if __cpp_impl_three_way_comparison < 201907L
235 template<typename _T1, typename _T2>
236 inline _GLIBCXX20_CONSTEXPR bool
237 operator!=(const allocator<_T1>&, const allocator<_T2>&)
238 _GLIBCXX_NOTHROW
239 { return false; }
240 #endif
241
242 // Invalid allocator<cv T> partial specializations.
243 // allocator_traits::rebind_alloc can be used to form a valid allocator type.
244 template<typename _Tp>
245 class allocator<const _Tp>
246 {
247 public:
248 typedef _Tp value_type;
249 template<typename _Up> allocator(const allocator<_Up>&) { }
250 };
251
252 template<typename _Tp>
253 class allocator<volatile _Tp>
254 {
255 public:
256 typedef _Tp value_type;
257 template<typename _Up> allocator(const allocator<_Up>&) { }
258 };
259
260 template<typename _Tp>
261 class allocator<const volatile _Tp>
262 {
263 public:
264 typedef _Tp value_type;
265 template<typename _Up> allocator(const allocator<_Up>&) { }
266 };
267
268 /// @} group allocator
269
270 // Inhibit implicit instantiations for required instantiations,
271 // which are defined via explicit instantiations elsewhere.
272 #if _GLIBCXX_EXTERN_TEMPLATE
273 extern template class allocator<char>;
274 extern template class allocator<wchar_t>;
275 #endif
276
277 // Undefine.
278 #undef __allocator_base
279
280 // To implement Option 3 of DR 431.
281 template<typename _Alloc, bool = __is_empty(_Alloc)>
282 struct __alloc_swap
283 { static void _S_do_it(_Alloc&, _Alloc&) _GLIBCXX_NOEXCEPT { } };
284
285 template<typename _Alloc>
286 struct __alloc_swap<_Alloc, false>
287 {
288 static void
289 _S_do_it(_Alloc& __one, _Alloc& __two) _GLIBCXX_NOEXCEPT
290 {
291 // Precondition: swappable allocators.
292 if (__one != __two)
293 swap(__one, __two);
294 }
295 };
296
297 // Optimize for stateless allocators.
298 template<typename _Alloc, bool = __is_empty(_Alloc)>
299 struct __alloc_neq
300 {
301 static bool
302 _S_do_it(const _Alloc&, const _Alloc&)
303 { return false; }
304 };
305
306 template<typename _Alloc>
307 struct __alloc_neq<_Alloc, false>
308 {
309 static bool
310 _S_do_it(const _Alloc& __one, const _Alloc& __two)
311 { return __one != __two; }
312 };
313
314 #if __cplusplus >= 201103L
315 template<typename _Tp, bool
316 = __or_<is_copy_constructible<typename _Tp::value_type>,
317 is_nothrow_move_constructible<typename _Tp::value_type>>::value>
318 struct __shrink_to_fit_aux
319 { static bool _S_do_it(_Tp&) noexcept { return false; } };
320
321 template<typename _Tp>
322 struct __shrink_to_fit_aux<_Tp, true>
323 {
324 static bool
325 _S_do_it(_Tp& __c) noexcept
326 {
327 #if __cpp_exceptions
328 try
329 {
330 _Tp(__make_move_if_noexcept_iterator(__c.begin()),
331 __make_move_if_noexcept_iterator(__c.end()),
332 __c.get_allocator()).swap(__c);
333 return true;
334 }
335 catch(...)
336 { return false; }
337 #else
338 return false;
339 #endif
340 }
341 };
342 #endif
343
344 _GLIBCXX_END_NAMESPACE_VERSION
345 } // namespace std
346
347 #endif
348