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