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
54namespace 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 using propagate_on_container_move_assignment = true_type;
93
94 using is_always_equal
95 _GLIBCXX20_DEPRECATED_SUGGEST("allocator_traits::is_always_equal")
96 = true_type;
97
98#if __cplusplus >= 202002L
99 allocator() = default;
100
101 template<typename _Up>
102 constexpr
103 allocator(const allocator<_Up>&) noexcept { }
104
105 // No allocate member because it's ill-formed by LWG 3307.
106 // No deallocate member because it would be undefined to call it
107 // with any pointer which wasn't obtained from allocate.
108
109#else // ! C++20
110 private:
111 // This uses construct and destroy in C++11/14/17 modes.
112 friend allocator_traits<allocator<void>>;
113
114 template<typename _Up, typename... _Args>
115 void
116 construct(_Up* __p, _Args&&... __args)
117 noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
118 { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
119
120 template<typename _Up>
121 void
122 destroy(_Up* __p)
123 noexcept(std::is_nothrow_destructible<_Up>::value)
124 { __p->~_Up(); }
125#endif // C++17
126#endif // C++11
127
128 };
129#endif // ! _GLIBCXX_INLINE_VERSION
130
131 /**
132 * @brief The @a standard allocator, as per C++03 [20.4.1].
133 *
134 * See https://gcc.gnu.org/onlinedocs/libstdc++/manual/memory.html#std.util.memory.allocator
135 * for further details.
136 *
137 * @tparam _Tp Type of allocated object.
138 */
139 template<typename _Tp>
140 class allocator : public __allocator_base<_Tp>
141 {
142 public:
143 typedef _Tp value_type;
144 typedef size_t size_type;
145 typedef ptrdiff_t difference_type;
146
147#if __cplusplus <= 201703L
148 // These were removed for C++20.
149 typedef _Tp* pointer;
150 typedef const _Tp* const_pointer;
151 typedef _Tp& reference;
152 typedef const _Tp& const_reference;
153
154 template<typename _Tp1>
155 struct rebind
156 { typedef allocator<_Tp1> other; };
157#endif
158
159#if __cplusplus >= 201103L
160 // _GLIBCXX_RESOLVE_LIB_DEFECTS
161 // 2103. std::allocator propagate_on_container_move_assignment
162 using propagate_on_container_move_assignment = true_type;
163
164 using is_always_equal
165 _GLIBCXX20_DEPRECATED_SUGGEST("allocator_traits::is_always_equal")
166 = true_type;
167#endif
168
169 // _GLIBCXX_RESOLVE_LIB_DEFECTS
170 // 3035. std::allocator's constructors should be constexpr
171 _GLIBCXX20_CONSTEXPR
172 allocator() _GLIBCXX_NOTHROW { }
173
174 _GLIBCXX20_CONSTEXPR
175 allocator(const allocator& __a) _GLIBCXX_NOTHROW
176 : __allocator_base<_Tp>(__a) { }
177
178#if __cplusplus >= 201103L
179 // Avoid implicit deprecation.
180 allocator& operator=(const allocator&) = default;
181#endif
182
183 template<typename _Tp1>
184 _GLIBCXX20_CONSTEXPR
185 allocator(const allocator<_Tp1>&) _GLIBCXX_NOTHROW { }
186
187#if __cpp_constexpr_dynamic_alloc
188 constexpr
189#endif
190 ~allocator() _GLIBCXX_NOTHROW { }
191
192#if __cplusplus > 201703L
193 [[nodiscard,__gnu__::__always_inline__]]
194 constexpr _Tp*
195 allocate(size_t __n)
196 {
197#ifdef __cpp_lib_is_constant_evaluated
198 if (std::is_constant_evaluated())
199 return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp)));
200#endif
201 return __allocator_base<_Tp>::allocate(__n, 0);
202 }
203
204 [[__gnu__::__always_inline__]]
205 constexpr void
206 deallocate(_Tp* __p, size_t __n)
207 {
208#ifdef __cpp_lib_is_constant_evaluated
209 if (std::is_constant_evaluated())
210 {
211 ::operator delete(__p);
212 return;
213 }
214#endif
215 __allocator_base<_Tp>::deallocate(__p, __n);
216 }
217#endif // C++20
218
219 friend _GLIBCXX20_CONSTEXPR bool
220 operator==(const allocator&, const allocator&) _GLIBCXX_NOTHROW
221 { return true; }
222
223#if __cpp_impl_three_way_comparison < 201907L
224 friend _GLIBCXX20_CONSTEXPR bool
225 operator!=(const allocator&, const allocator&) _GLIBCXX_NOTHROW
226 { return false; }
227#endif
228
229 // Inherit everything else.
230 };
231
232 template<typename _T1, typename _T2>
233 inline _GLIBCXX20_CONSTEXPR bool
234 operator==(const allocator<_T1>&, const allocator<_T2>&)
235 _GLIBCXX_NOTHROW
236 { return true; }
237
238#if __cpp_impl_three_way_comparison < 201907L
239 template<typename _T1, typename _T2>
240 inline _GLIBCXX20_CONSTEXPR bool
241 operator!=(const allocator<_T1>&, const allocator<_T2>&)
242 _GLIBCXX_NOTHROW
243 { return false; }
244#endif
245
246 // Invalid allocator<cv T> partial specializations.
247 // allocator_traits::rebind_alloc can be used to form a valid allocator type.
248 template<typename _Tp>
249 class allocator<const _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<volatile _Tp>
258 {
259 public:
260 typedef _Tp value_type;
261 template<typename _Up> allocator(const allocator<_Up>&) { }
262 };
263
264 template<typename _Tp>
265 class allocator<const volatile _Tp>
266 {
267 public:
268 typedef _Tp value_type;
269 template<typename _Up> allocator(const allocator<_Up>&) { }
270 };
271
272 /// @} group allocator
273
274 // Inhibit implicit instantiations for required instantiations,
275 // which are defined via explicit instantiations elsewhere.
276#if _GLIBCXX_EXTERN_TEMPLATE
277 extern template class allocator<char>;
278 extern template class allocator<wchar_t>;
279#endif
280
281 // Undefine.
282#undef __allocator_base
283
284 // To implement Option 3 of DR 431.
285 template<typename _Alloc, bool = __is_empty(_Alloc)>
286 struct __alloc_swap
287 { static void _S_do_it(_Alloc&, _Alloc&) _GLIBCXX_NOEXCEPT { } };
288
289 template<typename _Alloc>
290 struct __alloc_swap<_Alloc, false>
291 {
292 static void
293 _S_do_it(_Alloc& __one, _Alloc& __two) _GLIBCXX_NOEXCEPT
294 {
295 // Precondition: swappable allocators.
296 if (__one != __two)
297 swap(__one, __two);
298 }
299 };
300
301 // Optimize for stateless allocators.
302 template<typename _Alloc, bool = __is_empty(_Alloc)>
303 struct __alloc_neq
304 {
305 static bool
306 _S_do_it(const _Alloc&, const _Alloc&)
307 { return false; }
308 };
309
310 template<typename _Alloc>
311 struct __alloc_neq<_Alloc, false>
312 {
313 static bool
314 _S_do_it(const _Alloc& __one, const _Alloc& __two)
315 { return __one != __two; }
316 };
317
318#if __cplusplus >= 201103L
319 template<typename _Tp, bool
320 = __or_<is_copy_constructible<typename _Tp::value_type>,
321 is_nothrow_move_constructible<typename _Tp::value_type>>::value>
322 struct __shrink_to_fit_aux
323 { static bool _S_do_it(_Tp&) noexcept { return false; } };
324
325 template<typename _Tp>
326 struct __shrink_to_fit_aux<_Tp, true>
327 {
328 static bool
329 _S_do_it(_Tp& __c) noexcept
330 {
331#if __cpp_exceptions
332 try
333 {
334 _Tp(__make_move_if_noexcept_iterator(__c.begin()),
335 __make_move_if_noexcept_iterator(__c.end()),
336 __c.get_allocator()).swap(__c);
337 return true;
338 }
339 catch(...)
340 { return false; }
341#else
342 return false;
343#endif
344 }
345 };
346#endif
347
348_GLIBCXX_END_NAMESPACE_VERSION
349} // namespace std
350
351#endif
352