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1 : // Allocators -*- C++ -*-
2 :
3 : // Copyright (C) 2001-2024 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 : namespace std _GLIBCXX_VISIBILITY(default)
53 : {
54 : _GLIBCXX_BEGIN_NAMESPACE_VERSION
55 :
56 : /**
57 : * @addtogroup allocators
58 : * @{
59 : */
60 :
61 : // Since C++20 the primary template should be used for allocator<void>,
62 : // but then it would have a non-trivial default ctor and dtor for C++20,
63 : // but trivial for C++98-17, which would be an ABI incompatibility between
64 : // different standard dialects. So C++20 still uses the allocator<void>
65 : // explicit specialization, with the historical ABI properties, but with
66 : // the same members that are present in the primary template.
67 :
68 : /** std::allocator<void> specialization.
69 : *
70 : * @headerfile memory
71 : */
72 : template<>
73 : class allocator<void>
74 : {
75 : public:
76 : typedef void value_type;
77 : typedef size_t size_type;
78 : typedef ptrdiff_t difference_type;
79 :
80 : #if __cplusplus <= 201703L
81 : // These were removed for C++20, allocator_traits does the right thing.
82 : typedef void* pointer;
83 : typedef const void* const_pointer;
84 :
85 : template<typename _Tp1>
86 : struct rebind
87 : { typedef allocator<_Tp1> other; };
88 : #endif
89 :
90 : #if __cplusplus >= 201103L
91 : // _GLIBCXX_RESOLVE_LIB_DEFECTS
92 : // 2103. std::allocator propagate_on_container_move_assignment
93 : using propagate_on_container_move_assignment = true_type;
94 :
95 : using is_always_equal
96 : _GLIBCXX20_DEPRECATED_SUGGEST("std::allocator_traits::is_always_equal")
97 : = true_type;
98 :
99 : #if __cplusplus >= 202002L
100 : // As noted above, these members are present for C++20 to provide the
101 : // same API as the primary template, but still trivial as in pre-C++20.
102 : allocator() = default;
103 : ~allocator() = default;
104 :
105 : template<typename _Up>
106 : __attribute__((__always_inline__))
107 : constexpr
108 : allocator(const allocator<_Up>&) noexcept { }
109 :
110 : // No allocate member because it's ill-formed by LWG 3307.
111 : // No deallocate member because it would be undefined to call it
112 : // with any pointer which wasn't obtained from allocate.
113 : #endif // C++20
114 : #endif // C++11
115 : };
116 :
117 : /**
118 : * @brief The @a standard allocator, as per C++03 [20.4.1].
119 : *
120 : * See https://gcc.gnu.org/onlinedocs/libstdc++/manual/memory.html#std.util.memory.allocator
121 : * for further details.
122 : *
123 : * @tparam _Tp Type of allocated object.
124 : *
125 : * @headerfile memory
126 : */
127 : template<typename _Tp>
128 : class allocator : public __allocator_base<_Tp>
129 : {
130 : public:
131 : typedef _Tp value_type;
132 : typedef size_t size_type;
133 : typedef ptrdiff_t difference_type;
134 :
135 : #if __cplusplus <= 201703L
136 : // These were removed for C++20.
137 : typedef _Tp* pointer;
138 : typedef const _Tp* const_pointer;
139 : typedef _Tp& reference;
140 : typedef const _Tp& const_reference;
141 :
142 : template<typename _Tp1>
143 : struct rebind
144 : { typedef allocator<_Tp1> other; };
145 : #endif
146 :
147 : #if __cplusplus >= 201103L
148 : // _GLIBCXX_RESOLVE_LIB_DEFECTS
149 : // 2103. std::allocator propagate_on_container_move_assignment
150 : using propagate_on_container_move_assignment = true_type;
151 :
152 : using is_always_equal
153 : _GLIBCXX20_DEPRECATED_SUGGEST("std::allocator_traits::is_always_equal")
154 : = true_type;
155 : #endif
156 :
157 : // _GLIBCXX_RESOLVE_LIB_DEFECTS
158 : // 3035. std::allocator's constructors should be constexpr
159 : __attribute__((__always_inline__))
160 : _GLIBCXX20_CONSTEXPR
161 90 : allocator() _GLIBCXX_NOTHROW { }
162 :
163 : __attribute__((__always_inline__))
164 : _GLIBCXX20_CONSTEXPR
165 : allocator(const allocator& __a) _GLIBCXX_NOTHROW
166 : : __allocator_base<_Tp>(__a) { }
167 :
168 : #if __cplusplus >= 201103L
169 : // Avoid implicit deprecation.
170 : allocator& operator=(const allocator&) = default;
171 : #endif
172 :
173 : template<typename _Tp1>
174 : __attribute__((__always_inline__))
175 : _GLIBCXX20_CONSTEXPR
176 : allocator(const allocator<_Tp1>&) _GLIBCXX_NOTHROW { }
177 :
178 : __attribute__((__always_inline__))
179 : #if __cpp_constexpr_dynamic_alloc
180 : constexpr
181 : #endif
182 90 : ~allocator() _GLIBCXX_NOTHROW { }
183 :
184 : #if __cplusplus > 201703L
185 : [[nodiscard,__gnu__::__always_inline__]]
186 : constexpr _Tp*
187 : allocate(size_t __n)
188 : {
189 : if (std::__is_constant_evaluated())
190 : {
191 : if (__builtin_mul_overflow(__n, sizeof(_Tp), &__n))
192 : std::__throw_bad_array_new_length();
193 : return static_cast<_Tp*>(::operator new(__n));
194 : }
195 :
196 : return __allocator_base<_Tp>::allocate(__n, 0);
197 : }
198 :
199 : [[__gnu__::__always_inline__]]
200 : constexpr void
201 : deallocate(_Tp* __p, size_t __n)
202 : {
203 : if (std::__is_constant_evaluated())
204 : {
205 : ::operator delete(__p);
206 : return;
207 : }
208 : __allocator_base<_Tp>::deallocate(__p, __n);
209 : }
210 : #endif // C++20
211 :
212 : friend __attribute__((__always_inline__)) _GLIBCXX20_CONSTEXPR
213 : bool
214 : operator==(const allocator&, const allocator&) _GLIBCXX_NOTHROW
215 : { return true; }
216 :
217 : #if __cpp_impl_three_way_comparison < 201907L
218 : friend __attribute__((__always_inline__)) _GLIBCXX20_CONSTEXPR
219 : bool
220 : operator!=(const allocator&, const allocator&) _GLIBCXX_NOTHROW
221 : { return false; }
222 : #endif
223 :
224 : // Inherit everything else.
225 : };
226 :
227 : /** Equality comparison for std::allocator objects
228 : *
229 : * @return true, for all std::allocator objects.
230 : * @relates std::allocator
231 : */
232 : template<typename _T1, typename _T2>
233 : __attribute__((__always_inline__))
234 : inline _GLIBCXX20_CONSTEXPR bool
235 : operator==(const allocator<_T1>&, const allocator<_T2>&)
236 : _GLIBCXX_NOTHROW
237 : { return true; }
238 :
239 : #if __cpp_impl_three_way_comparison < 201907L
240 : template<typename _T1, typename _T2>
241 : __attribute__((__always_inline__))
242 : inline _GLIBCXX20_CONSTEXPR bool
243 : operator!=(const allocator<_T1>&, const allocator<_T2>&)
244 : _GLIBCXX_NOTHROW
245 : { return false; }
246 : #endif
247 :
248 : /// @cond undocumented
249 :
250 : // Invalid allocator<cv T> partial specializations.
251 : // allocator_traits::rebind_alloc can be used to form a valid allocator type.
252 : template<typename _Tp>
253 : class allocator<const _Tp>
254 : {
255 : public:
256 : typedef _Tp value_type;
257 : allocator() { }
258 : template<typename _Up> allocator(const allocator<_Up>&) { }
259 : };
260 :
261 : template<typename _Tp>
262 : class allocator<volatile _Tp>
263 : {
264 : public:
265 : typedef _Tp value_type;
266 : allocator() { }
267 : template<typename _Up> allocator(const allocator<_Up>&) { }
268 : };
269 :
270 : template<typename _Tp>
271 : class allocator<const volatile _Tp>
272 : {
273 : public:
274 : typedef _Tp value_type;
275 : allocator() { }
276 : template<typename _Up> allocator(const allocator<_Up>&) { }
277 : };
278 : /// @endcond
279 :
280 : /// @} group allocator
281 :
282 : // Inhibit implicit instantiations for required instantiations,
283 : // which are defined via explicit instantiations elsewhere.
284 : #if _GLIBCXX_EXTERN_TEMPLATE
285 : extern template class allocator<char>;
286 : extern template class allocator<wchar_t>;
287 : #endif
288 :
289 : // Undefine.
290 : #undef __allocator_base
291 :
292 : _GLIBCXX_END_NAMESPACE_VERSION
293 : } // namespace std
294 :
295 : #endif
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