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 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 using propagate_on_container_move_assignment = true_type; 
93 
94 using is_always_equal 
95 _GLIBCXX20_DEPRECATED_SUGGEST("std::allocator_traits::is_always_equal") 
96 = true_type; 
97 
98#if __cplusplus >= 202002L 
99 // As noted above, these members are present for C++20 to provide the 
100 // same API as the primary template, but still trivial as in pre-C++20. 
101 allocator() = default; 
102 ~allocator() = default; 
103 
104 template<typename _Up> 
105 constexpr 
106 allocator(const allocator<_Up>&) noexcept { } 
107 
108 // No allocate member because it's ill-formed by LWG 3307. 
109 // No deallocate member because it would be undefined to call it 
110 // with any pointer which wasn't obtained from allocate. 
111#endif // C++20 
112#endif // C++11 
113 }; 
114 
115 /** 
116 * @brief The @a standard allocator, as per C++03 [20.4.1]. 
117 * 
118 * See https://gcc.gnu.org/onlinedocs/libstdc++/manual/memory.html#std.util.memory.allocator 
119 * for further details. 
120 * 
121 * @tparam _Tp Type of allocated object. 
122 */ 
123 template<typename _Tp> 
124 class allocator : public __allocator_base<_Tp> 
125 { 
126 public: 
127 typedef _Tp value_type; 
128 typedef size_t size_type; 
129 typedef ptrdiff_t difference_type; 
130 
131#if __cplusplus <= 201703L 
132 // These were removed for C++20. 
133 typedef _Tp* pointer; 
134 typedef const _Tp* const_pointer; 
135 typedef _Tp& reference; 
136 typedef const _Tp& const_reference; 
137 
138 template<typename _Tp1> 
139 struct rebind 
140 { typedef allocator<_Tp1> other; }; 
141#endif 
142 
143#if __cplusplus >= 201103L 
144 // _GLIBCXX_RESOLVE_LIB_DEFECTS 
145 // 2103. std::allocator propagate_on_container_move_assignment 
146 using propagate_on_container_move_assignment = true_type; 
147 
148 using is_always_equal 
149 _GLIBCXX20_DEPRECATED_SUGGEST("std::allocator_traits::is_always_equal") 
150 = true_type; 
151#endif 
152 
153 // _GLIBCXX_RESOLVE_LIB_DEFECTS 
154 // 3035. std::allocator's constructors should be constexpr 
155 _GLIBCXX20_CONSTEXPR 
156 allocator() _GLIBCXX_NOTHROW { } 
157 
158 _GLIBCXX20_CONSTEXPR 
159 allocator(const allocator& __a) _GLIBCXX_NOTHROW 
160 : __allocator_base<_Tp>(__a) { } 
161 
162#if __cplusplus >= 201103L 
163 // Avoid implicit deprecation. 
164 allocator& operator=(const allocator&) = default; 
165#endif 
166 
167 template<typename _Tp1> 
168 _GLIBCXX20_CONSTEXPR 
169 allocator(const allocator<_Tp1>&) _GLIBCXX_NOTHROW { } 
170 
171#if __cpp_constexpr_dynamic_alloc 
172 constexpr 
173#endif 
174 ~allocator() _GLIBCXX_NOTHROW { } 
175 
176#if __cplusplus > 201703L 
177 [[nodiscard,__gnu__::__always_inline__]] 
178 constexpr _Tp* 
179 allocate(size_t __n) 
180 { 
181#ifdef __cpp_lib_is_constant_evaluated 
182 if (std::is_constant_evaluated()) 
183 return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp))); 
184#endif 
185 return __allocator_base<_Tp>::allocate(__n, 0); 
186 } 
187 
188 [[__gnu__::__always_inline__]] 
189 constexpr void 
190 deallocate(_Tp* __p, size_t __n) 
191 { 
192#ifdef __cpp_lib_is_constant_evaluated 
193 if (std::is_constant_evaluated()) 
194 { 
195 ::operator delete(__p); 
196 return; 
197 } 
198#endif 
199 __allocator_base<_Tp>::deallocate(__p, __n); 
200 } 
201#endif // C++20 
202 
203 friend _GLIBCXX20_CONSTEXPR bool 
204 operator==(const allocator&, const allocator&) _GLIBCXX_NOTHROW 
205 { return true; } 
206 
207#if __cpp_impl_three_way_comparison < 201907L 
208 friend _GLIBCXX20_CONSTEXPR bool 
209 operator!=(const allocator&, const allocator&) _GLIBCXX_NOTHROW 
210 { return false; } 
211#endif 
212 
213 // Inherit everything else. 
214 }; 
215 
216 template<typename _T1, typename _T2> 
217 inline _GLIBCXX20_CONSTEXPR bool 
218 operator==(const allocator<_T1>&, const allocator<_T2>&) 
219 _GLIBCXX_NOTHROW 
220 { return true; } 
221 
222#if __cpp_impl_three_way_comparison < 201907L 
223 template<typename _T1, typename _T2> 
224 inline _GLIBCXX20_CONSTEXPR bool 
225 operator!=(const allocator<_T1>&, const allocator<_T2>&) 
226 _GLIBCXX_NOTHROW 
227 { return false; } 
228#endif 
229 
230 // Invalid allocator<cv T> partial specializations. 
231 // allocator_traits::rebind_alloc can be used to form a valid allocator type. 
232 template<typename _Tp> 
233 class allocator<const _Tp> 
234 { 
235 public: 
236 typedef _Tp value_type; 
237 template<typename _Up> allocator(const allocator<_Up>&) { } 
238 }; 
239 
240 template<typename _Tp> 
241 class allocator<volatile _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<const volatile _Tp> 
250 { 
251 public: 
252 typedef _Tp value_type; 
253 template<typename _Up> allocator(const allocator<_Up>&) { } 
254 }; 
255 
256 /// @} group allocator 
257 
258 // Inhibit implicit instantiations for required instantiations, 
259 // which are defined via explicit instantiations elsewhere. 
260#if _GLIBCXX_EXTERN_TEMPLATE 
261 extern template class allocator<char>; 
262 extern template class allocator<wchar_t>; 
263#endif 
264 
265 // Undefine. 
266#undef __allocator_base 
267 
268 // To implement Option 3 of DR 431. 
269 template<typename _Alloc, bool = __is_empty(_Alloc)> 
270 struct __alloc_swap 
271 { static void _S_do_it(_Alloc&, _Alloc&) _GLIBCXX_NOEXCEPT { } }; 
272 
273 template<typename _Alloc> 
274 struct __alloc_swap<_Alloc, false> 
275 { 
276 static void 
277 _S_do_it(_Alloc& __one, _Alloc& __two) _GLIBCXX_NOEXCEPT 
278 { 
279 // Precondition: swappable allocators. 
280 if (__one != __two) 
281 swap(__one, __two); 
282 } 
283 }; 
284 
285 // Optimize for stateless allocators. 
286 template<typename _Alloc, bool = __is_empty(_Alloc)> 
287 struct __alloc_neq 
288 { 
289 static bool 
290 _S_do_it(const _Alloc&, const _Alloc&) 
291 { return false; } 
292 }; 
293 
294 template<typename _Alloc> 
295 struct __alloc_neq<_Alloc, false> 
296 { 
297 static bool 
298 _S_do_it(const _Alloc& __one, const _Alloc& __two) 
299 { return __one != __two; } 
300 }; 
301 
302#if __cplusplus >= 201103L 
303 template<typename _Tp, bool 
304 = __or_<is_copy_constructible<typename _Tp::value_type>, 
305 is_nothrow_move_constructible<typename _Tp::value_type>>::value> 
306 struct __shrink_to_fit_aux 
307 { static bool _S_do_it(_Tp&) noexcept { return false; } }; 
308 
309 template<typename _Tp> 
310 struct __shrink_to_fit_aux<_Tp, true> 
311 { 
312 static bool 
313 _S_do_it(_Tp& __c) noexcept 
314 { 
315#if __cpp_exceptions 
316 try 
317 { 
318 _Tp(__make_move_if_noexcept_iterator(__c.begin()), 
319 __make_move_if_noexcept_iterator(__c.end()), 
320 __c.get_allocator()).swap(__c); 
321 return true; 
322 } 
323 catch(...) 
324 { return false; } 
325#else 
326 return false; 
327#endif 
328 } 
329 }; 
330#endif 
331 
332_GLIBCXX_END_NAMESPACE_VERSION 
333} // namespace std 
334 
335#endif 
336