libstdc++
uses_allocator_args.h
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1 // Utility functions for uses-allocator construction -*- C++ -*-
2 
3 // Copyright (C) 2019-2025 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 
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22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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24 
25 /** @file include/bits/uses_allocator_args.h
26  * This is an internal header file, included by other library headers.
27  * Do not attempt to use it directly. @headername{memory}
28  */
29 
30 #ifndef _USES_ALLOCATOR_ARGS
31 #define _USES_ALLOCATOR_ARGS 1
32 
33 #ifdef _GLIBCXX_SYSHDR
34 #pragma GCC system_header
35 #endif
36 
37 #include <bits/version.h>
38 
39 #ifdef __glibcxx_make_obj_using_allocator // C++ >= 20 && concepts
40 #include <new> // for placement operator new
41 #include <tuple> // for tuple, make_tuple, make_from_tuple
42 #include <bits/stl_construct.h> // construct_at
43 #include <bits/stl_pair.h> // pair
44 
45 namespace std _GLIBCXX_VISIBILITY(default)
46 {
47 _GLIBCXX_BEGIN_NAMESPACE_VERSION
48 
49  template<typename _Tp>
50  concept _Std_pair = __is_pair<remove_cv_t<_Tp>>;
51 
52 /** @addtogroup allocators
53  * @{
54  */
55  template<typename _Tp, typename _Alloc, typename... _Args>
56  constexpr auto
57  uses_allocator_construction_args(const _Alloc& __a,
58  _Args&&... __args) noexcept
59  requires (! _Std_pair<_Tp>)
60  {
61  if constexpr (uses_allocator_v<remove_cv_t<_Tp>, _Alloc>)
62  {
63  if constexpr (is_constructible_v<_Tp, allocator_arg_t,
64  const _Alloc&, _Args...>)
65  {
66  return tuple<allocator_arg_t, const _Alloc&, _Args&&...>(
67  allocator_arg, __a, std::forward<_Args>(__args)...);
68  }
69  else
70  {
71  static_assert(is_constructible_v<_Tp, _Args..., const _Alloc&>,
72  "construction with an allocator must be possible"
73  " if uses_allocator is true");
74 
75  return tuple<_Args&&..., const _Alloc&>(
76  std::forward<_Args>(__args)..., __a);
77  }
78  }
79  else
80  {
81  static_assert(is_constructible_v<_Tp, _Args...>);
82 
83  return tuple<_Args&&...>(std::forward<_Args>(__args)...);
84  }
85  }
86 
87  template<_Std_pair _Tp, typename _Alloc, typename _Tuple1, typename _Tuple2>
88  constexpr auto
89  uses_allocator_construction_args(const _Alloc& __a, piecewise_construct_t,
90  _Tuple1&& __x, _Tuple2&& __y) noexcept;
91 
92  template<_Std_pair _Tp, typename _Alloc>
93  constexpr auto
94  uses_allocator_construction_args(const _Alloc&) noexcept;
95 
96  template<_Std_pair _Tp, typename _Alloc, typename _Up, typename _Vp>
97  constexpr auto
98  uses_allocator_construction_args(const _Alloc&, _Up&&, _Vp&&) noexcept;
99 
100  template<_Std_pair _Tp, typename _Alloc, typename _Up, typename _Vp>
101  constexpr auto
102  uses_allocator_construction_args(const _Alloc&,
103  const pair<_Up, _Vp>&) noexcept;
104 
105  template<_Std_pair _Tp, typename _Alloc, typename _Up, typename _Vp>
106  constexpr auto
107  uses_allocator_construction_args(const _Alloc&, pair<_Up, _Vp>&&) noexcept;
108 
109 #if __cplusplus > 202002L
110  template<_Std_pair _Tp, typename _Alloc, typename _Up, typename _Vp>
111  constexpr auto
112  uses_allocator_construction_args(const _Alloc&,
113  pair<_Up, _Vp>&) noexcept;
114 
115  template<_Std_pair _Tp, typename _Alloc, typename _Up, typename _Vp>
116  constexpr auto
117  uses_allocator_construction_args(const _Alloc&, const pair<_Up, _Vp>&&) noexcept;
118 #endif // C++23
119 
120  template<_Std_pair _Tp, typename _Alloc, typename _Tuple1, typename _Tuple2>
121  constexpr auto
122  uses_allocator_construction_args(const _Alloc& __a, piecewise_construct_t,
123  _Tuple1&& __x, _Tuple2&& __y) noexcept
124  {
125  using _Tp1 = typename _Tp::first_type;
126  using _Tp2 = typename _Tp::second_type;
127 
129  std::apply([&__a](auto&&... __args1) {
130  return std::uses_allocator_construction_args<_Tp1>(
131  __a, std::forward<decltype(__args1)>(__args1)...);
132  }, std::forward<_Tuple1>(__x)),
133  std::apply([&__a](auto&&... __args2) {
134  return std::uses_allocator_construction_args<_Tp2>(
135  __a, std::forward<decltype(__args2)>(__args2)...);
136  }, std::forward<_Tuple2>(__y)));
137  }
138 
139  template<_Std_pair _Tp, typename _Alloc>
140  constexpr auto
141  uses_allocator_construction_args(const _Alloc& __a) noexcept
142  {
143  using _Tp1 = typename _Tp::first_type;
144  using _Tp2 = typename _Tp::second_type;
145 
147  std::uses_allocator_construction_args<_Tp1>(__a),
148  std::uses_allocator_construction_args<_Tp2>(__a));
149  }
150 
151  template<_Std_pair _Tp, typename _Alloc, typename _Up, typename _Vp>
152  constexpr auto
153  uses_allocator_construction_args(const _Alloc& __a, _Up&& __u, _Vp&& __v)
154  noexcept
155  {
156  using _Tp1 = typename _Tp::first_type;
157  using _Tp2 = typename _Tp::second_type;
158 
160  std::uses_allocator_construction_args<_Tp1>(__a,
161  std::forward<_Up>(__u)),
162  std::uses_allocator_construction_args<_Tp2>(__a,
163  std::forward<_Vp>(__v)));
164  }
165 
166  template<_Std_pair _Tp, typename _Alloc, typename _Up, typename _Vp>
167  constexpr auto
168  uses_allocator_construction_args(const _Alloc& __a,
169  const pair<_Up, _Vp>& __pr) noexcept
170  {
171  using _Tp1 = typename _Tp::first_type;
172  using _Tp2 = typename _Tp::second_type;
173 
175  std::uses_allocator_construction_args<_Tp1>(__a, __pr.first),
176  std::uses_allocator_construction_args<_Tp2>(__a, __pr.second));
177  }
178 
179  template<_Std_pair _Tp, typename _Alloc, typename _Up, typename _Vp>
180  constexpr auto
181  uses_allocator_construction_args(const _Alloc& __a,
182  pair<_Up, _Vp>&& __pr) noexcept
183  {
184  using _Tp1 = typename _Tp::first_type;
185  using _Tp2 = typename _Tp::second_type;
186 
187  // _GLIBCXX_RESOLVE_LIB_DEFECTS
188  // 3527. uses_allocator_construction_args handles rvalue pairs
189  // of rvalue references incorrectly
191  std::uses_allocator_construction_args<_Tp1>(__a,
192  std::get<0>(std::move(__pr))),
193  std::uses_allocator_construction_args<_Tp2>(__a,
194  std::get<1>(std::move(__pr))));
195  }
196 
197 #if __cplusplus > 202002L
198  template<_Std_pair _Tp, typename _Alloc, typename _Up, typename _Vp>
199  constexpr auto
200  uses_allocator_construction_args(const _Alloc& __a,
201  pair<_Up, _Vp>& __pr) noexcept
202  {
203  using _Tp1 = typename _Tp::first_type;
204  using _Tp2 = typename _Tp::second_type;
205 
207  std::uses_allocator_construction_args<_Tp1>(__a, __pr.first),
208  std::uses_allocator_construction_args<_Tp2>(__a, __pr.second));
209  }
210 
211  template<_Std_pair _Tp, typename _Alloc, typename _Up, typename _Vp>
212  constexpr auto
213  uses_allocator_construction_args(const _Alloc& __a,
214  const pair<_Up, _Vp>&& __pr) noexcept
215  {
216  using _Tp1 = typename _Tp::first_type;
217  using _Tp2 = typename _Tp::second_type;
218 
220  std::uses_allocator_construction_args<_Tp1>(__a,
221  std::get<0>(std::move(__pr))),
222  std::uses_allocator_construction_args<_Tp2>(__a,
223  std::get<1>(std::move(__pr))));
224  }
225 #endif // C++23
226 
227  template<typename _Tp, typename _Alloc, typename... _Args>
228  constexpr _Tp
229  make_obj_using_allocator(const _Alloc& __a, _Args&&... __args)
230  {
231  return std::make_from_tuple<_Tp>(
232  std::uses_allocator_construction_args<_Tp>(__a,
233  std::forward<_Args>(__args)...));
234  }
235 
236  template<typename _Tp, typename _Alloc, typename... _Args>
237  constexpr _Tp*
238  uninitialized_construct_using_allocator(_Tp* __p, const _Alloc& __a,
239  _Args&&... __args)
240  {
241  return std::apply([&](auto&&... __xs) {
242  return std::construct_at(__p, std::forward<decltype(__xs)>(__xs)...);
243  }, std::uses_allocator_construction_args<_Tp>(__a,
244  std::forward<_Args>(__args)...));
245  }
246 /// @}
247 _GLIBCXX_END_NAMESPACE_VERSION
248 } // namespace std
249 #endif // __glibcxx_make_obj_using_allocator
250 #endif // _USES_ALLOCATOR_ARGS
constexpr piecewise_construct_t piecewise_construct
Tag for piecewise construction of std::pair objects.
Definition: stl_pair.h:82
constexpr std::remove_reference< _Tp >::type && move(_Tp &&__t) noexcept
Convert a value to an rvalue.
Definition: move.h:138
constexpr tuple< typename __decay_and_strip< _Elements >::__type... > make_tuple(_Elements &&... __args)
Create a tuple containing copies of the arguments.
Definition: tuple:2666
constexpr _Tp && forward(typename std::remove_reference< _Tp >::type &__t) noexcept
Forward an lvalue.
Definition: move.h:72
ISO C++ entities toplevel namespace is std.