libstdc++
uses_allocator.h
1 // Uses-allocator Construction -*- C++ -*-
2 
3 // Copyright (C) 2010-2021 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 #ifndef _USES_ALLOCATOR_H
26 #define _USES_ALLOCATOR_H 1
27 
28 #if __cplusplus < 201103L
29 # include <bits/c++0x_warning.h>
30 #else
31 
32 #include <type_traits>
33 #include <bits/move.h>
34 
35 namespace std _GLIBCXX_VISIBILITY(default)
36 {
37 _GLIBCXX_BEGIN_NAMESPACE_VERSION
38 
39  // This is used for std::experimental::erased_type from Library Fundamentals.
40  struct __erased_type { };
41 
42  // This also supports the "type-erased allocator" protocol from the
43  // Library Fundamentals TS, where allocator_type is erased_type.
44  // The second condition will always be false for types not using the TS.
45  template<typename _Alloc, typename _Tp>
46  using __is_erased_or_convertible
47  = __or_<is_convertible<_Alloc, _Tp>, is_same<_Tp, __erased_type>>;
48 
49  /// [allocator.tag]
50  struct allocator_arg_t { explicit allocator_arg_t() = default; };
51 
52  _GLIBCXX17_INLINE constexpr allocator_arg_t allocator_arg =
54 
55  template<typename _Tp, typename _Alloc, typename = __void_t<>>
56  struct __uses_allocator_helper
57  : false_type { };
58 
59  template<typename _Tp, typename _Alloc>
60  struct __uses_allocator_helper<_Tp, _Alloc,
61  __void_t<typename _Tp::allocator_type>>
62  : __is_erased_or_convertible<_Alloc, typename _Tp::allocator_type>::type
63  { };
64 
65  /// [allocator.uses.trait]
66  template<typename _Tp, typename _Alloc>
68  : __uses_allocator_helper<_Tp, _Alloc>::type
69  { };
70 
71  struct __uses_alloc_base { };
72 
73  struct __uses_alloc0 : __uses_alloc_base
74  {
75  struct _Sink { void _GLIBCXX20_CONSTEXPR operator=(const void*) { } } _M_a;
76  };
77 
78  template<typename _Alloc>
79  struct __uses_alloc1 : __uses_alloc_base { const _Alloc* _M_a; };
80 
81  template<typename _Alloc>
82  struct __uses_alloc2 : __uses_alloc_base { const _Alloc* _M_a; };
83 
84  template<bool, typename _Tp, typename _Alloc, typename... _Args>
85  struct __uses_alloc;
86 
87  template<typename _Tp, typename _Alloc, typename... _Args>
88  struct __uses_alloc<true, _Tp, _Alloc, _Args...>
89  : conditional<
90  is_constructible<_Tp, allocator_arg_t, const _Alloc&, _Args...>::value,
91  __uses_alloc1<_Alloc>,
92  __uses_alloc2<_Alloc>>::type
93  {
94  // _GLIBCXX_RESOLVE_LIB_DEFECTS
95  // 2586. Wrong value category used in scoped_allocator_adaptor::construct
96  static_assert(__or_<
97  is_constructible<_Tp, allocator_arg_t, const _Alloc&, _Args...>,
98  is_constructible<_Tp, _Args..., const _Alloc&>>::value,
99  "construction with an allocator must be possible"
100  " if uses_allocator is true");
101  };
102 
103  template<typename _Tp, typename _Alloc, typename... _Args>
104  struct __uses_alloc<false, _Tp, _Alloc, _Args...>
105  : __uses_alloc0 { };
106 
107  template<typename _Tp, typename _Alloc, typename... _Args>
108  using __uses_alloc_t =
109  __uses_alloc<uses_allocator<_Tp, _Alloc>::value, _Tp, _Alloc, _Args...>;
110 
111  template<typename _Tp, typename _Alloc, typename... _Args>
112  _GLIBCXX20_CONSTEXPR
113  inline __uses_alloc_t<_Tp, _Alloc, _Args...>
114  __use_alloc(const _Alloc& __a)
115  {
116  __uses_alloc_t<_Tp, _Alloc, _Args...> __ret;
117  __ret._M_a = std::__addressof(__a);
118  return __ret;
119  }
120 
121  template<typename _Tp, typename _Alloc, typename... _Args>
122  void
123  __use_alloc(const _Alloc&&) = delete;
124 
125 #if __cplusplus > 201402L
126  template <typename _Tp, typename _Alloc>
127  inline constexpr bool uses_allocator_v =
128  uses_allocator<_Tp, _Alloc>::value;
129 #endif // C++17
130 
131  template<template<typename...> class _Predicate,
132  typename _Tp, typename _Alloc, typename... _Args>
133  struct __is_uses_allocator_predicate
134  : conditional<uses_allocator<_Tp, _Alloc>::value,
135  __or_<_Predicate<_Tp, allocator_arg_t, _Alloc, _Args...>,
136  _Predicate<_Tp, _Args..., _Alloc>>,
137  _Predicate<_Tp, _Args...>>::type { };
138 
139  template<typename _Tp, typename _Alloc, typename... _Args>
140  struct __is_uses_allocator_constructible
141  : __is_uses_allocator_predicate<is_constructible, _Tp, _Alloc, _Args...>
142  { };
143 
144 #if __cplusplus >= 201402L
145  template<typename _Tp, typename _Alloc, typename... _Args>
146  _GLIBCXX17_INLINE constexpr bool __is_uses_allocator_constructible_v =
147  __is_uses_allocator_constructible<_Tp, _Alloc, _Args...>::value;
148 #endif // C++14
149 
150  template<typename _Tp, typename _Alloc, typename... _Args>
151  struct __is_nothrow_uses_allocator_constructible
152  : __is_uses_allocator_predicate<is_nothrow_constructible,
153  _Tp, _Alloc, _Args...>
154  { };
155 
156 
157 #if __cplusplus >= 201402L
158  template<typename _Tp, typename _Alloc, typename... _Args>
159  _GLIBCXX17_INLINE constexpr bool
160  __is_nothrow_uses_allocator_constructible_v =
161  __is_nothrow_uses_allocator_constructible<_Tp, _Alloc, _Args...>::value;
162 #endif // C++14
163 
164  template<typename _Tp, typename... _Args>
165  void __uses_allocator_construct_impl(__uses_alloc0 __a, _Tp* __ptr,
166  _Args&&... __args)
167  { ::new ((void*)__ptr) _Tp(std::forward<_Args>(__args)...); }
168 
169  template<typename _Tp, typename _Alloc, typename... _Args>
170  void __uses_allocator_construct_impl(__uses_alloc1<_Alloc> __a, _Tp* __ptr,
171  _Args&&... __args)
172  {
173  ::new ((void*)__ptr) _Tp(allocator_arg, *__a._M_a,
174  std::forward<_Args>(__args)...);
175  }
176 
177  template<typename _Tp, typename _Alloc, typename... _Args>
178  void __uses_allocator_construct_impl(__uses_alloc2<_Alloc> __a, _Tp* __ptr,
179  _Args&&... __args)
180  { ::new ((void*)__ptr) _Tp(std::forward<_Args>(__args)..., *__a._M_a); }
181 
182  template<typename _Tp, typename _Alloc, typename... _Args>
183  void __uses_allocator_construct(const _Alloc& __a, _Tp* __ptr,
184  _Args&&... __args)
185  {
186  std::__uses_allocator_construct_impl(
187  std::__use_alloc<_Tp, _Alloc, _Args...>(__a), __ptr,
188  std::forward<_Args>(__args)...);
189  }
190 
191 _GLIBCXX_END_NAMESPACE_VERSION
192 } // namespace std
193 
194 #endif
195 #endif
constexpr _Tp * __addressof(_Tp &__r) noexcept
Same as C++11 std::addressof.
Definition: move.h:49
ISO C++ entities toplevel namespace is std.
integral_constant
Definition: type_traits:66
Declare uses_allocator so it can be specialized in <queue> etc.
[allocator.tag]