libstdc++
move.h
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1// Move, forward and identity for C++11 + swap -*- C++ -*-
2
3// Copyright (C) 2007-2020 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/** @file bits/move.h
26 * This is an internal header file, included by other library headers.
27 * Do not attempt to use it directly. @headername{utility}
28 */
29
30#ifndef _MOVE_H
31#define _MOVE_H 1
32
33#include <bits/c++config.h>
34#if __cplusplus < 201103L
35# include <bits/concept_check.h>
36#endif
37
38namespace std _GLIBCXX_VISIBILITY(default)
39{
40_GLIBCXX_BEGIN_NAMESPACE_VERSION
41
42 // Used, in C++03 mode too, by allocators, etc.
43 /**
44 * @brief Same as C++11 std::addressof
45 * @ingroup utilities
46 */
47 template<typename _Tp>
48 inline _GLIBCXX_CONSTEXPR _Tp*
50 { return __builtin_addressof(__r); }
51
52#if __cplusplus >= 201103L
53
54_GLIBCXX_END_NAMESPACE_VERSION
55} // namespace
56
57#include <type_traits> // Brings in std::declval too.
58
59namespace std _GLIBCXX_VISIBILITY(default)
60{
61_GLIBCXX_BEGIN_NAMESPACE_VERSION
62
63 /**
64 * @addtogroup utilities
65 * @{
66 */
67
68 /**
69 * @brief Forward an lvalue.
70 * @return The parameter cast to the specified type.
71 *
72 * This function is used to implement "perfect forwarding".
73 */
74 template<typename _Tp>
75 constexpr _Tp&&
77 { return static_cast<_Tp&&>(__t); }
78
79 /**
80 * @brief Forward an rvalue.
81 * @return The parameter cast to the specified type.
82 *
83 * This function is used to implement "perfect forwarding".
84 */
85 template<typename _Tp>
86 constexpr _Tp&&
88 {
90 "std::forward must not be used to convert an rvalue to an lvalue");
91 return static_cast<_Tp&&>(__t);
92 }
93
94 /**
95 * @brief Convert a value to an rvalue.
96 * @param __t A thing of arbitrary type.
97 * @return The parameter cast to an rvalue-reference to allow moving it.
98 */
99 template<typename _Tp>
100 constexpr typename std::remove_reference<_Tp>::type&&
101 move(_Tp&& __t) noexcept
102 { return static_cast<typename std::remove_reference<_Tp>::type&&>(__t); }
103
104
105 template<typename _Tp>
106 struct __move_if_noexcept_cond
107 : public __and_<__not_<is_nothrow_move_constructible<_Tp>>,
108 is_copy_constructible<_Tp>>::type { };
109
110 /**
111 * @brief Conditionally convert a value to an rvalue.
112 * @param __x A thing of arbitrary type.
113 * @return The parameter, possibly cast to an rvalue-reference.
114 *
115 * Same as std::move unless the type's move constructor could throw and the
116 * type is copyable, in which case an lvalue-reference is returned instead.
117 */
118 template<typename _Tp>
119 constexpr typename
120 conditional<__move_if_noexcept_cond<_Tp>::value, const _Tp&, _Tp&&>::type
121 move_if_noexcept(_Tp& __x) noexcept
122 { return std::move(__x); }
123
124 // declval, from type_traits.
125
126#if __cplusplus > 201402L
127 // _GLIBCXX_RESOLVE_LIB_DEFECTS
128 // 2296. std::addressof should be constexpr
129# define __cpp_lib_addressof_constexpr 201603
130#endif
131 /**
132 * @brief Returns the actual address of the object or function
133 * referenced by r, even in the presence of an overloaded
134 * operator&.
135 * @param __r Reference to an object or function.
136 * @return The actual address.
137 */
138 template<typename _Tp>
139 inline _GLIBCXX17_CONSTEXPR _Tp*
140 addressof(_Tp& __r) noexcept
141 { return std::__addressof(__r); }
142
143 // _GLIBCXX_RESOLVE_LIB_DEFECTS
144 // 2598. addressof works on temporaries
145 template<typename _Tp>
146 const _Tp* addressof(const _Tp&&) = delete;
147
148 // C++11 version of std::exchange for internal use.
149 template <typename _Tp, typename _Up = _Tp>
150 _GLIBCXX20_CONSTEXPR
151 inline _Tp
152 __exchange(_Tp& __obj, _Up&& __new_val)
153 {
154 _Tp __old_val = std::move(__obj);
155 __obj = std::forward<_Up>(__new_val);
156 return __old_val;
157 }
158
159 /// @} group utilities
160
161#define _GLIBCXX_MOVE(__val) std::move(__val)
162#define _GLIBCXX_FORWARD(_Tp, __val) std::forward<_Tp>(__val)
163#else
164#define _GLIBCXX_MOVE(__val) (__val)
165#define _GLIBCXX_FORWARD(_Tp, __val) (__val)
166#endif
167
168 /**
169 * @addtogroup utilities
170 * @{
171 */
172
173 /**
174 * @brief Swaps two values.
175 * @param __a A thing of arbitrary type.
176 * @param __b Another thing of arbitrary type.
177 * @return Nothing.
178 */
179 template<typename _Tp>
180 _GLIBCXX20_CONSTEXPR
181 inline
182#if __cplusplus >= 201103L
183 typename enable_if<__and_<__not_<__is_tuple_like<_Tp>>,
184 is_move_constructible<_Tp>,
185 is_move_assignable<_Tp>>::value>::type
186#else
187 void
188#endif
189 swap(_Tp& __a, _Tp& __b)
192 {
193#if __cplusplus < 201103L
194 // concept requirements
195 __glibcxx_function_requires(_SGIAssignableConcept<_Tp>)
196#endif
197 _Tp __tmp = _GLIBCXX_MOVE(__a);
198 __a = _GLIBCXX_MOVE(__b);
199 __b = _GLIBCXX_MOVE(__tmp);
200 }
201
202 // _GLIBCXX_RESOLVE_LIB_DEFECTS
203 // DR 809. std::swap should be overloaded for array types.
204 /// Swap the contents of two arrays.
205 template<typename _Tp, size_t _Nm>
206 _GLIBCXX20_CONSTEXPR
207 inline
208#if __cplusplus >= 201103L
209 typename enable_if<__is_swappable<_Tp>::value>::type
210#else
211 void
212#endif
213 swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm])
214 _GLIBCXX_NOEXCEPT_IF(__is_nothrow_swappable<_Tp>::value)
215 {
216 for (size_t __n = 0; __n < _Nm; ++__n)
217 swap(__a[__n], __b[__n]);
218 }
219
220 /// @} group utilities
221_GLIBCXX_END_NAMESPACE_VERSION
222} // namespace
223
224#endif /* _MOVE_H */
constexpr _Tp * addressof(_Tp &__r) noexcept
Returns the actual address of the object or function referenced by r, even in the presence of an over...
Definition move.h:140
constexpr std::remove_reference< _Tp >::type && move(_Tp &&__t) noexcept
Convert a value to an rvalue.
Definition move.h:101
constexpr conditional< __move_if_noexcept_cond< _Tp >::value, const_Tp &, _Tp && >::type move_if_noexcept(_Tp &__x) noexcept
Conditionally convert a value to an rvalue.
Definition move.h:121
constexpr _Tp * __addressof(_Tp &__r) noexcept
Same as C++11 std::addressof.
Definition move.h:49
constexpr _Tp && forward(typename std::remove_reference< _Tp >::type &__t) noexcept
Forward an lvalue.
Definition move.h:76
ISO C++ entities toplevel namespace is std.
is_lvalue_reference
Definition type_traits:427