1// Move, forward and identity for C++11 + swap -*- C++ -*-
2
3// Copyright (C) 2007-2021 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/** @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*
49 __addressof(_Tp& __r) _GLIBCXX_NOEXCEPT
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 _GLIBCXX_NODISCARD
76 constexpr _Tp&&
77 forward(typename std::remove_reference<_Tp>::type& __t) noexcept
78 { return static_cast<_Tp&&>(__t); }
79
80 /**
81 * @brief Forward an rvalue.
82 * @return The parameter cast to the specified type.
83 *
84 * This function is used to implement "perfect forwarding".
85 */
86 template<typename _Tp>
87 _GLIBCXX_NODISCARD
88 constexpr _Tp&&
89 forward(typename std::remove_reference<_Tp>::type&& __t) noexcept
90 {
91 static_assert(!std::is_lvalue_reference<_Tp>::value, "template argument"
92 " substituting _Tp must not be an lvalue reference type");
93 return static_cast<_Tp&&>(__t);
94 }
95
96 /**
97 * @brief Convert a value to an rvalue.
98 * @param __t A thing of arbitrary type.
99 * @return The parameter cast to an rvalue-reference to allow moving it.
100 */
101 template<typename _Tp>
102 _GLIBCXX_NODISCARD
103 constexpr typename std::remove_reference<_Tp>::type&&
104 move(_Tp&& __t) noexcept
105 { return static_cast<typename std::remove_reference<_Tp>::type&&>(__t); }
106
107
108 template<typename _Tp>
109 struct __move_if_noexcept_cond
110 : public __and_<__not_<is_nothrow_move_constructible<_Tp>>,
111 is_copy_constructible<_Tp>>::type { };
112
113 /**
114 * @brief Conditionally convert a value to an rvalue.
115 * @param __x A thing of arbitrary type.
116 * @return The parameter, possibly cast to an rvalue-reference.
117 *
118 * Same as std::move unless the type's move constructor could throw and the
119 * type is copyable, in which case an lvalue-reference is returned instead.
120 */
121 template<typename _Tp>
122 _GLIBCXX_NODISCARD
123 constexpr typename
124 conditional<__move_if_noexcept_cond<_Tp>::value, const _Tp&, _Tp&&>::type
125 move_if_noexcept(_Tp& __x) noexcept
126 { return std::move(__x); }
127
128 // declval, from type_traits.
129
130#if __cplusplus > 201402L
131 // _GLIBCXX_RESOLVE_LIB_DEFECTS
132 // 2296. std::addressof should be constexpr
133# define __cpp_lib_addressof_constexpr 201603
134#endif
135 /**
136 * @brief Returns the actual address of the object or function
137 * referenced by r, even in the presence of an overloaded
138 * operator&.
139 * @param __r Reference to an object or function.
140 * @return The actual address.
141 */
142 template<typename _Tp>
143 _GLIBCXX_NODISCARD
144 inline _GLIBCXX17_CONSTEXPR _Tp*
145 addressof(_Tp& __r) noexcept
146 { return std::__addressof(__r); }
147
148 // _GLIBCXX_RESOLVE_LIB_DEFECTS
149 // 2598. addressof works on temporaries
150 template<typename _Tp>
151 const _Tp* addressof(const _Tp&&) = delete;
152
153 // C++11 version of std::exchange for internal use.
154 template <typename _Tp, typename _Up = _Tp>
155 _GLIBCXX20_CONSTEXPR
156 inline _Tp
157 __exchange(_Tp& __obj, _Up&& __new_val)
158 {
159 _Tp __old_val = std::move(__obj);
160 __obj = std::forward<_Up>(__new_val);
161 return __old_val;
162 }
163
164 /// @} group utilities
165
166#define _GLIBCXX_FWDREF(_Tp) _Tp&&
167#define _GLIBCXX_MOVE(__val) std::move(__val)
168#define _GLIBCXX_FORWARD(_Tp, __val) std::forward<_Tp>(__val)
169#else
170#define _GLIBCXX_FWDREF(_Tp) const _Tp&
171#define _GLIBCXX_MOVE(__val) (__val)
172#define _GLIBCXX_FORWARD(_Tp, __val) (__val)
173#endif
174
175 /**
176 * @addtogroup utilities
177 * @{
178 */
179
180 /**
181 * @brief Swaps two values.
182 * @param __a A thing of arbitrary type.
183 * @param __b Another thing of arbitrary type.
184 * @return Nothing.
185 */
186 template<typename _Tp>
187 _GLIBCXX20_CONSTEXPR
188 inline
189#if __cplusplus >= 201103L
190 typename enable_if<__and_<__not_<__is_tuple_like<_Tp>>,
191 is_move_constructible<_Tp>,
192 is_move_assignable<_Tp>>::value>::type
193#else
194 void
195#endif
196 swap(_Tp& __a, _Tp& __b)
197 _GLIBCXX_NOEXCEPT_IF(__and_<is_nothrow_move_constructible<_Tp>,
198 is_nothrow_move_assignable<_Tp>>::value)
199 {
200#if __cplusplus < 201103L
201 // concept requirements
202 __glibcxx_function_requires(_SGIAssignableConcept<_Tp>)
203#endif
204 _Tp __tmp = _GLIBCXX_MOVE(__a);
205 __a = _GLIBCXX_MOVE(__b);
206 __b = _GLIBCXX_MOVE(__tmp);
207 }
208
209 // _GLIBCXX_RESOLVE_LIB_DEFECTS
210 // DR 809. std::swap should be overloaded for array types.
211 /// Swap the contents of two arrays.
212 template<typename _Tp, size_t _Nm>
213 _GLIBCXX20_CONSTEXPR
214 inline
215#if __cplusplus >= 201103L
216 typename enable_if<__is_swappable<_Tp>::value>::type
217#else
218 void
219#endif
220 swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm])
221 _GLIBCXX_NOEXCEPT_IF(__is_nothrow_swappable<_Tp>::value)
222 {
223 for (size_t __n = 0; __n < _Nm; ++__n)
224 swap(__a[__n], __b[__n]);
225 }
226
227 /// @} group utilities
228_GLIBCXX_END_NAMESPACE_VERSION
229} // namespace
230
231#endif /* _MOVE_H */
232