1// Move, forward and identity for C++11 + swap -*- C++ -*-
2
3// Copyright (C) 2007-2019 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#include <bits/concept_check.h>
35
36namespace std _GLIBCXX_VISIBILITY(default)
37{
38_GLIBCXX_BEGIN_NAMESPACE_VERSION
39
40 // Used, in C++03 mode too, by allocators, etc.
41 /**
42 * @brief Same as C++11 std::addressof
43 * @ingroup utilities
44 */
45 template<typename _Tp>
46 inline _GLIBCXX_CONSTEXPR _Tp*
47 __addressof(_Tp& __r) _GLIBCXX_NOEXCEPT
48 { return __builtin_addressof(__r); }
49
50#if __cplusplus >= 201103L
51
52_GLIBCXX_END_NAMESPACE_VERSION
53} // namespace
54
55#include <type_traits> // Brings in std::declval too.
56
57namespace std _GLIBCXX_VISIBILITY(default)
58{
59_GLIBCXX_BEGIN_NAMESPACE_VERSION
60
61 /**
62 * @addtogroup utilities
63 * @{
64 */
65
66 /**
67 * @brief Forward an lvalue.
68 * @return The parameter cast to the specified type.
69 *
70 * This function is used to implement "perfect forwarding".
71 */
72 template<typename _Tp>
73 constexpr _Tp&&
74 forward(typename std::remove_reference<_Tp>::type& __t) noexcept
75 { return static_cast<_Tp&&>(__t); }
76
77 /**
78 * @brief Forward an rvalue.
79 * @return The parameter cast to the specified type.
80 *
81 * This function is used to implement "perfect forwarding".
82 */
83 template<typename _Tp>
84 constexpr _Tp&&
85 forward(typename std::remove_reference<_Tp>::type&& __t) noexcept
86 {
87 static_assert(!std::is_lvalue_reference<_Tp>::value, "template argument"
88 " substituting _Tp is an lvalue reference type");
89 return static_cast<_Tp&&>(__t);
90 }
91
92 /**
93 * @brief Convert a value to an rvalue.
94 * @param __t A thing of arbitrary type.
95 * @return The parameter cast to an rvalue-reference to allow moving it.
96 */
97 template<typename _Tp>
98 constexpr typename std::remove_reference<_Tp>::type&&
99 move(_Tp&& __t) noexcept
100 { return static_cast<typename std::remove_reference<_Tp>::type&&>(__t); }
101
102
103 template<typename _Tp>
104 struct __move_if_noexcept_cond
105 : public __and_<__not_<is_nothrow_move_constructible<_Tp>>,
106 is_copy_constructible<_Tp>>::type { };
107
108 /**
109 * @brief Conditionally convert a value to an rvalue.
110 * @param __x A thing of arbitrary type.
111 * @return The parameter, possibly cast to an rvalue-reference.
112 *
113 * Same as std::move unless the type's move constructor could throw and the
114 * type is copyable, in which case an lvalue-reference is returned instead.
115 */
116 template<typename _Tp>
117 constexpr typename
118 conditional<__move_if_noexcept_cond<_Tp>::value, const _Tp&, _Tp&&>::type
119 move_if_noexcept(_Tp& __x) noexcept
120 { return std::move(__x); }
121
122 // declval, from type_traits.
123
124#if __cplusplus > 201402L
125 // _GLIBCXX_RESOLVE_LIB_DEFECTS
126 // 2296. std::addressof should be constexpr
127# define __cpp_lib_addressof_constexpr 201603
128#endif
129 /**
130 * @brief Returns the actual address of the object or function
131 * referenced by r, even in the presence of an overloaded
132 * operator&.
133 * @param __r Reference to an object or function.
134 * @return The actual address.
135 */
136 template<typename _Tp>
137 inline _GLIBCXX17_CONSTEXPR _Tp*
138 addressof(_Tp& __r) noexcept
139 { return std::__addressof(__r); }
140
141 // _GLIBCXX_RESOLVE_LIB_DEFECTS
142 // 2598. addressof works on temporaries
143 template<typename _Tp>
144 const _Tp* addressof(const _Tp&&) = delete;
145
146 // C++11 version of std::exchange for internal use.
147 template <typename _Tp, typename _Up = _Tp>
148 inline _Tp
149 __exchange(_Tp& __obj, _Up&& __new_val)
150 {
151 _Tp __old_val = std::move(__obj);
152 __obj = std::forward<_Up>(__new_val);
153 return __old_val;
154 }
155
156 /// @} group utilities
157
158#define _GLIBCXX_MOVE(__val) std::move(__val)
159#define _GLIBCXX_FORWARD(_Tp, __val) std::forward<_Tp>(__val)
160#else
161#define _GLIBCXX_MOVE(__val) (__val)
162#define _GLIBCXX_FORWARD(_Tp, __val) (__val)
163#endif
164
165 /**
166 * @addtogroup utilities
167 * @{
168 */
169
170 /**
171 * @brief Swaps two values.
172 * @param __a A thing of arbitrary type.
173 * @param __b Another thing of arbitrary type.
174 * @return Nothing.
175 */
176 template<typename _Tp>
177 inline
178#if __cplusplus >= 201103L
179 typename enable_if<__and_<__not_<__is_tuple_like<_Tp>>,
180 is_move_constructible<_Tp>,
181 is_move_assignable<_Tp>>::value>::type
182 swap(_Tp& __a, _Tp& __b)
183 noexcept(__and_<is_nothrow_move_constructible<_Tp>,
184 is_nothrow_move_assignable<_Tp>>::value)
185#else
186 void
187 swap(_Tp& __a, _Tp& __b)
188#endif
189 {
190 // concept requirements
191 __glibcxx_function_requires(_SGIAssignableConcept<_Tp>)
192
193 _Tp __tmp = _GLIBCXX_MOVE(__a);
194 __a = _GLIBCXX_MOVE(__b);
195 __b = _GLIBCXX_MOVE(__tmp);
196 }
197
198 // _GLIBCXX_RESOLVE_LIB_DEFECTS
199 // DR 809. std::swap should be overloaded for array types.
200 /// Swap the contents of two arrays.
201 template<typename _Tp, size_t _Nm>
202 inline
203#if __cplusplus >= 201103L
204 typename enable_if<__is_swappable<_Tp>::value>::type
205 swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm])
206 noexcept(__is_nothrow_swappable<_Tp>::value)
207#else
208 void
209 swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm])
210#endif
211 {
212 for (size_t __n = 0; __n < _Nm; ++__n)
213 swap(__a[__n], __b[__n]);
214 }
215
216 /// @} group utilities
217_GLIBCXX_END_NAMESPACE_VERSION
218} // namespace
219
220#endif /* _MOVE_H */
221