1 // Move, forward and identity for C++11 + swap -*- C++ -*-
2
3 // Copyright (C) 2007-2017 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
36 namespace 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 _GLIBCXX_END_NAMESPACE_VERSION
51 } // namespace
52
53 #if __cplusplus >= 201103L
54 #include <type_traits> // Brings in std::declval too.
55
56 namespace std _GLIBCXX_VISIBILITY(default)
57 {
58 _GLIBCXX_BEGIN_NAMESPACE_VERSION
59
60 /**
61 * @addtogroup utilities
62 * @{
63 */
64
65 /**
66 * @brief Forward an lvalue.
67 * @return The parameter cast to the specified type.
68 *
69 * This function is used to implement "perfect forwarding".
70 */
71 template<typename _Tp>
72 constexpr _Tp&&
73 forward(typename std::remove_reference<_Tp>::type& __t) noexcept
74 { return static_cast<_Tp&&>(__t); }
75
76 /**
77 * @brief Forward an rvalue.
78 * @return The parameter cast to the specified type.
79 *
80 * This function is used to implement "perfect forwarding".
81 */
82 template<typename _Tp>
83 constexpr _Tp&&
84 forward(typename std::remove_reference<_Tp>::type&& __t) noexcept
85 {
86 static_assert(!std::is_lvalue_reference<_Tp>::value, "template argument"
87 " substituting _Tp is an lvalue reference type");
88 return static_cast<_Tp&&>(__t);
89 }
90
91 /**
92 * @brief Convert a value to an rvalue.
93 * @param __t A thing of arbitrary type.
94 * @return The parameter cast to an rvalue-reference to allow moving it.
95 */
96 template<typename _Tp>
97 constexpr typename std::remove_reference<_Tp>::type&&
98 move(_Tp&& __t) noexcept
99 { return static_cast<typename std::remove_reference<_Tp>::type&&>(__t); }
100
101
102 template<typename _Tp>
103 struct __move_if_noexcept_cond
104 : public __and_<__not_<is_nothrow_move_constructible<_Tp>>,
105 is_copy_constructible<_Tp>>::type { };
106
107 /**
108 * @brief Conditionally convert a value to an rvalue.
109 * @param __x A thing of arbitrary type.
110 * @return The parameter, possibly cast to an rvalue-reference.
111 *
112 * Same as std::move unless the type's move constructor could throw and the
113 * type is copyable, in which case an lvalue-reference is returned instead.
114 */
115 template<typename _Tp>
116 constexpr typename
117 conditional<__move_if_noexcept_cond<_Tp>::value, const _Tp&, _Tp&&>::type
118 move_if_noexcept(_Tp& __x) noexcept
119 { return std::move(__x); }
120
121 // declval, from type_traits.
122
123 #if __cplusplus > 201402L
124 // _GLIBCXX_RESOLVE_LIB_DEFECTS
125 // 2296. std::addressof should be constexpr
126 # define __cpp_lib_addressof_constexpr 201603
127 #endif
128 /**
129 * @brief Returns the actual address of the object or function
130 * referenced by r, even in the presence of an overloaded
131 * operator&.
132 * @param __r Reference to an object or function.
133 * @return The actual address.
134 */
135 template<typename _Tp>
136 inline _GLIBCXX17_CONSTEXPR _Tp*
137 addressof(_Tp& __r) noexcept
138 { return std::__addressof(__r); }
139
140 // _GLIBCXX_RESOLVE_LIB_DEFECTS
141 // 2598. addressof works on temporaries
142 template<typename _Tp>
143 const _Tp* addressof(const _Tp&&) = delete;
144
145 // C++11 version of std::exchange for internal use.
146 template <typename _Tp, typename _Up = _Tp>
147 inline _Tp
148 __exchange(_Tp& __obj, _Up&& __new_val)
149 {
150 _Tp __old_val = std::move(__obj);
151 __obj = std::forward<_Up>(__new_val);
152 return __old_val;
153 }
154
155 /// @} group utilities
156 _GLIBCXX_END_NAMESPACE_VERSION
157 } // namespace
158
159 #define _GLIBCXX_MOVE(__val) std::move(__val)
160 #define _GLIBCXX_FORWARD(_Tp, __val) std::forward<_Tp>(__val)
161 #else
162 #define _GLIBCXX_MOVE(__val) (__val)
163 #define _GLIBCXX_FORWARD(_Tp, __val) (__val)
164 #endif
165
166 namespace std _GLIBCXX_VISIBILITY(default)
167 {
168 _GLIBCXX_BEGIN_NAMESPACE_VERSION
169
170 /**
171 * @addtogroup utilities
172 * @{
173 */
174
175 /**
176 * @brief Swaps two values.
177 * @param __a A thing of arbitrary type.
178 * @param __b Another thing of arbitrary type.
179 * @return Nothing.
180 */
181 template<typename _Tp>
182 inline
183 #if __cplusplus >= 201103L
184 typename enable_if<__and_<__not_<__is_tuple_like<_Tp>>,
185 is_move_constructible<_Tp>,
186 is_move_assignable<_Tp>>::value>::type
187 swap(_Tp& __a, _Tp& __b)
188 noexcept(__and_<is_nothrow_move_constructible<_Tp>,
189 is_nothrow_move_assignable<_Tp>>::value)
190 #else
191 void
192 swap(_Tp& __a, _Tp& __b)
193 #endif
194 {
195 // concept requirements
196 __glibcxx_function_requires(_SGIAssignableConcept<_Tp>)
197
198 _Tp __tmp = _GLIBCXX_MOVE(__a);
199 __a = _GLIBCXX_MOVE(__b);
200 __b = _GLIBCXX_MOVE(__tmp);
201 }
202
203 // _GLIBCXX_RESOLVE_LIB_DEFECTS
204 // DR 809. std::swap should be overloaded for array types.
205 /// Swap the contents of two arrays.
206 template<typename _Tp, size_t _Nm>
207 inline
208 #if __cplusplus >= 201103L
209 typename enable_if<__is_swappable<_Tp>::value>::type
210 swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm])
211 noexcept(__is_nothrow_swappable<_Tp>::value)
212 #else
213 void
214 swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm])
215 #endif
216 {
217 for (size_t __n = 0; __n < _Nm; ++__n)
218 swap(__a[__n], __b[__n]);
219 }
220
221 /// @} group utilities
222 _GLIBCXX_END_NAMESPACE_VERSION
223 } // namespace
224
225 #endif /* _MOVE_H */
226