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, 
92 "std::forward must not be used to convert an rvalue to an lvalue"); 
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