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