libstdc++-v3/include/bits/move.h

   1 // Move, forward and identity for C++11 + swap -*- C++ -*-
   2
   3 // Copyright (C) 2007-2016 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_<is_move_constructible<_Tp>,
 185                               is_move_assignable<_Tp>>::value>::type
 186     swap(_Tp& __a, _Tp& __b)
 187     noexcept(__and_<is_nothrow_move_constructible<_Tp>,
 188                     is_nothrow_move_assignable<_Tp>>::value)
 189 #else
 190     void
 191     swap(_Tp& __a, _Tp& __b)
 192 #endif
 193     {
 194       // concept requirements
 195       __glibcxx_function_requires(_SGIAssignableConcept<_Tp>)
 196
 197       _Tp __tmp = _GLIBCXX_MOVE(__a);
 198       __a = _GLIBCXX_MOVE(__b);
 199       __b = _GLIBCXX_MOVE(__tmp);
 200     }
 201
 202   // _GLIBCXX_RESOLVE_LIB_DEFECTS
 203   // DR 809. std::swap should be overloaded for array types.
 204   /// Swap the contents of two arrays.
 205   template<typename _Tp, size_t _Nm>
 206     inline
 207 #if __cplusplus >= 201103L
 208     typename enable_if<__is_swappable<_Tp>::value>::type
 209     swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm])
 210     noexcept(__is_nothrow_swappable<_Tp>::value)
 211 #else
 212     void
 213     swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm])
 214 #endif
 215     {
 216       for (size_t __n = 0; __n < _Nm; ++__n)
 217         swap(__a[__n], __b[__n]);
 218     }
 219
 220   /// @} group utilities
 221 _GLIBCXX_END_NAMESPACE_VERSION
 222 } // namespace
 223
 224 #endif /* _MOVE_H */