contrib/gcc-8.0/libstdc++-v3/include/bits/move.h

   1 // Move, forward and identity for C++11 + swap -*- C++ -*-
   2
   3 // Copyright (C) 2007-2018 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 #if __cplusplus >= 201103L
  51
  52 _GLIBCXX_END_NAMESPACE_VERSION
  53 } // namespace
  54
  55 #include <type_traits> // Brings in std::declval too.
  56
  57 namespace 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 */