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       1             : // Move, forward and identity for C++11 + swap -*- C++ -*-
       2             : 
       3             : // Copyright (C) 2007-2022 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             : 
      38             : namespace 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             : 
      59             : namespace 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
     124             :     __conditional_t<__move_if_noexcept_cond<_Tp>::value, const _Tp&, _Tp&&>
     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 201603L
     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    11932322 :     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    11932322 :       _Tp __tmp = _GLIBCXX_MOVE(__a);
     205    11932510 :       __a = _GLIBCXX_MOVE(__b);
     206    10756181 :       __b = _GLIBCXX_MOVE(__tmp);
     207    11865167 :     }
     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 */