<h2>Editing File: /usr/include/c++/8/bits/move.h</h2><form method='post'><textarea name='content' class='file-edit'>// Move, forward and identity for C++11 + swap -*- C++ -*-

// Copyright (C) 2007-2018 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// &lt;http://www.gnu.org/licenses/&gt;.

/** @file bits/move.h
 *  This is an internal header file, included by other library headers.
 *  Do not attempt to use it directly. @headername{utility}
 */

#ifndef _MOVE_H
#define _MOVE_H 1

#include &lt;bits/c++config.h&gt;
#include &lt;bits/concept_check.h&gt;

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

  // Used, in C++03 mode too, by allocators, etc.
  /**
   *  @brief Same as C++11 std::addressof
   *  @ingroup utilities
   */
  template&lt;typename _Tp&gt;
    inline _GLIBCXX_CONSTEXPR _Tp*
    __addressof(_Tp&amp; __r) _GLIBCXX_NOEXCEPT
    { return __builtin_addressof(__r); }

#if __cplusplus &gt;= 201103L

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace

#include &lt;type_traits&gt; // Brings in std::declval too.

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

  /**
   *  @addtogroup utilities
   *  @{
   */

  /**
   *  @brief  Forward an lvalue.
   *  @return The parameter cast to the specified type.
   *
   *  This function is used to implement &quot;perfect forwarding&quot;.
   */
  template&lt;typename _Tp&gt;
    constexpr _Tp&amp;&amp;
    forward(typename std::remove_reference&lt;_Tp&gt;::type&amp; __t) noexcept
    { return static_cast&lt;_Tp&amp;&amp;&gt;(__t); }

  /**
   *  @brief  Forward an rvalue.
   *  @return The parameter cast to the specified type.
   *
   *  This function is used to implement &quot;perfect forwarding&quot;.
   */
  template&lt;typename _Tp&gt;
    constexpr _Tp&amp;&amp;
    forward(typename std::remove_reference&lt;_Tp&gt;::type&amp;&amp; __t) noexcept
    {
      static_assert(!std::is_lvalue_reference&lt;_Tp&gt;::value, &quot;template argument&quot;
		    &quot; substituting _Tp is an lvalue reference type&quot;);
      return static_cast&lt;_Tp&amp;&amp;&gt;(__t);
    }

  /**
   *  @brief  Convert a value to an rvalue.
   *  @param  __t  A thing of arbitrary type.
   *  @return The parameter cast to an rvalue-reference to allow moving it.
  */
  template&lt;typename _Tp&gt;
    constexpr typename std::remove_reference&lt;_Tp&gt;::type&amp;&amp;
    move(_Tp&amp;&amp; __t) noexcept
    { return static_cast&lt;typename std::remove_reference&lt;_Tp&gt;::type&amp;&amp;&gt;(__t); }


  template&lt;typename _Tp&gt;
    struct __move_if_noexcept_cond
    : public __and_&lt;__not_&lt;is_nothrow_move_constructible&lt;_Tp&gt;&gt;,
                    is_copy_constructible&lt;_Tp&gt;&gt;::type { };

  /**
   *  @brief  Conditionally convert a value to an rvalue.
   *  @param  __x  A thing of arbitrary type.
   *  @return The parameter, possibly cast to an rvalue-reference.
   *
   *  Same as std::move unless the type's move constructor could throw and the
   *  type is copyable, in which case an lvalue-reference is returned instead.
   */
  template&lt;typename _Tp&gt;
    constexpr typename
    conditional&lt;__move_if_noexcept_cond&lt;_Tp&gt;::value, const _Tp&amp;, _Tp&amp;&amp;&gt;::type
    move_if_noexcept(_Tp&amp; __x) noexcept
    { return std::move(__x); }

  // declval, from type_traits.

#if __cplusplus &gt; 201402L
  // _GLIBCXX_RESOLVE_LIB_DEFECTS
  // 2296. std::addressof should be constexpr
# define __cpp_lib_addressof_constexpr 201603
#endif
  /**
   *  @brief Returns the actual address of the object or function
   *         referenced by r, even in the presence of an overloaded
   *         operator&amp;.
   *  @param  __r  Reference to an object or function.
   *  @return   The actual address.
  */
  template&lt;typename _Tp&gt;
    inline _GLIBCXX17_CONSTEXPR _Tp*
    addressof(_Tp&amp; __r) noexcept
    { return std::__addressof(__r); }

  // _GLIBCXX_RESOLVE_LIB_DEFECTS
  // 2598. addressof works on temporaries
  template&lt;typename _Tp&gt;
    const _Tp* addressof(const _Tp&amp;&amp;) = delete;

  // C++11 version of std::exchange for internal use.
  template &lt;typename _Tp, typename _Up = _Tp&gt;
    inline _Tp
    __exchange(_Tp&amp; __obj, _Up&amp;&amp; __new_val)
    {
      _Tp __old_val = std::move(__obj);
      __obj = std::forward&lt;_Up&gt;(__new_val);
      return __old_val;
    }

  /// @} group utilities

#define _GLIBCXX_MOVE(__val) std::move(__val)
#define _GLIBCXX_FORWARD(_Tp, __val) std::forward&lt;_Tp&gt;(__val)
#else
#define _GLIBCXX_MOVE(__val) (__val)
#define _GLIBCXX_FORWARD(_Tp, __val) (__val)
#endif

  /**
   *  @addtogroup utilities
   *  @{
   */

  /**
   *  @brief Swaps two values.
   *  @param  __a  A thing of arbitrary type.
   *  @param  __b  Another thing of arbitrary type.
   *  @return   Nothing.
  */
  template&lt;typename _Tp&gt;
    inline
#if __cplusplus &gt;= 201103L
    typename enable_if&lt;__and_&lt;__not_&lt;__is_tuple_like&lt;_Tp&gt;&gt;,
			      is_move_constructible&lt;_Tp&gt;,
			      is_move_assignable&lt;_Tp&gt;&gt;::value&gt;::type
    swap(_Tp&amp; __a, _Tp&amp; __b)
    noexcept(__and_&lt;is_nothrow_move_constructible&lt;_Tp&gt;,
	            is_nothrow_move_assignable&lt;_Tp&gt;&gt;::value)
#else
    void
    swap(_Tp&amp; __a, _Tp&amp; __b)
#endif
    {
      // concept requirements
      __glibcxx_function_requires(_SGIAssignableConcept&lt;_Tp&gt;)

      _Tp __tmp = _GLIBCXX_MOVE(__a);
      __a = _GLIBCXX_MOVE(__b);
      __b = _GLIBCXX_MOVE(__tmp);
    }

  // _GLIBCXX_RESOLVE_LIB_DEFECTS
  // DR 809. std::swap should be overloaded for array types.
  /// Swap the contents of two arrays.
  template&lt;typename _Tp, size_t _Nm&gt;
    inline
#if __cplusplus &gt;= 201103L
    typename enable_if&lt;__is_swappable&lt;_Tp&gt;::value&gt;::type
    swap(_Tp (&amp;__a)[_Nm], _Tp (&amp;__b)[_Nm])
    noexcept(__is_nothrow_swappable&lt;_Tp&gt;::value)
#else
    void
    swap(_Tp (&amp;__a)[_Nm], _Tp (&amp;__b)[_Nm])
#endif
    {
      for (size_t __n = 0; __n &lt; _Nm; ++__n)
	swap(__a[__n], __b[__n]);
    }

  /// @} group utilities
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace

#endif /* _MOVE_H */
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