406f58e1e3
Add [[nodiscard]] to functions that are effectively just a static_cast, as per P2351. Also add it to std::addressof. libstdc++-v3/ChangeLog: * include/bits/move.h (forward, move, move_if_noexcept) (addressof): Add _GLIBCXX_NODISCARD. * include/bits/ranges_cmp.h (identity::operator()): Add nodiscard attribute. * include/c_global/cstddef (to_integer): Likewise. * include/std/bit (bit_cast): Likewise. * include/std/utility (as_const, to_underlying): Likewise.
232 lines
6.7 KiB
C++
232 lines
6.7 KiB
C++
// Move, forward and identity for C++11 + swap -*- C++ -*-
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// Copyright (C) 2007-2021 Free Software Foundation, Inc.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the
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// terms of the GNU General Public License as published by the
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// Free Software Foundation; either version 3, or (at your option)
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// any later version.
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// Under Section 7 of GPL version 3, you are granted additional
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// permissions described in the GCC Runtime Library Exception, version
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// 3.1, as published by the Free Software Foundation.
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// You should have received a copy of the GNU General Public License and
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// a copy of the GCC Runtime Library Exception along with this program;
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// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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// <http://www.gnu.org/licenses/>.
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/** @file bits/move.h
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* This is an internal header file, included by other library headers.
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* Do not attempt to use it directly. @headername{utility}
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*/
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#ifndef _MOVE_H
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#define _MOVE_H 1
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#include <bits/c++config.h>
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#if __cplusplus < 201103L
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# include <bits/concept_check.h>
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#endif
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namespace std _GLIBCXX_VISIBILITY(default)
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{
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_GLIBCXX_BEGIN_NAMESPACE_VERSION
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// Used, in C++03 mode too, by allocators, etc.
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/**
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* @brief Same as C++11 std::addressof
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* @ingroup utilities
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*/
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template<typename _Tp>
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inline _GLIBCXX_CONSTEXPR _Tp*
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__addressof(_Tp& __r) _GLIBCXX_NOEXCEPT
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{ return __builtin_addressof(__r); }
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#if __cplusplus >= 201103L
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_GLIBCXX_END_NAMESPACE_VERSION
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} // namespace
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#include <type_traits> // Brings in std::declval too.
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namespace std _GLIBCXX_VISIBILITY(default)
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{
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_GLIBCXX_BEGIN_NAMESPACE_VERSION
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/**
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* @addtogroup utilities
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* @{
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*/
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/**
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* @brief Forward an lvalue.
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* @return The parameter cast to the specified type.
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*
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* This function is used to implement "perfect forwarding".
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*/
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template<typename _Tp>
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_GLIBCXX_NODISCARD
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constexpr _Tp&&
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forward(typename std::remove_reference<_Tp>::type& __t) noexcept
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{ return static_cast<_Tp&&>(__t); }
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/**
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* @brief Forward an rvalue.
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* @return The parameter cast to the specified type.
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*
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* This function is used to implement "perfect forwarding".
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*/
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template<typename _Tp>
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_GLIBCXX_NODISCARD
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constexpr _Tp&&
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forward(typename std::remove_reference<_Tp>::type&& __t) noexcept
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{
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static_assert(!std::is_lvalue_reference<_Tp>::value, "template argument"
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" substituting _Tp must not be an lvalue reference type");
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return static_cast<_Tp&&>(__t);
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}
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/**
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* @brief Convert a value to an rvalue.
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* @param __t A thing of arbitrary type.
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* @return The parameter cast to an rvalue-reference to allow moving it.
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*/
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template<typename _Tp>
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_GLIBCXX_NODISCARD
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constexpr typename std::remove_reference<_Tp>::type&&
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move(_Tp&& __t) noexcept
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{ return static_cast<typename std::remove_reference<_Tp>::type&&>(__t); }
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template<typename _Tp>
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struct __move_if_noexcept_cond
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: public __and_<__not_<is_nothrow_move_constructible<_Tp>>,
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is_copy_constructible<_Tp>>::type { };
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/**
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* @brief Conditionally convert a value to an rvalue.
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* @param __x A thing of arbitrary type.
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* @return The parameter, possibly cast to an rvalue-reference.
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*
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* Same as std::move unless the type's move constructor could throw and the
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* type is copyable, in which case an lvalue-reference is returned instead.
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*/
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template<typename _Tp>
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_GLIBCXX_NODISCARD
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constexpr typename
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conditional<__move_if_noexcept_cond<_Tp>::value, const _Tp&, _Tp&&>::type
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move_if_noexcept(_Tp& __x) noexcept
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{ return std::move(__x); }
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// declval, from type_traits.
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#if __cplusplus > 201402L
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// _GLIBCXX_RESOLVE_LIB_DEFECTS
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// 2296. std::addressof should be constexpr
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# define __cpp_lib_addressof_constexpr 201603
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#endif
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/**
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* @brief Returns the actual address of the object or function
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* referenced by r, even in the presence of an overloaded
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* operator&.
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* @param __r Reference to an object or function.
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* @return The actual address.
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*/
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template<typename _Tp>
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_GLIBCXX_NODISCARD
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inline _GLIBCXX17_CONSTEXPR _Tp*
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addressof(_Tp& __r) noexcept
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{ return std::__addressof(__r); }
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// _GLIBCXX_RESOLVE_LIB_DEFECTS
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// 2598. addressof works on temporaries
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template<typename _Tp>
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const _Tp* addressof(const _Tp&&) = delete;
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// C++11 version of std::exchange for internal use.
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template <typename _Tp, typename _Up = _Tp>
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_GLIBCXX20_CONSTEXPR
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inline _Tp
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__exchange(_Tp& __obj, _Up&& __new_val)
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{
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_Tp __old_val = std::move(__obj);
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__obj = std::forward<_Up>(__new_val);
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return __old_val;
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}
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/// @} group utilities
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#define _GLIBCXX_FWDREF(_Tp) _Tp&&
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#define _GLIBCXX_MOVE(__val) std::move(__val)
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#define _GLIBCXX_FORWARD(_Tp, __val) std::forward<_Tp>(__val)
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#else
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#define _GLIBCXX_FWDREF(_Tp) const _Tp&
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#define _GLIBCXX_MOVE(__val) (__val)
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#define _GLIBCXX_FORWARD(_Tp, __val) (__val)
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#endif
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/**
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* @addtogroup utilities
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* @{
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*/
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/**
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* @brief Swaps two values.
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* @param __a A thing of arbitrary type.
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* @param __b Another thing of arbitrary type.
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* @return Nothing.
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*/
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template<typename _Tp>
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_GLIBCXX20_CONSTEXPR
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inline
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#if __cplusplus >= 201103L
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typename enable_if<__and_<__not_<__is_tuple_like<_Tp>>,
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is_move_constructible<_Tp>,
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is_move_assignable<_Tp>>::value>::type
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#else
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void
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#endif
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swap(_Tp& __a, _Tp& __b)
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_GLIBCXX_NOEXCEPT_IF(__and_<is_nothrow_move_constructible<_Tp>,
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is_nothrow_move_assignable<_Tp>>::value)
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{
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#if __cplusplus < 201103L
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// concept requirements
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__glibcxx_function_requires(_SGIAssignableConcept<_Tp>)
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#endif
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_Tp __tmp = _GLIBCXX_MOVE(__a);
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__a = _GLIBCXX_MOVE(__b);
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__b = _GLIBCXX_MOVE(__tmp);
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}
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// _GLIBCXX_RESOLVE_LIB_DEFECTS
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// DR 809. std::swap should be overloaded for array types.
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/// Swap the contents of two arrays.
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template<typename _Tp, size_t _Nm>
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_GLIBCXX20_CONSTEXPR
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inline
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#if __cplusplus >= 201103L
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typename enable_if<__is_swappable<_Tp>::value>::type
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#else
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void
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#endif
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swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm])
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_GLIBCXX_NOEXCEPT_IF(__is_nothrow_swappable<_Tp>::value)
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{
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for (size_t __n = 0; __n < _Nm; ++__n)
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swap(__a[__n], __b[__n]);
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}
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/// @} group utilities
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_GLIBCXX_END_NAMESPACE_VERSION
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} // namespace
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#endif /* _MOVE_H */
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