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Define std::as_const

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* include/std/utility (as_const): Define.
	* testsuite/20_util/as_const/1.cc: New test.
	* testsuite/20_util/as_const/rvalue_neg.cc: New test.

From-SVN: r239090
This commit is contained in:
Jonathan Wakely 2016-08-03 19:11:23 +01:00 committed by Jonathan Wakely
parent b7dabce5f3
commit 32eaac9c91
4 changed files with 69 additions and 0 deletions
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4
libstdc++-v3/ChangeLog
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@ -1,5 +1,9 @@
2016-08-03 Jonathan Wakely <jwakely@redhat.com>
* include/std/utility (as_const): Define.
* testsuite/20_util/as_const/1.cc: New test.
* testsuite/20_util/as_const/rvalue_neg.cc: New test.
* include/bits/shared_ptr.h (owner_less): Add default template
argument.
* include/bits/shared_ptr_base.h (_Sp_owner_less<void, void>): Define

7
libstdc++-v3/include/std/utility
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@ -356,6 +356,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template <size_t _Idx>
in_place_tag in_place(__in_place_index<_Idx>*) {terminate();}
#define __cpp_lib_as_const 201510
template<typename _Tp>
constexpr add_const_t<_Tp>& as_const(_Tp& __t) noexcept { return __t; }
template<typename _Tp>
void as_const(const _Tp&&) = delete;
#endif
_GLIBCXX_END_NAMESPACE_VERSION

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libstdc++-v3/testsuite/20_util/as_const/1.cc Normal file
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@ -0,0 +1,30 @@
// Copyright (C) 2016 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.
// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING3. If not see
// <http://www.gnu.org/licenses/>.
// { dg-options "-std=gnu++17" }
// { dg-do compile }
#include <utility>
#if __cpp_lib_as_const != 201510
# error "__cpp_lib_as_const != 201510"
#endif
int i;
constexpr auto& ci = std::as_const(i);
static_assert( &i == &ci );
static_assert( std::is_same_v<decltype(std::as_const(i)), const int&> );

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libstdc++-v3/testsuite/20_util/as_const/rvalue_neg.cc Normal file
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// Copyright (C) 2016 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.
// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING3. If not see
// <http://www.gnu.org/licenses/>.
// { dg-options "-std=gnu++17" }
// { dg-do compile }
#include <utility>
void test01()
{
int i = 0;
std::as_const(std::move(i)); // { dg-error "deleted function" }
std::as_const(0); // { dg-error "deleted function" }
}