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PR libstdc++/78939 make tuple_size<cv T> depend on tuple_size<T> 

PR libstdc++/78939
	* include/std/utility (tuple_size<cv T>) [__cplusplus > 201402L]:
	Only define partial specializations when tuple_size<T>::value is
	valid.
	* testsuite/20_util/tuple/78939.cc: New.

From-SVN: r247978
This commit is contained in:
Jonathan Wakely 2017-05-12 16:53:19 +01:00 committed by Jonathan Wakely
parent 012d90bd74
commit cf20ff6ff6
3 changed files with 78 additions and 0 deletions
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8
libstdc++-v3/ChangeLog
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@ -1,3 +1,11 @@
2017-05-12 Jonathan Wakely <jwakely@redhat.com>
PR libstdc++/78939
* include/std/utility (tuple_size<cv T>) [__cplusplus > 201402L]:
Only define partial specializations when tuple_size<T>::value is
valid.
* testsuite/20_util/tuple/78939.cc: New.
2017-05-02 Release Manager
* GCC 7.1.0 released.

21
libstdc++-v3/include/std/utility
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@ -89,6 +89,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 2770. tuple_size<const T> specialization is not SFINAE compatible
#if __cplusplus <= 201402L
template<typename _Tp, typename = void>
struct __tuple_size_cv_impl { };
@ -106,6 +108,25 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _Tp>
struct tuple_size<const volatile _Tp> : __tuple_size_cv_impl<_Tp> { };
#else
template<typename _Tp,
typename _Up = typename remove_cv<_Tp>::type,
typename = typename enable_if<is_same<_Tp, _Up>::value>::type,
size_t = tuple_size<_Tp>::value>
using __enable_if_has_tuple_size = _Tp;
template<typename _Tp>
struct tuple_size<const __enable_if_has_tuple_size<_Tp>>
: public tuple_size<_Tp> { };
template<typename _Tp>
struct tuple_size<volatile __enable_if_has_tuple_size<_Tp>>
: public tuple_size<_Tp> { };
template<typename _Tp>
struct tuple_size<const volatile __enable_if_has_tuple_size<_Tp>>
: public tuple_size<_Tp> { };
#endif
/// Gives the type of the ith element of a given tuple type.
template<std::size_t __i, typename _Tp>

49
libstdc++-v3/testsuite/20_util/tuple/78939.cc Normal file
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@ -0,0 +1,49 @@
// Copyright (C) 2017 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 { target c++1z } }
// PR libstdc++/78939
#include <utility>
struct A { int i, j; };
int
test01()
{
A a{};
const auto [i, j] = a;
return i + j;
}
int
test02()
{
A a{};
volatile auto [i, j] = a;
return i + j;
}
int
test03()
{
A a{};
const volatile auto [i, j] = a;
return i + j;
}