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libstdc++: Use correct argument type for __use_alloc [PR 96803]

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The _Tuple_impl constructor for allocator-extended construction from a
different tuple type uses the _Tuple_impl's own _Head type in the
__use_alloc test. That is incorrect, because the argument tuple could
have a different type. Using the wrong type might select the
leading-allocator convention when it should use the trailing-allocator
convention, or vice versa.

libstdc++-v3/ChangeLog:

	PR libstdc++/96803
	* include/std/tuple
	(_Tuple_impl(allocator_arg_t, Alloc, const _Tuple_impl<U...>&)):
	Replace parameter pack with a type parameter and a pack and pass
	the first type to __use_alloc.
	* testsuite/20_util/tuple/cons/96803.cc: New test.
This commit is contained in:
Jonathan Wakely 2020-08-26 19:32:30 +01:00
parent 0c5df67ffc
commit 5494edae83
2 changed files with 46 additions and 5 deletions
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10
libstdc++-v3/include/std/tuple
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@ -338,14 +338,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_Base(__use_alloc<_Head, _Alloc, _Head>(__a),
std::forward<_Head>(_M_head(__in))) { }
template<typename _Alloc, typename... _UElements>
template<typename _Alloc, typename _UHead, typename... _UTails>
_GLIBCXX20_CONSTEXPR
_Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
const _Tuple_impl<_Idx, _UElements...>& __in)
const _Tuple_impl<_Idx, _UHead, _UTails...>& __in)
: _Inherited(__tag, __a,
_Tuple_impl<_Idx, _UElements...>::_M_tail(__in)),
_Base(__use_alloc<_Head, _Alloc, _Head>(__a),
_Tuple_impl<_Idx, _UElements...>::_M_head(__in)) { }
_Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in)),
_Base(__use_alloc<_Head, _Alloc, _UHead>(__a),
_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in)) { }
template<typename _Alloc, typename _UHead, typename... _UTails>
_GLIBCXX20_CONSTEXPR

41
libstdc++-v3/testsuite/20_util/tuple/cons/96803.cc Normal file
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@ -0,0 +1,41 @@
// Copyright (C) 2020 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-do compile { target c++11 } }
#include <tuple>
#include <memory>
struct X
{
using allocator_type = std::allocator<int>;
X(X&&) { }
X(std::allocator_arg_t, const allocator_type&, X&&) { }
explicit X(int) { }
explicit X(int, allocator_type) { }
};
void
test01()
{
// PR libstdc++/96803
// std::tuple chooses wrong constructor for uses-allocator construction
std::tuple<int> o;
std::tuple<X> nok(std::allocator_arg, std::allocator<int>(), o);
}