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Commit b7dbc672 by Jonathan Wakely Committed by Jonathan Wakely
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DR 2586 fix value category in uses-allocator checks 

Because uses-allocator construction is invariably done with a const
lvalue the __uses_alloc helper should use a const lvalue for the
is_constructible checks. Otherwise, it can detect that the type can be
constructed from an rvalue, and then an error happens when a const
lvalue is passed to the constructor instead.

Prior to LWG DR 2586 scoped_allocator_adaptor incorrectly used an rvalue
type in the is_constructible check and then used a non-const lvalue for
the actual construction. The other components using uses-allocator
construction (tuple and polymorphic_allocator) have always done so with
a const lvalue allocator, although the use of __use_alloc in our
implementation meant they behaved the same as scoped_allocator_adaptor
and incorrectly used rvalues for the is_constructible checks.

In C++20 the P0591R4 changes mean that all uses-allocator construction
is defined in terms of the new uses_allocator_construction_args
functions, which always use a const lvalue allocator.

The changes in this patch ensure that the __use_alloc helper correctly
matches the requirements in the standard, consistently using a const
lvalue allocator for the is_constructible checks and the actual
constructor arguments.

	* doc/xml/manual/intro.xml: Document LWG 2586 status.
	* include/bits/uses_allocator.h (__uses_alloc): Use const lvalue
	allocator type in is_constructible checks.
	* testsuite/20_util/scoped_allocator/69293_neg.cc: Adjust dg-error.
	* testsuite/20_util/scoped_allocator/dr2586.cc: New test.
	* testsuite/20_util/tuple/cons/allocators.cc: Add test using
	problematic type from LWG 2586 discussion.
	* testsuite/20_util/uses_allocator/69293_neg.cc: Adjust dg-error.
	* testsuite/20_util/uses_allocator/cons_neg.cc: Likewise.

From-SVN: r268882
parent 6461bdc4
Showing with 76 additions and 7 deletions
libstdc++-v3/ChangeLog
2019-02-14 Jonathan Wakely <jwakely@redhat.com>
* doc/xml/manual/intro.xml: Document LWG 2586 status.
* include/bits/uses_allocator.h (__uses_alloc): Use const lvalue
allocator type in is_constructible checks.
* testsuite/20_util/scoped_allocator/69293_neg.cc: Adjust dg-error.
* testsuite/20_util/scoped_allocator/dr2586.cc: New test.
* testsuite/20_util/tuple/cons/allocators.cc: Add test using
problematic type from LWG 2586 discussion.
* testsuite/20_util/uses_allocator/69293_neg.cc: Adjust dg-error.
* testsuite/20_util/uses_allocator/cons_neg.cc: Likewise.
* configure.ac: Check for C11 timespec_get function.
* crossconfig.m4 (freebsd, linux, gnu, cygwin, solaris, netbsd)
(openbsd): Likewise
......
libstdc++-v3/doc/xml/manual/intro.xml
......@@ -1142,6 +1142,14 @@ requirements of the license of GCC.
<listitem><para>Add new constructor.
</para></listitem></varlistentry>
<varlistentry xml:id="manual.bugs.dr2586"><term><link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="&DR;#2586">2586</link>:
<emphasis>Wrong value category used in <code>scoped_allocator_adaptor::construct()</code>
</emphasis>
</term>
<listitem><para>Change internal helper for uses-allocator construction
to always check using const lvalue allocators.
</para></listitem></varlistentry>
<varlistentry xml:id="manual.bugs.dr2684"><term><link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="&DR;#2684">2684</link>:
<emphasis><code>priority_queue</code> lacking comparator typedef
</emphasis>
......
libstdc++-v3/include/bits/uses_allocator.h
......@@ -87,14 +87,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _Tp, typename _Alloc, typename... _Args>
struct __uses_alloc<true, _Tp, _Alloc, _Args...>
: conditional<
is_constructible<_Tp, allocator_arg_t, _Alloc, _Args...>::value,
is_constructible<_Tp, allocator_arg_t, const _Alloc&, _Args...>::value,
__uses_alloc1<_Alloc>,
__uses_alloc2<_Alloc>>::type
{
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 2586. Wrong value category used in scoped_allocator_adaptor::construct
static_assert(__or_<
is_constructible<_Tp, allocator_arg_t, _Alloc, _Args...>,
is_constructible<_Tp, _Args..., _Alloc>>::value, "construction with"
" an allocator must be possible if uses_allocator is true");
is_constructible<_Tp, allocator_arg_t, const _Alloc&, _Args...>,
is_constructible<_Tp, _Args..., const _Alloc&>>::value,
"construction with an allocator must be possible"
" if uses_allocator is true");
};
template<typename _Tp, typename _Alloc, typename... _Args>
......
libstdc++-v3/testsuite/20_util/scoped_allocator/69293_neg.cc
......@@ -46,5 +46,5 @@ test01()
scoped_alloc sa;
auto p = sa.allocate(1);
sa.construct(p); // this is required to be ill-formed
// { dg-error "static assertion failed" "" { target *-*-* } 96 }
// { dg-error "failed: .* uses_allocator is true" "" { target *-*-* } 0 }
}
libstdc++-v3/testsuite/20_util/scoped_allocator/dr2586.cc 0 → 100644
// Copyright (C) 2019 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 <memory>
#include <scoped_allocator>
// DR 2586. Wrong value category used in scoped_allocator_adaptor::construct()
struct X {
using allocator_type = std::allocator<X>;
X(std::allocator_arg_t, allocator_type&&) { }
X(const allocator_type&) { }
};
int main() {
std::scoped_allocator_adaptor<std::allocator<X>> sa;
sa.construct(sa.allocate(1));
}
libstdc++-v3/testsuite/20_util/tuple/cons/allocators.cc
......@@ -181,9 +181,23 @@ void test02()
test_type empty = make_tuple();
}
void test03()
{
struct dr2586
{
using allocator_type = std::allocator<int>;
dr2586(std::allocator_arg_t, allocator_type&&) { }
dr2586(const allocator_type&) { }
};
const dr2586::allocator_type a;
std::tuple<dr2586> t{std::allocator_arg, a};
}
int main()
{
test01();
test02();
test03();
return 0;
}
libstdc++-v3/testsuite/20_util/uses_allocator/69293_neg.cc
......@@ -44,5 +44,5 @@ test01()
{
alloc_type a;
std::tuple<X> t(std::allocator_arg, a); // this is required to be ill-formed
// { dg-error "static assertion failed" "" { target *-*-* } 96 }
// { dg-error "failed: .* uses_allocator is true" "" { target *-*-* } 0 }
}
libstdc++-v3/testsuite/20_util/uses_allocator/cons_neg.cc
......@@ -43,4 +43,4 @@ void test01()
tuple<Type> t(allocator_arg, a, 1);
}
// { dg-error "static assertion failed" "" { target *-*-* } 96 }
// { dg-error "failed: .* uses_allocator is true" "" { target *-*-* } 0 }
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