The PR is actually due to a defect in the standard, which I reported today. The reporter said we're missing a check for is_constructible<T, Args..., inner_allocator_type> that would ensure we go to bullet (9.4) and make the example in the PR ill-formed. I didn't add that check because it's redundant, we don't need to check is_constructible we can just try the construction and if it fails the program is ill-formed anyway.
However, due to the defect in the standard the example in the PR *should* be ill-formed, but isn't. This patch adds a static assertion making it ill-formed. It would be ill-formed anyway once the defect is resolved and we implement the resolution, but with the static assertion we give a better diagnostic, both for scoped_allocator_adaptor and for ill-formed uses of allocators with std::tuple. Tested powerpc64le-linux, committed to trunk.
commit ccd75a6477a0be335d8d38fcbcd6047cebaee096 Author: Jonathan Wakely <jwak...@redhat.com> Date: Fri Jan 15 19:48:25 2016 +0000 Use static assertion for uses-allocator construction PR libstdc++/69293 * include/bits/uses_allocator.h (__uses_alloc<true, ...>): Add static assertion that type is constructible from the arguments. * testsuite/20_util/scoped_allocator/69293_neg.cc: New. * testsuite/20_util/uses_allocator/69293_neg.cc: New. * testsuite/20_util/uses_allocator/cons_neg.cc: Adjust dg-error. diff --git a/libstdc++-v3/include/bits/uses_allocator.h b/libstdc++-v3/include/bits/uses_allocator.h index 70ba007..b1ff58a 100644 --- a/libstdc++-v3/include/bits/uses_allocator.h +++ b/libstdc++-v3/include/bits/uses_allocator.h @@ -85,7 +85,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION is_constructible<_Tp, allocator_arg_t, _Alloc, _Args...>::value, __uses_alloc1<_Alloc>, __uses_alloc2<_Alloc>>::type - { }; + { + 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"); + }; template<typename _Tp, typename _Alloc, typename... _Args> struct __uses_alloc<false, _Tp, _Alloc, _Args...> diff --git a/libstdc++-v3/testsuite/20_util/scoped_allocator/69293_neg.cc b/libstdc++-v3/testsuite/20_util/scoped_allocator/69293_neg.cc new file mode 100644 index 0000000..f3b2d87 --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/scoped_allocator/69293_neg.cc @@ -0,0 +1,51 @@ +// 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++11" } +// { dg-do compile } + +// PR libstdc++/69293 + +#include <scoped_allocator> +#include <memory> + +using std::allocator; +using std::allocator_arg_t; +using std::uses_allocator; +using std::scoped_allocator_adaptor; +using std::is_constructible; + +struct X +{ + using allocator_type = allocator<int>; +}; + +using scoped_alloc = scoped_allocator_adaptor<allocator<X>, X::allocator_type>; +using inner_alloc_type = scoped_alloc::inner_allocator_type; + +static_assert(uses_allocator<X, inner_alloc_type>{}, ""); +static_assert(!is_constructible<X, allocator_arg_t, inner_alloc_type>{}, ""); +static_assert(!is_constructible<X, inner_alloc_type>{}, ""); + +void +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 *-*-* } 89 } +} diff --git a/libstdc++-v3/testsuite/20_util/uses_allocator/69293_neg.cc b/libstdc++-v3/testsuite/20_util/uses_allocator/69293_neg.cc new file mode 100644 index 0000000..19417fc --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/uses_allocator/69293_neg.cc @@ -0,0 +1,49 @@ +// 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++11" } +// { dg-do compile } + +// PR libstdc++/69293 + +#include <tuple> +#include <memory> + +using std::allocator; +using std::allocator_arg_t; +using std::uses_allocator; +using std::tuple; +using std::is_constructible; + +struct X +{ + using allocator_type = allocator<int>; +}; + +using alloc_type = X::allocator_type; + +static_assert(uses_allocator<X, alloc_type>{}, ""); +static_assert(!is_constructible<X, allocator_arg_t, alloc_type>{}, ""); +static_assert(!is_constructible<X, alloc_type>{}, ""); + +void +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 *-*-* } 89 } +} diff --git a/libstdc++-v3/testsuite/20_util/uses_allocator/cons_neg.cc b/libstdc++-v3/testsuite/20_util/uses_allocator/cons_neg.cc index 00f96d6..b3df4ae 100644 --- a/libstdc++-v3/testsuite/20_util/uses_allocator/cons_neg.cc +++ b/libstdc++-v3/testsuite/20_util/uses_allocator/cons_neg.cc @@ -44,4 +44,4 @@ void test01() tuple<Type> t(allocator_arg, a, 1); } -// { dg-error "no matching function" "" { target *-*-* } 92 } +// { dg-error "static assertion failed" "" { target *-*-* } 89 }