| Message ID | CAH6eHdSmvVwgtpFcoU+faEKy=Eb8G_ea4Yy2RYz1pG2tEh6Tog@mail.gmail.com |
|---|---|
| State | New |
| Headers | show |
On Tue, May 21, 2013 at 09:18:15AM +0100, Jonathan Wakely wrote: > This broke due to some front end changes that disallow forming > function types that return abstract types. std::reference_wrapper > always passes an lvalue reference to __invoke so it's correct to use > an lvalue reference as the result_of's template argument. > > PR libstdc++/57336 > * include/std/functional (__invoke): Do not form function types with > abstract return type. > * testsuite/20_util/reference_wrapper/invoke-3.cc: New. > > Tested x86_64-linux, committed to trunk. > > Jakub, this is a regression against 4.8.0, should it go on the branch too? > The change is small and isolated to code used by std::reference_wrapper. Ok. Jakub
2013/5/21 Jonathan Wakely <jwakely.gcc@gmail.com>: > This broke due to some front end changes that disallow forming > function types that return abstract types. std::reference_wrapper > always passes an lvalue reference to __invoke so it's correct to use > an lvalue reference as the result_of's template argument. I agree. This was http://cplusplus.github.io/LWG/lwg-defects.html#2017 wasn't it? - Daniel
On 21 May 2013 09:24, Daniel Krügler wrote: > 2013/5/21 Jonathan Wakely <jwakely.gcc@gmail.com>: >> This broke due to some front end changes that disallow forming >> function types that return abstract types. std::reference_wrapper >> always passes an lvalue reference to __invoke so it's correct to use >> an lvalue reference as the result_of's template argument. > > I agree. This was > > http://cplusplus.github.io/LWG/lwg-defects.html#2017 > > wasn't it? Ah yes, thanks! I'd fixed the signature in reference_wrapper but not its __invoke() helper. It's fixed on trunk and the 4.8 branch now. > > - Daniel
diff --git a/libstdc++-v3/include/std/functional b/libstdc++-v3/include/std/functional index 44d3fd5..63ba777 100644 --- a/libstdc++-v3/include/std/functional +++ b/libstdc++-v3/include/std/functional @@ -195,7 +195,7 @@ _GLIBCXX_HAS_NESTED_TYPE(result_type) (!is_member_pointer<_Functor>::value && !is_function<_Functor>::value && !is_function<typename remove_pointer<_Functor>::type>::value), - typename result_of<_Functor(_Args&&...)>::type + typename result_of<_Functor&(_Args&&...)>::type >::type __invoke(_Functor& __f, _Args&&... __args) { diff --git a/libstdc++-v3/testsuite/20_util/reference_wrapper/invoke-3.cc b/libstdc++-v3/testsuite/20_util/reference_wrapper/invoke-3.cc new file mode 100644 index 0000000..4291a67 --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/reference_wrapper/invoke-3.cc @@ -0,0 +1,37 @@ +// { dg-options "-std=gnu++11" } +// { dg-do compile } + +// Copyright (C) 2013 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/>. + +// 20.8.3.4 reference_wrapper invocation [refwrap.invoke] +#include <functional> + +struct ABC +{ + virtual bool operator()() const = 0; +}; + +struct Concrete : ABC +{ + virtual bool operator()() const { return true; } +}; + +Concrete c; +ABC& abc = c; + +auto b = std::cref(abc)();
This broke due to some front end changes that disallow forming function types that return abstract types. std::reference_wrapper always passes an lvalue reference to __invoke so it's correct to use an lvalue reference as the result_of's template argument. PR libstdc++/57336 * include/std/functional (__invoke): Do not form function types with abstract return type. * testsuite/20_util/reference_wrapper/invoke-3.cc: New. Tested x86_64-linux, committed to trunk. Jakub, this is a regression against 4.8.0, should it go on the branch too? The change is small and isolated to code used by std::reference_wrapper. commit 4b5557d04acb37fed7686e720ba0af0ed3428c56 Author: Jonathan Wakely <jwakely.gcc@gmail.com> Date: Tue May 21 08:52:16 2013 +0100 PR libstdc++/57336 * include/std/functional (__invoke): Do not form function types with abstract return type. * testsuite/20_util/reference_wrapper/invoke-3.cc: New.