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| author | redi <redi@138bc75d-0d04-0410-961f-82ee72b054a4> | 2015-04-28 12:07:34 +0000 |
|---|---|---|
| committer | redi <redi@138bc75d-0d04-0410-961f-82ee72b054a4> | 2015-04-28 12:07:34 +0000 |
| commit | 75907ee68dacc603748554e9146ab265a4e9c407 (patch) | |
| tree | dd9f52ae38525003368a15ba8e5e7dcb37385e62 /libstdc++-v3 | |
| parent | 9e37e96e529021aea539d2f2be18be87442235dc (diff) | |
| download | gcc-75907ee68dacc603748554e9146ab265a4e9c407.tar.gz | |
* include/std/type_traits (void_t): Add.
* testsuite/20_util/void_t/1.cc: New.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@222522 138bc75d-0d04-0410-961f-82ee72b054a4
Diffstat (limited to 'libstdc++-v3')
| -rw-r--r-- | libstdc++-v3/ChangeLog | 5 | ||||
| -rw-r--r-- | libstdc++-v3/include/std/type_traits | 6 | ||||
| -rw-r--r-- | libstdc++-v3/testsuite/20_util/void_t/1.cc | 45 |
3 files changed, 56 insertions, 0 deletions
diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog index c25f2a239c4..7dfb96e40f8 100644 --- a/libstdc++-v3/ChangeLog +++ b/libstdc++-v3/ChangeLog @@ -1,3 +1,8 @@ +2015-04-28 Jonathan Wakely <jwakely@redhat.com> + + * include/std/type_traits (void_t): Add. + * testsuite/20_util/void_t/1.cc: New. + 2015-04-28 Tim Shen <timshen@google.com> * include/bits/regex.tcc: Handle regex_constants::__polynomial. diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits index 03e198acd08..3ed1a7b5a0a 100644 --- a/libstdc++-v3/include/std/type_traits +++ b/libstdc++-v3/include/std/type_traits @@ -2406,6 +2406,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION template<typename...> using __void_t = void; +#if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11 +#define __cpp_lib_void_t 201411 + /// A metafunction that always yields void, used for detecting valid types. + template<typename...> using void_t = void; +#endif + /// @} group metaprogramming /** diff --git a/libstdc++-v3/testsuite/20_util/void_t/1.cc b/libstdc++-v3/testsuite/20_util/void_t/1.cc new file mode 100644 index 00000000000..fe5c507580c --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/void_t/1.cc @@ -0,0 +1,45 @@ +// Copyright (C) 2015 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++1z" } +// { dg-do compile } + +#include <type_traits> + +#ifndef __cpp_lib_void_t +# error "Feature-test macro for void_t missing" +#elif __cpp_lib_void_t != 201411 +# error "Feature-test macro for void_t has wrong value" +#endif + +static_assert( std::is_same<std::void_t<int, long, double>, void>::value, + "void_t is a synonym for void" ); + +struct X { }; +X operator+(const X& x) { return x; } + +template<typename T, typename U = std::void_t<>> +struct has_unary_plus +: std::false_type +{ }; + +template<typename T> +struct has_unary_plus<T, std::void_t<decltype(+std::declval<X>())>> +: std::true_type +{ }; + +static_assert( has_unary_plus<X>::value, "void_t detects valid expressions" ); |