summaryrefslogtreecommitdiff
path: root/libstdc++-v3
diff options
context:
space:
mode:
authorredi <redi@138bc75d-0d04-0410-961f-82ee72b054a4>2015-04-28 12:07:34 +0000
committerredi <redi@138bc75d-0d04-0410-961f-82ee72b054a4>2015-04-28 12:07:34 +0000
commit75907ee68dacc603748554e9146ab265a4e9c407 (patch)
treedd9f52ae38525003368a15ba8e5e7dcb37385e62 /libstdc++-v3
parent9e37e96e529021aea539d2f2be18be87442235dc (diff)
downloadgcc-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/ChangeLog5
-rw-r--r--libstdc++-v3/include/std/type_traits6
-rw-r--r--libstdc++-v3/testsuite/20_util/void_t/1.cc45
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" );