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From: Jonathan Wakely <redi@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r12-566] libstdc++: Fix definition of std::remove_cvref_t Date: Thu, 6 May 2021 12:42:12 +0000 (GMT) [thread overview] Message-ID: <20210506124212.07774384640F@sourceware.org> (raw) https://gcc.gnu.org/g:0e79e63026e43ad0577812ffb405dac8fa88af5b commit r12-566-g0e79e63026e43ad0577812ffb405dac8fa88af5b Author: Jonathan Wakely <jwakely@redhat.com> Date: Thu May 6 13:40:53 2021 +0100 libstdc++: Fix definition of std::remove_cvref_t I originally defined std::remove_cvref_t in terms of the internal __remove_cvref_t trait, to avoid instantiating the remove_cvref class template. However, as described in P1715R0 that is observable by users and is thus non-conforming. This defines remove_cvref_t as specified in the standard. libstdc++-v3/ChangeLog: * include/std/type_traits (remove_cvref_t): Define in terms of remove_cvref. * testsuite/20_util/remove_cvref/value.cc: Check alias. Diff: --- libstdc++-v3/include/std/type_traits | 17 +++++++++++++---- libstdc++-v3/testsuite/20_util/remove_cvref/value.cc | 7 +++++++ 2 files changed, 20 insertions(+), 4 deletions(-) diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits index 1f8b57b04a0..eaf06fcb036 100644 --- a/libstdc++-v3/include/std/type_traits +++ b/libstdc++-v3/include/std/type_traits @@ -3223,12 +3223,21 @@ template <typename _From, typename _To> /// Remove references and cv-qualifiers. template<typename _Tp> struct remove_cvref - { - using type = __remove_cvref_t<_Tp>; - }; + : remove_cv<_Tp> + { }; + + template<typename _Tp> + struct remove_cvref<_Tp&> + : remove_cv<_Tp> + { }; + + template<typename _Tp> + struct remove_cvref<_Tp&&> + : remove_cv<_Tp> + { }; template<typename _Tp> - using remove_cvref_t = __remove_cvref_t<_Tp>; + using remove_cvref_t = typename remove_cvref<_Tp>::type; #define __cpp_lib_type_identity 201806L /// Identity metafunction. diff --git a/libstdc++-v3/testsuite/20_util/remove_cvref/value.cc b/libstdc++-v3/testsuite/20_util/remove_cvref/value.cc index d4a28422977..a4f50d433dc 100644 --- a/libstdc++-v3/testsuite/20_util/remove_cvref/value.cc +++ b/libstdc++-v3/testsuite/20_util/remove_cvref/value.cc @@ -48,3 +48,10 @@ void test01() static_assert(is_same<typename remove_cvref<const int(&)()>::type, const int()>::value, ""); } + +// Declare using nested name of class template +template<typename T> T func(typename std::remove_cvref<T>::type); +// Define using alias +template<typename T> T func(std::remove_cvref_t<T> t) { return t; } +// Call must not be ambiguous +int i = func<int>(1);
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