By using the built-in we don't need to match a partial specialization
for std::is_same and don't need to instantiate std::is_same at all for
uses of std::is_same_v.
* include/std/type_traits (is_same): Replace partial specialization
by using __is_same_as built-in in primary template.
(is_same_v): Use __is_same_as built-in instead of instantiating the
is_same trait.
Tested x86_64-linux, committed to trunk.
commit ee208e530893aeb12b6a9edb1563a4e8ecaea887
Author: Jonathan Wakely <[email protected]>
Date: Wed Sep 11 21:23:31 2019 +0100
Use __is_same_as for std::is_same and std::is_same_v
By using the built-in we don't need to match a partial specialization
for std::is_same and don't need to instantiate std::is_same at all for
uses of std::is_same_v.
* include/std/type_traits (is_same): Replace partial specialization
by using __is_same_as built-in in primary template.
(is_same_v): Use __is_same_as built-in instead of instantiating the
is_same trait.
diff --git a/libstdc++-v3/include/std/type_traits
b/libstdc++-v3/include/std/type_traits
index dc8a019324d..4de5daa9f06 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -1388,13 +1388,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// Type relations.
/// is_same
- template<typename, typename>
+ template<typename _Tp, typename _Up>
struct is_same
- : public false_type { };
-
- template<typename _Tp>
- struct is_same<_Tp, _Tp>
- : public true_type { };
+ : public integral_constant<bool, __is_same_as(_Tp, _Up)>
+ { };
/// is_base_of
template<typename _Base, typename _Derived>
@@ -3158,7 +3155,7 @@ template <typename _Tp>
template <typename _Tp, unsigned _Idx = 0>
inline constexpr size_t extent_v = extent<_Tp, _Idx>::value;
template <typename _Tp, typename _Up>
- inline constexpr bool is_same_v = is_same<_Tp, _Up>::value;
+ inline constexpr bool is_same_v = __is_same_as(_Tp, _Up);
template <typename _Base, typename _Derived>
inline constexpr bool is_base_of_v = is_base_of<_Base, _Derived>::value;
template <typename _From, typename _To>
