On Sat, 8 Jul 2023 at 06:13, Ken Matsui via Libstdc++
<libstd...@gcc.gnu.org> wrote:
>
> This patch gets std::is_reference to dispatch to new built-in trait
> __is_reference.
>
> libstdc++-v3/ChangeLog:
>
> * include/std/type_traits (is_reference): Use __is_reference built-in
> trait.
> (is_reference_v): Likewise.
>
> Signed-off-by: Ken Matsui <kmat...@gcc.gnu.org>
OK for trunk after the front-end __is_reference is committed.
> ---
> libstdc++-v3/include/std/type_traits | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/libstdc++-v3/include/std/type_traits
> b/libstdc++-v3/include/std/type_traits
> index 0e7a9c9c7f3..2a14df7e5f9 100644
> --- a/libstdc++-v3/include/std/type_traits
> +++ b/libstdc++-v3/include/std/type_traits
> @@ -639,6 +639,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> // Composite type categories.
>
> /// is_reference
> +#if __has_builtin(__is_reference)
> + template<typename _Tp>
> + struct is_reference
> + : public __bool_constant<__is_reference(_Tp)>
> + { };
> +#else
> template<typename _Tp>
> struct is_reference
> : public false_type
> @@ -653,6 +659,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> struct is_reference<_Tp&&>
> : public true_type
> { };
> +#endif
>
> /// is_arithmetic
> template<typename _Tp>
> @@ -3192,12 +3199,19 @@ template <typename _Tp>
> inline constexpr bool is_class_v = __is_class(_Tp);
> template <typename _Tp>
> inline constexpr bool is_function_v = is_function<_Tp>::value;
> +
> +#if __has_builtin(__is_reference)
> +template <typename _Tp>
> + inline constexpr bool is_reference_v = __is_reference(_Tp);
> +#else
> template <typename _Tp>
> inline constexpr bool is_reference_v = false;
> template <typename _Tp>
> inline constexpr bool is_reference_v<_Tp&> = true;
> template <typename _Tp>
> inline constexpr bool is_reference_v<_Tp&&> = true;
> +#endif
> +
> template <typename _Tp>
> inline constexpr bool is_arithmetic_v = is_arithmetic<_Tp>::value;
> template <typename _Tp>
> --
> 2.41.0
>
