[PATCH] libstdc++: use new built-in trait __remove_pointer

[Ken Matsui]

CCing libstdc++@gcc.gnu.org.

On Sun, Mar 19, 2023 at 7:53 PM Ken Matsui <kmatsui@cs.washington.edu> wrote:
>
> libstdc++-v3/ChangeLog:
>
> * include/std/type_traits (is_reference): Use __remove_pointer built-in trait.
>
> ---
> diff --git a/libstdc++-v3/include/std/type_traits
> b/libstdc++-v3/include/std/type_traits
> index 2bd607a8b8f..cba98091aad 100644
> --- a/libstdc++-v3/include/std/type_traits
> +++ b/libstdc++-v3/include/std/type_traits
> @@ -2025,17 +2025,23 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>
>    template<typename _Tp, typename>
>      struct __remove_pointer_helper
> -    { typedef _Tp     type; };
> +    { using type = _Tp; };
>
>    template<typename _Tp, typename _Up>
>      struct __remove_pointer_helper<_Tp, _Up*>
> -    { typedef _Up     type; };
> +    { using type = _Up; };
>
>    /// remove_pointer
> +#if __has_builtin(__remove_pointer)
> +  template<typename _Tp>
> +    struct remove_pointer
> +    { using type = __remove_pointer(_Tp); };
> +#else
>    template<typename _Tp>
>      struct remove_pointer
>      : public __remove_pointer_helper<_Tp, __remove_cv_t<_Tp>>
>      { };
> +#endif
>
>    template<typename _Tp, typename = void>
>      struct __add_pointer_helper