On Sun, 2 Apr 2023, Ken Matsui via Gcc-patches wrote:
> This patch gets std::is_function to dispatch to new built-in trait
> __is_function.
For std::is_function and other predicate-like type traits, I think we also
want to make the corresponding variable template is_function_v directly
use the built-in too.
>
> libstdc++-v3/ChangeLog:
>
> * include/std/type_traits (is_function): Use __is_function built-in
> trait.
>
> Signed-off-by: Ken Matsui <kmat...@cs.washington.edu>
> ---
> libstdc++-v3/include/std/type_traits | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/libstdc++-v3/include/std/type_traits
> b/libstdc++-v3/include/std/type_traits
> index 58a732735c8..9eafd6b16f2 100644
> --- a/libstdc++-v3/include/std/type_traits
> +++ b/libstdc++-v3/include/std/type_traits
> @@ -594,6 +594,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> { };
>
> /// is_function
> +#if __has_builtin(__is_function)
> + template<typename _Tp>
> + struct is_function
> + : public __bool_constant<__is_function(_Tp)>
> + { };
> +#else
> template<typename _Tp>
> struct is_function
> : public __bool_constant<!is_const<const _Tp>::value> { };
> @@ -605,6 +611,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> template<typename _Tp>
> struct is_function<_Tp&&>
> : public false_type { };
> +#endif
>
> #define __cpp_lib_is_null_pointer 201309L
>
> --
> 2.40.0
>
>
