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

[Jonathan Wakely]

On Mon, 20 Mar 2023, 07:32 Ken Matsui via Libstdc++, <libstdc++@gcc.gnu.org>
wrote:

> 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.
>

The changelog entry says is_reference but the patch is for remove_pointer.


>
> > ---
> > 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; };
>

The helper doesn't need to be defined for the case where we don't use it.


>
> >    /// 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
>