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

[Ken Matsui <kmatsui@cs.washington.edu>]

I see. Thank you!

On Mon, Mar 20, 2023 at 12:26 AM Xi Ruoyao <xry111@xry111.site> wrote:
>
> You need to CC libstdc++@gcc.gnu.org for any patches touching libstdc++.
>
> On Sat, 2023-03-18 at 21:21 -0700, Ken Matsui via Gcc-patches wrote:
> > libstdc++-v3/ChangeLog:
> >
> > * include/std/type_traits (is_reference): Use __is_reference built-in
> > trait.
>
> Bad ChangeLog format.  You should have a tab (not 4 or 8 spaces, nor
> nothing) to indent the ChangeLog content.
>
> Is there any benefit to use a builtin, instead of the existing
> implementation?  I can see no but maybe I'm stupid.
>
> > ---
> > diff --git a/libstdc++-v3/include/std/type_traits
> > b/libstdc++-v3/include/std/type_traits
>
> The patch fails to apply.  It seems because your mail client inserted an
> additional newline before "b/".  Try to use git-send-email or configure
> the mail client properly.
>
> > index 2bd607a8b8f..18408d8ceb6 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 integral_constant<bool, __is_reference(_Tp)>
>
> If a patch depends on another patch not applied yet, sent them in a
> series.  Or people are puzzled because when this patch is applied alone,
> the code fails to build.
>
> > +    { };
> > +#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>
>
> --
> Xi Ruoyao <xry111@xry111.site>
> School of Aerospace Science and Technology, Xidian University