Re: [PATCH] libstdc++: Use _GLIBCXX_USE_BUILTIN_TRAIT for is_same

[Jonathan Wakely <jwakely@redhat.com>]

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On Fri, 9 Feb 2024 at 16:02, Patrick Palka <ppalka@redhat.com> wrote:

> On Thu, 8 Feb 2024, Ken Matsui wrote:
>
> > Since is_same has a fallback native implementation, and
> > _GLIBCXX_HAVE_BUILTIN_IS_SAME does not support toggling which
> > implementation to use, we remove the _GLIBCXX_HAVE_BUILTIN_IS_SAME
> > definition and use _GLIBCXX_USE_BUILTIN_TRAIT instead.
> >
> > libstdc++-v3/ChangeLog:
> >
> >       * include/bits/c++config (_GLIBCXX_HAVE_BUILTIN_IS_SAME):
> >       Removed.
> >       * include/std/type_traits (is_same): Use
> >       _GLIBCXX_USE_BUILTIN_TRAIT instead of
> >       _GLIBCXX_HAVE_BUILTIN_IS_SAME.
> >       (is_same_v): Likewise.
>
> LGTM
>

Me too, OK for trunk, thanks.

+Reviewed-by: Jonathan Wakely <jwakely@redhat.com>



>
> >
> > Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
> > ---
> >  libstdc++-v3/include/bits/c++config  | 4 ----
> >  libstdc++-v3/include/std/type_traits | 9 +++++----
> >  2 files changed, 5 insertions(+), 8 deletions(-)
> >
> > diff --git a/libstdc++-v3/include/bits/c++config
> b/libstdc++-v3/include/bits/c++config
> > index ad07ce92d5f..b57e3f338e9 100644
> > --- a/libstdc++-v3/include/bits/c++config
> > +++ b/libstdc++-v3/include/bits/c++config
> > @@ -845,10 +845,6 @@ namespace __gnu_cxx
> >  # define _GLIBCXX_HAVE_BUILTIN_IS_AGGREGATE 1
> >  #endif
> >
> > -#if _GLIBCXX_HAS_BUILTIN(__is_same)
> > -#  define _GLIBCXX_HAVE_BUILTIN_IS_SAME 1
> > -#endif
> > -
> >  #if _GLIBCXX_HAS_BUILTIN(__builtin_launder)
> >  # define _GLIBCXX_HAVE_BUILTIN_LAUNDER 1
> >  #endif
> > diff --git a/libstdc++-v3/include/std/type_traits
> b/libstdc++-v3/include/std/type_traits
> > index a9bb2806ca9..21402fd8c13 100644
> > --- a/libstdc++-v3/include/std/type_traits
> > +++ b/libstdc++-v3/include/std/type_traits
> > @@ -1470,16 +1470,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >    // Type relations.
> >
> >    /// is_same
> > +#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_same)
> >    template<typename _Tp, typename _Up>
> >      struct is_same
> > -#ifdef _GLIBCXX_HAVE_BUILTIN_IS_SAME
> >      : public __bool_constant<__is_same(_Tp, _Up)>
> > +    { };
> >  #else
> > +  template<typename _Tp, typename _Up>
> > +    struct is_same
> >      : public false_type
> > -#endif
> >      { };
> >
> > -#ifndef _GLIBCXX_HAVE_BUILTIN_IS_SAME
> >    template<typename _Tp>
> >      struct is_same<_Tp, _Tp>
> >      : public true_type
> > @@ -3496,7 +3497,7 @@ template <typename _Tp>
> >  template <typename _Tp, unsigned _Idx>
> >    inline constexpr size_t extent_v<_Tp[], _Idx> = extent_v<_Tp, _Idx -
> 1>;
> >
> > -#ifdef _GLIBCXX_HAVE_BUILTIN_IS_SAME
> > +#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_same)
> >  template <typename _Tp, typename _Up>
> >    inline constexpr bool is_same_v = __is_same(_Tp, _Up);
> >  #else
> > --
> > 2.43.0
> >
> >
>
>