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
>
> Signed-off-by: Ken Matsui <kmat...@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
>
>
