Re: [PATCH v2] libstdc++: Define _GLIBCXX_HAS_BUILTIN_TRAIT

[Patrick Palka <ppalka@redhat.com>]

On Wed, Jul 19, 2023 at 3:33 PM Ken Matsui via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> This patch defines _GLIBCXX_HAS_BUILTIN_TRAIT macro, which will be used
> as a flag to toggle the use of built-in traits in the type_traits header
> through _GLIBCXX_NO_BUILTIN_TRAITS macro, without needing to modify the
> source code.

LGTM!

>
> libstdc++-v3/ChangeLog:
>
>         * include/bits/c++config (_GLIBCXX_HAS_BUILTIN_TRAIT): Define.
>         (_GLIBCXX_HAS_BUILTIN): Keep defined.
>
> Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
> ---
>  libstdc++-v3/include/bits/c++config | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/libstdc++-v3/include/bits/c++config b/libstdc++-v3/include/bits/c++config
> index dd47f274d5f..984985d6fff 100644
> --- a/libstdc++-v3/include/bits/c++config
> +++ b/libstdc++-v3/include/bits/c++config
> @@ -854,7 +854,15 @@ namespace __gnu_cxx
>  # define _GLIBCXX_HAVE_BUILTIN_LAUNDER 1
>  #endif
>
> -#undef _GLIBCXX_HAS_BUILTIN
> +// Returns 1 if _GLIBCXX_NO_BUILTIN_TRAITS is not defined and the compiler
> +// has a corresponding built-in type trait, 0 otherwise.
> +// _GLIBCXX_NO_BUILTIN_TRAITS can be defined to disable the use of built-in
> +// traits.
> +#ifndef _GLIBCXX_NO_BUILTIN_TRAITS
> +# define _GLIBCXX_HAS_BUILTIN_TRAIT(BT) _GLIBCXX_HAS_BUILTIN(BT)
> +#else
> +# define _GLIBCXX_HAS_BUILTIN_TRAIT(BT) 0
> +#endif
>
>  // Mark code that should be ignored by the compiler, but seen by Doxygen.
>  #define _GLIBCXX_DOXYGEN_ONLY(X)
> --
> 2.41.0
>