Re: [PATCH] libstdc++: Use __bool_constant entirely

[Jonathan Wakely <jwakely@redhat.com>]

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On Sat, 15 Jul 2023 at 04:02, Ken Matsui via Libstdc++ <
libstdc++@gcc.gnu.org> wrote:

> This patch uses __bool_constant entirely instead of integral_constant<bool>
> in the type_traits header, specifically for true_type, false_type,
> and bool_constant.
>
> libstdc++-v3/ChangeLog:
>
>         * include/std/type_traits (true_type): Use __bool_constant
>         instead.
>         (false_type): Likewise.
>         (bool_constant): Likewise.
>
> Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
> ---
>  libstdc++-v3/include/std/type_traits | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/libstdc++-v3/include/std/type_traits
> b/libstdc++-v3/include/std/type_traits
> index 9f086992ebc..7dc5791a7c5 100644
> --- a/libstdc++-v3/include/std/type_traits
> +++ b/libstdc++-v3/include/std/type_traits
> @@ -78,24 +78,24 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>      constexpr _Tp integral_constant<_Tp, __v>::value;
>  #endif
>
> -  /// The type used as a compile-time boolean with true value.
> -  using true_type =  integral_constant<bool, true>;
> -
> -  /// The type used as a compile-time boolean with false value.
> -  using false_type = integral_constant<bool, false>;
> -
>    /// @cond undocumented
>    /// bool_constant for C++11
>    template<bool __v>
>      using __bool_constant = integral_constant<bool, __v>;
>    /// @endcond
>
> +  /// The type used as a compile-time boolean with true value.
> +  using true_type =  __bool_constant<true>;
> +
> +  /// The type used as a compile-time boolean with false value.
> +  using false_type = __bool_constant<false>;
> +
>  #if __cplusplus >= 201703L
>  # define __cpp_lib_bool_constant 201505L
>    /// Alias template for compile-time boolean constant types.
>    /// @since C++17
>    template<bool __v>
> -    using bool_constant = integral_constant<bool, __v>;
> +    using bool_constant = __bool_constant<__v>;
>  #endif
>
>    // Metaprogramming helper types.
>
>
This seems a bit pointless IMHO, but I suppose it makes things more
consistent.

OK for trunk.