Re: [PATCH] libstdc++ Use _GLIBCXX_USE_BUILTIN_TRAIT

[Patrick Palka <ppalka@redhat.com>]

On Mon, 11 Sep 2023, Ken Matsui via Gcc-patches wrote:

> This patch uses _GLIBCXX_USE_BUILTIN_TRAIT macro instead of __has_builtin in
> the type_traits header for traits that have a corresponding fallback
> non-built-in implementation. This macro supports to toggle the use of built-in
> traits in the type_traits header through _GLIBCXX_DO_NOT_USE_BUILTIN_TRAITS
> macro, without needing to modify the source code.
> 
> libstdc++-v3/ChangeLog:
> 
> 	* include/std/type_traits: Use _GLIBCXX_USE_BUILTIN_TRAIT.

LGTM

> 
> Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
> ---
>  libstdc++-v3/include/std/type_traits | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
> index 677cd934b94..221c809dd6d 100644
> --- a/libstdc++-v3/include/std/type_traits
> +++ b/libstdc++-v3/include/std/type_traits
> @@ -1430,7 +1430,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>      : public __bool_constant<__is_base_of(_Base, _Derived)>
>      { };
>  
> -#if __has_builtin(__is_convertible)
> +#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_convertible)
>    template<typename _From, typename _To>
>      struct is_convertible
>      : public __bool_constant<__is_convertible(_From, _To)>
> @@ -1480,7 +1480,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>  
>  #ifdef __cpp_lib_is_nothrow_convertible // C++ >= 20
>  
> -#if __has_builtin(__is_nothrow_convertible)
> +#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_nothrow_convertible)
>    /// is_nothrow_convertible_v
>    template<typename _From, typename _To>
>      inline constexpr bool is_nothrow_convertible_v
> @@ -1555,7 +1555,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>      { using type = _Tp; };
>  
>    /// remove_cv
> -#if __has_builtin(__remove_cv)
> +#if _GLIBCXX_USE_BUILTIN_TRAIT(__remove_cv)
>    template<typename _Tp>
>      struct remove_cv
>      { using type = __remove_cv(_Tp); };
> @@ -1621,7 +1621,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    // Reference transformations.
>  
>    /// remove_reference
> -#if __has_builtin(__remove_reference)
> +#if _GLIBCXX_USE_BUILTIN_TRAIT(__remove_reference)
>    template<typename _Tp>
>      struct remove_reference
>      { using type = __remove_reference(_Tp); };
> @@ -3427,7 +3427,7 @@ template<typename _Ret, typename _Fn, typename... _Args>
>     * @{
>     */
>  #ifdef __cpp_lib_remove_cvref // C++ >= 20
> -# if __has_builtin(__remove_cvref)
> +# if _GLIBCXX_USE_BUILTIN_TRAIT(__remove_cvref)
>    template<typename _Tp>
>      struct remove_cvref
>      { using type = __remove_cvref(_Tp); };
> -- 
> 2.42.0
> 
>