Re: [PATCH v2] ctype.h: remove duplicate isdigit() helper

[Miguel Ojeda]

On Tue, Oct 27, 2020 at 12:57 AM Arnd Bergmann <arnd@xxxxxxxxxx> wrote:
>
> +#ifdef __has_builtin
> +#define has_builtin(x) __has_builtin(x)
> +#else
> +#define has_builtin(x) (0)
> +#endif

Could this be

    #ifndef __has_builtin
    # define __has_builtin(x) 0
    #endif

? i.e. mimicking what we do for `__has_attribute`.

It would also be a nice idea to put a reminder comment like:

    /*
     * __has_builtin is supported on gcc >= 10, clang >= 3 and icc >= 21.
     * In the meantime, to support gcc < 10, we implement __has_builtin
     * by hand.
     */

Cheers,
Miguel