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Subject: Re: [PATCH v2] newlib: fix build with <gcc-5 versions
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To: Mike Frysinger <vapier@gentoo.org>, newlib@sourceware.org
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On 15/03/2022 03:25, Mike Frysinger wrote:
> __builtin_mul_overflow showed up with gcc-5, so stub it out for older
> versions.
> ---
>   newlib/libc/include/sys/cdefs.h | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/newlib/libc/include/sys/cdefs.h b/newlib/libc/include/sys/cdefs.h
> index da729092185c..e51f7f4b873a 100644
> --- a/newlib/libc/include/sys/cdefs.h
> +++ b/newlib/libc/include/sys/cdefs.h
> @@ -416,6 +416,10 @@
>   #define	__unreachable()	((void)0)
>   #endif
>   
> +#if !__GNUC_PREREQ__(5, 0)
> +#define __builtin_mul_overflow(a, b, size) ({ *(size) = (a) * (b); 0; })

Wouldn't
(*(size) = (a) * (b), 0)

be more portable (avoiding the GNU statement expression extension)?

R.

> +#endif
> +
>   /* XXX: should use `#if __STDC_VERSION__ < 199901'. */
>   #if !__GNUC_PREREQ__(2, 7) && !defined(__INTEL_COMPILER)
>   #define	__func__	NULL