linux-kernel - Re: [PATCH] utilize _Static_assert() for BUILD_BUG

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 05 Nov 2012 12:49:11 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Jan Beulich <JBeulich@...e.com>, akpm@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] utilize _Static_assert() for BUILD_BUG_ON() when the compiler supports it

Jan Beulich <JBeulich@...e.com> writes:
> This makes the resulting diagnostics quite a bit more useful.
>
> Signed-off-by: Jan Beulich <jbeulich@...e.com>

Nice.  I'm a bit disappointed we can't just treat _Static_assert() as
void, like:

#define BUILD_BUG_ON_ZERO(e) (_Static_assert(!(e), "!(" #e ")"), 0)

> @@ -54,6 +61,15 @@ struct pt_regs;
>   */
>  #ifndef __OPTIMIZE__
>  #define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))
> +#elif __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
> +#define __build_bug_on_failed(n) __build_bug_on_##n##_failed
> +#define _BUILD_BUG_ON(n, condition)				\
> +	do {							\
> +		extern void __compiletime_error(#condition)	\
> +		__build_bug_on_failed(n)(void);			\
> +		if (condition) __build_bug_on_failed(n)();	\
> +	} while(0)
> +#define BUILD_BUG_ON(condition...) _BUILD_BUG_ON(__COUNTER__, ##condition)
>  #else
>  extern int __build_bug_on_failed;
>  #define BUILD_BUG_ON(condition)					\

Why does this depend on gcc version?  Looks like residue from an attempt
to use _Static_assert here?

Thanks,
Rusty.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/