linux-kernel - Re: [PATCH 1/4] compiler.h: introduce unused

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]

Message-ID: <4F9A55EC.20804@zytor.com>
Date:	Fri, 27 Apr 2012 01:16:44 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 1/4] compiler.h: introduce unused_expression() macro

On 04/25/2012 04:26 AM, Konstantin Khlebnikov wrote:
> Sometimes we want to check some expressions correctness in compile-time without
> generating extra code. "(void)(e)" does not work if expression has side-effects.
> This patch introduces macro unused_expression() which helps in this situation.
> 
> Cast to "long" required because sizeof does not work for bit-fields.
> 
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...nvz.org>
> ---
>  include/linux/compiler.h |    2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/include/linux/compiler.h b/include/linux/compiler.h
> index 923d093..46fbda3 100644
> --- a/include/linux/compiler.h
> +++ b/include/linux/compiler.h
> @@ -310,4 +310,6 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
>   */
>  #define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
>  
> +#define unused_expression(e) ((void)(sizeof((__force long)(e))))
> +

OK, bikeshedding a bit:

"unused_expression()" doesn't sound like something that inhibits side
effects, especially since "unused" applied to an argument or variable
means "don't make a fuss over this not being used."

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

--
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/