Date: Sat, 17 Nov 2012 15:38:41 +0100
From: Borislav Petkov <bp@alien8.de>
To: Daniel Santos <daniel.santos@pobox.com>
Cc: LKML <linux-kernel@vger.kernel.org>, Andi Kleen <ak@linux.intel.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Christopher Li <sparse@chrisli.org>,
        David Daney <david.daney@cavium.com>,
        David Howells <dhowells@redhat.com>, Joe Perches <joe@perches.com>,
        Josh Triplett <josh@joshtriplett.org>,
        Konstantin Khlebnikov <khlebnikov@openvz.org>,
        linux-sparse@vger.kernel.org, Michel Lespinasse <walken@google.com>,
        Paul Gortmaker <paul.gortmaker@windriver.com>,
        Pavel Pisa <pisa@cmp.felk.cvut.cz>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH v5 6/9] bug.h: Prevent double evaulation of in
 BUILD_BUG_ON
Message-ID: <20121117143840.GB16441@x1.osrc.amd.com>
Mail-Followup-To: Borislav Petkov <bp@alien8.de>,
	Daniel Santos <daniel.santos@pobox.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Andi Kleen <ak@linux.intel.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Christopher Li <sparse@chrisli.org>,
	David Daney <david.daney@cavium.com>,
	David Howells <dhowells@redhat.com>, Joe Perches <joe@perches.com>,
	Josh Triplett <josh@joshtriplett.org>,
	Konstantin Khlebnikov <khlebnikov@openvz.org>,
	linux-sparse@vger.kernel.org, Michel Lespinasse <walken@google.com>,
	Paul Gortmaker <paul.gortmaker@windriver.com>,
	Pavel Pisa <pisa@cmp.felk.cvut.cz>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Steven Rostedt <rostedt@goodmis.org>
References: <1352844568-18826-1-git-send-email-daniel.santos@pobox.com>
 <1352844821-18952-6-git-send-email-daniel.santos@pobox.com>
 <20121115150726.GD4956@x1.osrc.amd.com>
 <50A53E53.8080404@att.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <50A53E53.8080404@att.net>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 973
Lines: 24

On Thu, Nov 15, 2012 at 01:11:15PM -0600, Daniel Santos wrote:
> Ah yes. I did notice that at one point, but I think it slipped
> my mind. Also, the kernel has introduced me to the usage of the
> !! construct, of which I'm well versed in its affects in various
> situations and how gcc's optimizer ends up treating its usage, so
> probably another reason I didn't change it immediately. But it's
> basically shorthand for the expression (condition ? 1 : 0), correct?

I don't think so: "!!" is simply a double negation which turns the
whatever wild construct you have into either 0 or 1, depending on what
it evaluates to.

But I don't know what the standard says so you'll have to check :-)

Thanks.

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