From mboxrd@z Thu Jan  1 00:00:00 1970
From: Josh Triplett <josh@joshtriplett.org>
Subject: Re: [PATCH v2 07/10] compiler.h, bug.h: Prevent double error
 messages with BUILD_BUG{,_ON}
Date: Fri, 5 Oct 2012 13:59:22 -0700
Message-ID: <20121005205922.GA7362@jtriplet-mobl1>
References: <1349465759-20524-1-git-send-email-daniel.santos@pobox.com>
 <1349466169-20637-7-git-send-email-daniel.santos@pobox.com>
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To: danielfsantos@att.net
Cc: LKML <linux-kernel@vger.kernel.org>, Andi Kleen <ak@linux.intel.com>, Andrea Arcangeli <aarcange@redhat.com>, Andrew Morton <akpm@linux-foundation.org>, Borislav Petkov <bp@alien8.de>, Christopher Li <sparse@chrisli.org>, David Daney <david.daney@cavium.com>, David Howells <dhowells@redhat.com>, David Rientjes <rientjes@google.com>, Joe Perches <joe@perches.com>, 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>, Daniel Santos <daniel.santos@pobox.com>

On Fri, Oct 05, 2012 at 02:42:46PM -0500, danielfsantos@att.net wrote:
> --- a/include/linux/compiler.h
> +++ b/include/linux/compiler.h
> @@ -296,6 +296,11 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
>  #endif
>  #ifndef __compiletime_error
>  # define __compiletime_error(message)
> +# define __compiletime_error_fallback(condition) \
> +	 ((void)sizeof(char[1 - 2*!!(condition)]))
> +#endif
> +#ifndef __compiletime_error_fallback
> +# define __compiletime_error_fallback(condition) (void)(0)

Might want to use do { } while (0) here, to force the use of a
semicolon and avoid the use of __compiletime_error_fallback in an
expression.

- Josh Triplett