linux-kernel - Re: [PATCH 5/5 ver2] debug: BUILD_BUG_ON: error on non-const expressions

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Message-Id: <200810021535.36302.rusty@rustcorp.com.au>
Date:	Thu, 2 Oct 2008 15:35:35 +1000
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Boaz Harrosh <bharrosh@...asas.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	"David S. Miller" <davem@...emloft.net>,
	Ivo van Doorn <IvDoorn@...il.com>,
	"John W. Linville" <linville@...driver.com>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Theodore Tso <tytso@....edu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jan Beulich <jbeulich@...ell.com>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/5 ver2] debug: BUILD_BUG_ON: error on non-const expressions

On Wednesday 03 September 2008 01:57:31 Boaz Harrosh wrote:
> +#define BUILD_BUG_ON(e) \
> +       do { struct {int:-!!(e); } x __maybe_unused;} while(0)

Why did you hate the void cast again?  Simplest should 
be "(void)BUILD_BUG_ON_ZERO(e)".  But if not, it seems to me that it's 
cleaner to do:

#define BUILD_BUG_ON(e) \
	do { } while(BUILD_BUG_ON_ZERO(e))

No chance of the compiler emitting unused vars.

Cheers,
Rusty.

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