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Date: Wed, 20 Aug 2008 12:59:22 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Boaz Harrosh <bharrosh@panasas.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Alexey Dobriyan <adobriyan@gmail.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Sam Ravnborg <sam@ravnborg.org>
Subject: Re: [PATCH] debug: fix BUILD_BUG_ON() for non-constant expressions
Message-ID: <20080820105922.GC18524@elte.hu>
References: <20080816100948.GB19926@martell.zuzino.mipt.ru> <alpine.LFD.1.10.0808170936260.3324@nehalem.linux-foundation.org> <20080817173319.GA2450@elte.hu> <200808181109.43203.rusty@rustcorp.com.au> <20080818075459.GH30694@elte.hu> <48A9472F.908@panasas.com> <20080819133422.GA24369@elte.hu> <48AAF5F7.6040709@panasas.com>
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* Boaz Harrosh <bharrosh@panasas.com> wrote:

> If the user of virtio_has_feature() must pass a compile-time constant 
> then it must be converted to a MACRO, and then the BUILD_BUG_ON will 
> work. Or it should be changed to a BUG_ON() if fbit is a runtime 
> variable.

well, that's the question i'm asking: that sort of proposed 
BUILD_BUG_ON() variantcannot be used in inline functions like 
virtio_has_feature() does. If we get forced back to macros that's not an 
improvement.

Maybe the link-time last-line-of-defense mechanism i posed is the most 
flexible one perhaps after all? (it's ugly too but none of this is 
particularly pretty)

hm?

	Ingo