linux-kernel - Re: [PATCH 11/11] Use unreachable() in asm-generic/bug.h for !CONFIG

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Date:	Mon, 14 Sep 2009 16:39:46 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	David Daney <ddaney@...iumnetworks.com>
cc:	Brian Gerst <brgerst@...il.com>, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH 11/11] Use unreachable() in asm-generic/bug.h for 
 !CONFIG_BUG case.

On Mon, 14 Sep 2009, David Daney wrote:
> 
> The existing code just falls through to whatever happens to follow the BUG().

Brian was talking BUG_ON().

And the existing !CONFIG_BUG BUG_ON() is actually set up so that gcc will 
just optimize it away entirely (yet give the same compile-time warnings as 
the "real" BUG_ON() does).

Changing it to "if (cond) unreachable()" is likely to generate _more_ 
code, which is against the whole point of wanting to disable CONFIG_BUG.

			Linus
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