linux-kernel - Re: [PATCH] Make WARN_ON/WARN_ON_ONCE no-ops when CONFIG

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Date:	Fri, 14 Dec 2007 12:02:46 -0600
From:	Matt Mackall <mpm@...enic.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Make WARN_ON/WARN_ON_ONCE no-ops when CONFIG_BUG is off

On Fri, Dec 14, 2007 at 09:27:55PM +0800, Herbert Xu wrote:
> Hi:
> 
> [PATCH] Make WARN_ON/WARN_ON_ONCE no-ops when CONFIG_BUG is off
> 
> The description of CONFIG_BUG clearly states that both BUG and
> WARN_ON may be skipped.  However, our actual implementation still
> checks the condition on WARN_ON if it's used as part of an if
> statement or such.
> 
> This patch makes it return 0 after evaluating the expression
> if CONFIG_BUG is disabled.  This is consistent with the spirit
> of the CONFIG_BUG option.

I added CONFIG_BUG, and I think the current behavior is correct. As
you've noticed, we have to evaluate condition, it may have
side-effects. And if code does:

	/* this indicates a driver bug, report and fail gracefully */
	if (WARN_ON(val == NULL))
		return -EFAULT;

..we surely want it to continue returning -EFAULT, regardless of
whether we log it, no? What use case did you have in mind?

-- 
Mathematics is the supreme nostalgia of our time.
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