linux-kernel - Re: [PATCH] fix BUILD_BUG_ON() and a couple of bogus uses of it

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Message-Id: <20090917.174530.262030717.davem@davemloft.net>
Date:	Thu, 17 Sep 2009 17:45:30 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	akpm@...ux-foundation.org
Cc:	JBeulich@...ell.com, linux-kernel@...r.kernel.org,
	sparclinux@...r.kernel.org
Subject: Re: [PATCH] fix BUILD_BUG_ON() and a couple of bogus uses of it

From: David Miller <davem@...emloft.net>
Date: Thu, 17 Sep 2009 17:31:54 -0700 (PDT)

> From: Andrew Morton <akpm@...ux-foundation.org>
> Date: Thu, 17 Sep 2009 17:15:04 -0700
> 
>> There's a shortcoming in the current BUILD_BUG_ON() - it silently does
>> nothing if passed a non-constant arg.
>> 
>> I suspect that in the 2.6.31 code, that BUILD_BUG_ON() just does
>> nothing at all, and that Jan's patch is now exposing this.  It might be
>> compiler-version dependent too.
>> 
>> 
>> <tests it>
>> 
>> Yup, on base 2.6.31, this:
> 
> Ok, I'll have to either change this function to a macro or
> get rid of the check.

I can't even get GCC to see the constant evaluated by is_power_of_2().

I give up, I'll just remove the BUILD_BUG_ON() entirely.
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