Date: Thu, 11 Dec 2008 11:06:16 +0100
From: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
To: Alex Raimondi <mailinglist@miromico.ch>
Cc: kernel@avr32linux.org, linux-kernel@vger.kernel.org
Subject: Re: Segfault in fbcmap.c => Compiler bug?
Message-ID: <20081211110616.72f2d937@hskinnemoen-d830>
In-Reply-To: <4940CE1F.5080605@miromico.ch>
References: <4940CE1F.5080605@miromico.ch>
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Alex Raimondi wrote:
> 			if (transp) 
> 				htransp = *transp++;
> 
> 
> The segfault happens at the if (transp) statment.
> 
> Now to the strange thing, which makes me guess this may be a problem related to a compiler bug:
> 
> When I change the if statment to:
> 
> 			if (transp) {
> 				printk("e\n");
> 				htransp = *transp++;
> 			}

Yeah, as HC pointed out, this is caused by a buggy toolchain. Although
I don't have any disassembly to back it up, I'm willing to bet that it
will show an unconditional load followed by a conditional mov. The
printk() implies a barrier, which will prevent the faulty optimization
from happening.

Haavard
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