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Date: Wed, 16 Jun 2010 07:34:51 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] [PATCH] Fix comparison which always returned false
References: <1276635808-7315-1-git-send-email-weil@mail.berlios.de>
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To: Richard Henderson <rth@twiddle.net>
Cc: Anthony Liguori <aliguori@us.ibm.com>, QEMU Developers <qemu-devel@nongnu.org>, Gleb Natapov <gleb@redhat.com>

On 06/15/2010 07:27 PM, Richard Henderson wrote:
> On 06/15/2010 02:28 PM, Anthony Liguori wrote:
>    
>> On 06/15/2010 04:03 PM, Stefan Weil wrote:
>>      
>>> Comparing an 8 bit value with ~0 does not work as expected.
>>> Replace ~0 by UINT8_MAX in comparison and also in assignment
>>> (and fix coding style, too).
>>>
>>>        
>> Because when the uint8_t gets promoted, it doesn't get zero filled.  I'd
>> rather something a bit more obvious like HPET_INVALID_COUNT.
>>      
> Er, yes it does.  The problem is that it *did* get zero-extended,
> but ~0 is 0xffffffff, so the comparison fails.
>    

Typo on my part.  I meant one filled obviously.

Regards,

Anthony Liguori

> But I really agree with Jan Kiszka down-thread -- why do we need
> to signal this as a special case at all?
>
>
> r~
>