Re: [Xen-devel] [PATCH 09/14] xen: events: Remove redundant check on unsigned variable

[Tushar Behera <tushar.behera@xxxxxxxxxx>]

On 11/19/2012 04:01 PM, Ian Campbell wrote:
> On Mon, 2012-11-19 at 03:52 +0000, Tushar Behera wrote:
>> On 11/16/2012 10:23 PM, Jeremy Fitzhardinge wrote:
>>> To be honest I'd nack this kind of patch. The test is only redundant in the 
>>> most trivial sense that the compiler can easily optimise away. The point of 
>>> the test is to make sure that the range is OK even if the type subsequently 
>>> becomes signed (to hold a -ve error, for example).
>>>
>>> J
>>>
>>
>> The check is on the function argument which is unsigned, so checking '<
>> 0' doesn't make sense. We should force signed check only if the argument
>> is of signed type. In any case, even if irq has been assigned some error
>> value, that would be caught by the check irq >= nr_irqs.
> 
> Jeremy is (I think) arguing that this check is not redundant because
> someone might change the type of the argument to be signed and until
> then the compiler can trivially optimise the check away, so what's the
> harm in it?
> 
> I'm somewhat inclined to agree with him.
> 
> Ian.
> 
Ok, I don't have much argument against this.

-- 
Tushar Behera

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