[PATCH 2/2] os: Work around integer overflow in TimerSet.

[walter harms]

Am 06.03.2011 21:34, schrieb Fernando Carrijo:
> Cyril Brulebois <kibi at debian.org> wrote:
> 
>> If TimerSet gets called with a big timeout, this call can overflow:
>>   millis += now;
>>
>> Detect overflow and set millis to the maximal integer when that happens,
>> to avoid falling in the “already expired” case.
> 
> Hi Cyril,
> 
> I found this, buried in Section 6.2.5 (9) of the C Standard:
> 
>     A computation involving unsigned operands can never overflow,
>     because a result that cannot be represented by the resulting
>     unsigned integer type is reduced modulo the number that is one
>     greater than the largest value that can be represented by the
>     resulting type.
> 

What they mean is: we will not access a memoryadress beyond because any
overflow will return to zero.
for uchar this means:  0xff +0x1 -> 0x00  what is still a char.

re,
 wh


> So, I presume, something isn't quite right in this series.
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