Re: [PATCH jiffies] Avoid undefined behavior from signed overflow

From: Kevin Easton
Date: Mon Jul 29 2013 - 10:08:51 EST

Quoting "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>:

On Mon, Jul 29, 2013 at 03:30:35PM +1000, caf@xxxxxxxxxxx wrote:
Quoting "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>:

>Note that the C standard considers the cast from signed to
>unsigned to be implementation-defined, see

Don't worry, the case from signed to unsigned is actually well-defined -
the relevant part is (in C99):

>Otherwise, if the new type is unsigned, the value is converted by
>repeatedly adding or subtracting one more than the maximum value that
>can be represented in the new type until the value is in the range of
>the new type.

Yep, but we are going in the other direction, from unsigned to signed.

Ahh, there's an error in the commit message (it says signed to unsigned).

- Kevin

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