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Date: Mon, 29 Jul 2013 07:28:12 -0700 From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> To: Kevin Easton <kevin@...rana.org> Cc: linux-kernel@...r.kernel.org, john.stultz@...aro.org, davem@...emloft.net, arnd@...db.de, mingo@...nel.org, torvalds@...ux-foundation.org Subject: Re: [PATCH jiffies] Avoid undefined behavior from signed overflow On Tue, Jul 30, 2013 at 12:01:03AM +1000, Kevin Easton wrote: > Quoting "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>: > > >On Mon, Jul 29, 2013 at 03:30:35PM +1000, caf@...rana.org wrote: > >>Quoting "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>: > >> > ... > >>> > >>>Note that the C standard considers the cast from signed to > >>>unsigned to be implementation-defined, see 6.3.1.3p3. > ... > >> > >>Don't worry, the case from signed to unsigned is actually well-defined - > >>the relevant part is 6.3.1.3p2 (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). Good catch, fixed! Thanx, Paul -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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