From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Kevin Easton <kevin@guarana.org>
Cc: linux-kernel@vger.kernel.org, john.stultz@linaro.org,
davem@davemloft.net, arnd@arndb.de, mingo@kernel.org,
torvalds@linux-foundation.org
Subject: Re: [PATCH jiffies] Avoid undefined behavior from signed overflow
Date: Mon, 29 Jul 2013 07:28:12 -0700 [thread overview]
Message-ID: <20130729142812.GN26694@linux.vnet.ibm.com> (raw)
In-Reply-To: <20130730000103.35524r83mpydvs7z@chicago.guarana.org>
On Tue, Jul 30, 2013 at 12:01:03AM +1000, Kevin Easton wrote:
> Quoting "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>:
>
> >On Mon, Jul 29, 2013 at 03:30:35PM +1000, caf@guarana.org wrote:
> >>Quoting "Paul E. McKenney" <paulmck@linux.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
next prev parent reply other threads:[~2013-07-29 14:28 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-27 22:58 [PATCH jiffies] Avoid undefined behavior from signed overflow Paul E. McKenney
2013-07-28 18:46 ` Eric Dumazet
2013-07-29 2:55 ` Paul E. McKenney
2013-07-29 5:30 ` caf
2013-07-29 13:54 ` Paul E. McKenney
2013-07-29 14:01 ` Kevin Easton
2013-07-29 14:28 ` Paul E. McKenney [this message]
2013-08-04 19:16 ` Linus Torvalds
2013-08-04 20:20 ` Paul E. McKenney
2013-08-04 20:23 ` Linus Torvalds
2013-08-04 20:34 ` Paul E. McKenney
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