Messages in this thread | | | Date | Wed, 26 Nov 2014 10:23:45 -0800 | Subject | Re: [RFC 2/2] kvm: eventfd: detect integer overflow using check_*_overflow | From | Linus Torvalds <> |
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On Wed, Nov 26, 2014 at 9:55 AM, Sasha Levin <sasha.levin@oracle.com> wrote: > > Good point. Do you think there's an advantage in using GCC's overflow > checker in this case?
No. However, if your coccinelle script can be changed to verify that the type of the expression is unsigned, _that_ would be useful.
And the "multiplication overflow" may actually be a way to generate better code. Possibly. I'm not entirely sure exactly what gcc actually does. How many multiplication overflow tests do we actually have, though?
For plain unsigned additions, "a + b < a" is already optimal (ie gcc realizes it's an overflow check and generates a test against the carry flag, at least when it doesn't screw up)
Linus
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