On 02/02/2016 01:03 PM, John Snow wrote: > The problem is that in the print report for read_f, t2 and t1 can > actually be the same exact timestamp, and tdiv will try to divide by 0.0. > > Normally this is not a problem as this is defined to be INFINITY in C99 > Annex F. > > Clang, however, has once again decided to take the pedantic road and > state that Annex F is optional, and therefore division by 0.0 is > actually undefined when using -fsanitize=undefined. > > Groan.
No kidding. :( A compiler ceases to be useful when it spews out noise "just because it can". > > Two workarounds: > > (1) Modify the tdiv() function to just return INFINITY manually if the > timestamp provided is 0 Seems reasonable to me. > https://github.com/jnsnow/qemu/commit/af93977dd2bc7ea936b8064c41c5a0f9d25ae2d1 I'd be okay with this patch, if you want to make it a formal submission, and if no one else chimes in with any opinion other than disgust at clang's shenanigans. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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