Recently, qemu iotest 013 has started to fail for me: Fedora release 22 (Twenty Two)
3.5.0-9.fc22 clang version 3.5.0 (tags/RELEASE_350/final) Target: x86_64-redhat-linux-gnu Thread model: posix +4 KiB/home/jsnow/src/qemu/qemu-io-cmds.c:230:18: runtime error: division by zero 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. Two workarounds: (1) Modify the tdiv() function to just return INFINITY manually if the timestamp provided is 0 (2) Modify tester scripts to also use -fno-sanitize=float-divide-by-zero I prepared a patch to do the first workaround [1] so I could test patches with clang in peace as I need to test my pull requests under clang to make sure I don't break OSX, but it seems so absurd to have to do this, so I have copied our resident language lawyers (and language pragmatists) so that they can have a say. Relevant upstream BZ: https://llvm.org/bugs/show_bug.cgi?id=17000 --js [1] https://github.com/jnsnow/qemu/commit/af93977dd2bc7ea936b8064c41c5a0f9d25ae2d1
