On 09/08/2015 01:40 PM, Mathieu Malaterre wrote: > On Tue, Sep 8, 2015 at 2:00 PM, Mathieu Malaterre <malat@xxxxxxxxxx> wrote: >> FYI, >> >> On Tue, Sep 8, 2015 at 12:04 PM, Jonathan Wakely <jwakely.gcc@xxxxxxxxx> wrote: >> [...] >>> That's not the only option. You could compile one file with GCC and >>> all others with Clang and see if you can reproduce it. Repeat for each >>> file, which will narrow down the file where the problem occurs. Then >>> you can try splitting that file into smaller pieces, with one function >>> per file, and repeat the process. That would tell you which function >>> or functions get miscompiled by GCC. >> >> Ok so if I compile eveything with gcc and then only `tcd.c` using >> clang, then everything works as expected (no symptoms). >> ref: https://github.com/uclouvain/openjpeg/blob/master/src/lib/openjp2/tcd.c >> >> I'll repeat your approach to find the culprit function. > > And the culprit function is `opj_tcd_makelayer`: > > https://github.com/uclouvain/openjpeg/blob/master/src/lib/openjp2/tcd.c#L218 > > Other than the `if (dd / dr >= thresh)` I do not see anything > obviously suspicious. I see floating point, despite your earlier denial. :-) Libopenjpeg has a bad reputation for messing with the floating- point state. Please make sure the library is not linked with -ffast-math. Beyond that, a few printf()s and "diff" should find the problem. Andrew.
