Hi, At Mozilla, we've encountered a GCC 4.6 miscompilation in the ARMv6 build of Firefox for Android. We'd like to evaluate whether this bug is hitting us in more places than the one we spotted. To that end, we'd need to know what particular bug in GCC leads to this miscompilation.
The attached file is the preprocessed source, slightly simplified. I was able to reproduce the miscompilation with both the GCC 4.6 from the Android NDK r8d and 4.6.3 from Debian unstable. It apparently happens for any -march, with -marm, but not -mthumb. It happens at -Os but not -O2. The problematic assembly looks like the following. It corresponds to the C code after the second call to DER_SetUInteger in sftk_mkPrivKey:: bl DER_SetUInteger(PLT) mov r3, #0 cmp sl, r3 movne r0, #2 moveq r0, r3 sl/r10 is never set anywhere in the function, so we're getting random behaviour. This doesn't happen with GCC 4.7, which suggests it may be a known bug. Any ideas? Cheers, Mike
