UBSAN misaligned address errors

[jeroen]

See http://www.stats.ox.ac.uk/pub/bdr/memtests/gcc-UBSAN/brotli-Ex.Rout

[eustas]

Try to compile with -DBROTLI_BUILD_PORTABLE option

[jeroen]

Thanks. Not sure if that justifies undefined behavior in the default build though.

[eustas]

We focused mostly on x64 and ARMv7 where unaligned read doesn't cause undefined behaviour (except for atomicity, but it's not the case).
We will consider to turn this optimisation only when compiler detects compatible CPU architecture.

[jeroen]

I think you are mistaken, these UBSAN errors appear on linux on x86_64.

[eustas]

Yes, ubsan reports errors on x86_64 and we used it to check "portable" version.
But reporting unaligned reads by ubsan on x86_64 is done intentionally, so developers could verify their product without compiling for / running on specific hardware that can't to unaligned reads.