Mon Jun 8 05:25:55 UTC 2015

...

UBSAN seems expensive and doesn't seem it would run other than test, but I didn't work on it long and am not 100% certain. Was trying ASAN extra stack checking at the time, which may have been the culprit.

As I said in my previous email, if you're running releases before 0.2.6.6 (2015), Tor won't run under UBSAN due to issues that have been fixed in subsequent releases.

Had a need to run ASAN+UBSAN and it works perfectly fine for me with version 0.2.4.27. Required a minor patch to convert a single common variable 'incoming_queue' to extern. Performance hit was not as bad as I thought from the earlier try, but bad enough that I limited the instrumented modules to only what's necessary.