Summary:
Undefined Behavior Sanitizer (ubsan) is //a good thing// which will help us to find sneaky bugs with low cost. Please see http://developerblog.redhat.com/2014/10/16/gcc-undefined-behavior-sanitizer-ubsan/ for more details and official GCC documentation for more context: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html.
Changes itself are quite simple and pretty much imitating whatever is implemented for ASan.
Hooking the UBsan validation build to Sandcastle is a separate step and will be dealt as separate diff because code is in internal repository.
Test Plan: Make sure that that there no regressions when it comes to builds and test pass rate.
Reviewers: leveldb, sdong, IslamAbdelRahman, yhchiang
Reviewed By: yhchiang
Subscribers: andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D56049
994b3bd693