AddressSanitizer and ThreadSanitizer (https://github.com/google/sanitizers) are projects initially developed by Google Inc. Both tools consist of a compiler module and a run-time library. The sources of the run-time library for these projects are hosted at https://llvm.org/svn/llvm-project/compiler-rt in the following directories: include/sanitizer lib/sanitizer_common lib/interception lib/asan lib/tsan lib/lsan lib/ubsan Trivial and urgent fixes (portability, build fixes, etc.) may go directly to the GCC tree. All non-trivial changes, functionality improvements, etc. should go through the upstream tree first and then be merged back to the GCC tree. The merges from upstream should be done with the aid of the merge.sh script; it will also update the file MERGE to contain the upstream revision we merged with.