I was putting together some additional testing for a library and my CI jobs were failing in release mode. I was able to reproduce the issue locally. On examination of the boost test matrix however I was unable to see the same failures. When I dug into it a little bit more, it looks like the clang linux build jobs only build the default variant (debug), and therefore will not catch release-mode optimization issues when running the unit tests. Here's one of the job details: https://www.boost.org/development/tests/develop/teeks99-02-dc6-17-Docker-64o... Given this matrix is the last line of defense before code is merged from develop to master, I'd suggest that the build jobs should all be targeting variant=release instead of variant=debug. The former directly impacts a release, and the latter does not. - Jim