"Resource th is acquired by class cleaner but not released anywhere in this class."

The resource is acquired when main invokes start on the cleaner class. It is released when main invokes stop on it. It always do so (check src/main.cpp for main()). Note that the helper function join_thread is used for it which can be found in src/exec.cpp

https://lgtm.com/projects/g/flok99/constatus/snapshot/588bdaead6294fc99fc160d9f5ccfd829304696e/files/src/cleaner.cpp?sort=name&dir=ASC&mode=heatmap#L34