I recently found this error on a debian (bookworm) system, but it can easily be reproduced on ubuntu-latest as well (I reproduced it on github CI: https://github.com/popovec/mosquitto/actions/runs/7168761732/job/19517643695).

The error is related to the library - the comment in the test explains more:

/* mosquitto_connect_async() test, with mosquitto_loop_start() called after mosquitto_connect_async(). */

Since the PR acceptance conditions state that the author will check the code using make test, it would be nice if make test worked without problems on the current master.

I can prepare a PR that will introduce this automatic test on github CI: master...popovec:mosquitto:linux-build-test