This commit adds one unusual creation and three more unusual exits: * creation of the Q*Application in a thread (QTBUG-130895) * exits using ::exit() instead of returning from main(): * from the main thread's event loop * from an auxiliary thread * from inside an auxiliary thread's event loop All of these exercise the moment the QAdoptedThread & QThreadData for the main thread is destroyed, which are, respectively: * thread exit time, running thread-specific destructors * inside exit(), running atexit()-like callbacks (qthread_*.cpp) * [tst_static_q*application] inside exit(), running static destructors (added in commit 1da7558bfd7626bcc40a214a90ae5027f32f6c7f) Unlike the tst_static_q*application tests, the calls to ::exit() cannot be a regular QtTest because that would cause the log output to be incomplete. The threaded Q*Application could be a test of its own, but since I needed to add the helper anyway, I chose to add the test there. For the majority of the tests, the failure mode is going to be a crash on exit. Task-number: QTBUG-12673 Task-number: QTBUG-132429 Pick-to: 6.8 6.9 Change-Id: I1062ef500356bd97dd0cfffda4aeeda9afa138e8 Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>