Priority: P3: Somewhat important
Affects Version/s: 5.15.0
Fix Version/s: None
QHostInfoLookupManager connects a signal handler to `QCoreApplication::destroyed` that waits until all threads from`QHostInfoLookupManager::threadPool` are done (see QHostInfoLookupManager::QHostInfoLookupManager()).
However, depending on the system integration, those threads may hang for up to 10 - 15sec. Thus, quitting an app would be delayed by the same amount of time.
For example, quitting the sample app provided in attachments always hang with the following setup:
- Linux 5.4.
- Qt v5.15.0.
- Connman v1.37.
- Connman runs without --nodnsproxy, so it proxies dns resolution.
- System has no network access (system cannot reach external dns server).
Qt shouldn't rely on system level timeouts to quit an app. I would have expected Qt to force quit the threads if they are not done after a small timeout window defined by Qt.