Threads still running after QFuture waitForFinished

ktwolff

A simple Windows 7 QT5.7 console project with no QCoreApplication has the following code in it:

QFuture<void > f = QtConcurrent::mapped(list ,function);
f.waitForFinished();
exit(0);

This results in an error message per core on the console:

QWaitCondition: Destroyed while threads are still waiting
QWaitCondition: Destroyed while threads are still waiting
QWaitCondition: Destroyed while threads are still waiting
QWaitCondition: Destroyed while threads are still waiting

Shouldn't f.waitForFinished() ensure that the threads created have terminated? They seem to hang around for a long time, until the program runs a new QtConcurrent::mapped

kshegunov

@ktwolff
Hello,

exit(0);

why???!!!

Shouldn't f.waitForFinished() ensure that the threads created have terminated?

No, it ensures your job has finished. The QtConcurrent module manages a thread pool that will be initialized or deinitialized when the module deems fit (on startup/shutdown).

Kind regards.

ktwolff

@kshegunov Many thanks!

I placed an exit in my code debugging something and I was curious...

Ken

kshegunov

@ktwolff

I placed an exit in my code debugging something and I was curious...

Well that's the reason for getting the warnings, as exit is really notorious way to quit the application. Long story - short, one shouldn't use it, save for exceptional circumstances.

Kind regards.