How to correctly unload QApplication in a DLL?

[maisoui]

I do this dummy code just to reproduce the issue. I know that myObject variable and variant are unused, but Qt crash the second time I reload the module.

Once again, I guess the issue is coming from new structure (Qt5) of QMetaType and QVariant. I need to be able to unregister custom types or completely unload Qt libraries.

[maisoui]

Yes, qApp can be NULL (from documentation: Returns a pointer to the application's QCoreApplication (or QApplication) instance. If no instance has been allocated, null is returned). But don't focus on that, If I change the code like this, problem is the same.
@int argc = 0;
myApplication = new QApplication(argc, NULL);

...

delete myApplication;@

[AlterX]

I don't think this is your problem...you are just setting a normal variable (QVariant) with another variable (MyObject)...problem is on qApp stuff.
Can you check if second time a new QApplication is created again?

[maisoui]

Checked. The second time a new QApplication is created too.

[sierdzio]

I think you would get better answers on the interest mailing list. People fluent in QtCore code are likely to know the cause of your problem.

[AlterX]

Anyway scenario is very complex since you are using a static object in process with another application (autocad) and managing a QApplication using qApp that can have different scope and logic behind.
Can you tell me why are you using QApplication and if you remove those instructions if it is working

[maisoui]

As with any Qt application, I need to create a valid QApplication. I'm surprised by your question.

[AlterX]

I don't understand...you are creating a plugin for Autocad if you don't need gui why are you using Qt?
and again I don't think this is the correct approch to check qApp and create an anonymous QApplication without an explicit reference

[sierdzio]

AlterX QObject class requires a valid QCoreApplication instance to work properly.

[maisoui]

Yes, and I need GUI. I do a little condensed code just to reproduce the issue. Of course, this is not my whole application. It's just a "debug" example.

[AlterX]

Ok, so due to this problem can be related to in process plugin, it is very hard to help you since we don't know how to reproduce this on our own. Maybe you can try to not unload the entire plugin and reload it, and have a only one instance of QApplication created when you load plugin? Can you do this?

[AlterX]

[quote author="sierdzio" date="1417515370"]AlterX QObject class requires a valid QCoreApplication instance to work properly.[/quote]

Yes I know of course, but since he spoke about just an example I was thinking that original code was not using Qt and that this was just a curious question for him