[Qt-interest] QtGui4.dll and QtCore4.dll don't unload, when using QFileSystemModel!

[Niels Dekker - no return address]

We're developing a DLL, "OurWidget.dll", containing a widget derived 
from a Qt4 QMainWindow. The user of the DLL does not need to use Qt 
directly. MFC applications and console applications can just link to 
"OurWidget.dll", which will indirectly load the necessary Qt DLL's: 
QtGui4.DLL, QtCore4.dll, and QtXml4.dll.  Our widget has a tree view, 
ourTreeView, which may have a model of type QFileSystemModel.

Now when our widget has indeed used a QFileSystemModel while it is 
loaded, "QtGui4.DLL" and "QtCore4.dll" will not unload anymore, 
afterwards!  Not even when the "OurWidget.dll" is unloaded! 
("QtXml4.dll" is unloaded properly, though.)  Moreover, the application 
may become unstable afterwards!

Is this a known issue of QFileSystemModel?  Is there a workaround?

We're using Qt 4.5.2, and our "OurWidget.dll" links at compile-time 
("early binding") to QtGui4.lib, QtCore4.lib, and QtXml4.lib.  We 
monitored loading and unloading of DLL's by Dependency Walker 
(www.dependencywalker.com).

Hope you can help,

  Niels

--
Niels Dekker
http://www.xs4all.nl/~nd/dekkerware
Scientific programmer at LKEB, Leiden University Medical Center