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Thread: QT dialogs loaded as DLLs in QT5 seem to be not safe against unload procedures

  1. #1
    Join Date
    Apr 2010
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    MacOS X

    Default QT dialogs loaded as DLLs in QT5 seem to be not safe against unload procedures

    Hi everyone,
    I have a QT application which is started as an executable. In that application, I load components stored in DLLs, each coming along with a dialog window.
    System is Windows 7, VS2012 and Qt 5.1.1 compiled from sources by the way.

    This worked well for a long time in QT4 but now that I switched to QT5, there are numerous problems. Those problems are related to the fact that DLLs are properly loaded with all symbols and stuff but the unload does not really work properly in QT5.
    I first reported a problem here

    and finally solved this issue myself by fixing the respective lines of code. However, when reporting this as a bug, the answer was that unloading DLLs with metatypes is not supported,

    Once I had fixed that problem, I started to run into the next problem which was related to a QFontCache behavior which seemed not to be safe against unload of DLLs. I did not check the reason for this in detail since I need to use QT and do not have too much time to take part in the development.

    So, here is my question: is it worth checking the reason for these types of errors or is the concept of "unloading QT DLLs" a feature which is not meant to be supported? My feeling would be that unloading DLLs should be supported whenever loading DLLs is. So, could anyone comment on this?
    If it is not supported officially I will either return back to QT4 which did not make any problem in this regard or I will remove the "dynamic load of components" feature.

    Thank you for any comment and best regards


  2. #2
    Join Date
    Jan 2006
    Graz, Austria
    Thanked 1,546 Times in 1,496 Posts
    Qt products
    Qt3 Qt4 Qt5
    Unix/X11 Windows

    Default Re: QT dialogs loaded as DLLs in QT5 seem to be not safe against unload procedures

    I guess a question like that is better directed at the people developing Qt.

    E.g. on the Qt development list


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