[Development] QT dialogs loaded as DLLs in QT5 seem to be not safe against unload procedures

[Thiago Macieira]

Em seg 24 fev 2014, às 21:01:41, Hauke Krüger escreveu:
> 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 in QT5? My feeling would be that unloading
> DLLs should be supported whenever loading DLLs is. So, could anyone
> comment on this?

Fair enough. Then manual dynamic loading of the Qt libraries is not supported. 
We don't test it, so it may or may not work for you. Since we can't tell you 
it works, we have to call it "not supported".

That said, we may be able to accept patches, depending on what the fix is. It's 
hard to say what the QFontCache problem might be and whether the solution 
might be accepted or not, without some investigation or at least some detail 
of what's happening.

My recommendation is that, if you unload any library or plugin that registers 
metatypes, you must cause QtCore to unload too. The same applies to other Qt 
libraries: if one gets unloaded, then all of them must get unloaded too.

> 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.

It wasn't supported either. It just happened to work.

> Thank you for any comment and best regards

-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel Open Source Technology Center