[Interest] Two QCoreApplication objects with a twist

[Lorenz Haas]

Hi,

you can't use two QCoreApplication instances in a single application,
I know. There's also a nice warning:
https://github.com/qt/qtbase/blob/5.10/src/corelib/kernel/qcoreapplication.cpp#L795.
The reason, I guess, has to do with the static variables used in QCA
(?).

Now, however, please imagine the following scenario and please be
assured that I am neither convinced by nor advising such an
architecture:

- Win32 based
- Main Application uses Qt5 with QApplication
- Shared library linked against Qt4 (Core)
- Qt5-Application uses the library
- This Qt4-linked library starts an Qt4-QCoreApplication (for being
able to use Signal/Slots).

What are the technical reasons why you should also not do that, if
there are? ... because static variables do not count in that scenario,
at least I think so.

Thanks
Lorenz