Compiling a dll (TEMPLATE =LIB) with MSVC2012 leads to unresolved external symbol

[d_stranz]

Yes, this will work. I presume that at some point in loading the plugin, you call some type of "initialize()" method and pass in a pointer to a concrete instance of the virtual class, right?

If you look at the Qt Creator architecture, the main application is pretty much just a plugin loader. All of the functionality of Creator is moved into plugin DLLs, one of which (Core) is required to be present. The other plugins ask Core to do things for them, through virtual interfaces. Your implementation basically merges Core aand the main app together.

[maitai]

Yes, this will work. I presume that at some point in loading the plugin, you call some type of "initialize()" method and pass in a pointer to a concrete instance of the virtual class, right?

Yes exactly. I load the plugin from my main widget (which is a MainWindow, derived from MainWindowInterface, itself derived from QMainWindow), and do something like
pluginLoader->instance()->init((MainWindowInterface *)this);

After that the plugin has a concrete instance of my widget, and can use whatever methods or even slots that are defined as virtual in MainWindowInterface.h. That way I don't need to link it against MainWindow's actual code.