Plugin with non-virtual functions?

I want to write some plugins for my application with non-virtual functions. In the documentation for the plugins system [qt-project.org] it says “Define a set of interfaces (classes with only pure virtual functions) used to talk to the plugins.” So i think it’s not possible to have non-virtual functions in a plugin. Is there antoher way of implementing a plugin interface with some code in it? Do i really have to write the same in every plugin i write? Thanks in advance!