passing object to plugin

[folibis]

the code compiles without problem, as you can see it is linker error;
and plugin implementation file include header declaring Conf.h

I can define
void Lib1::init(QObject * ptr)
as
void Lib1::init(Conf * ptr)

but it still say "undefined reference to `Conf::getValue(int)'"

[d_stranz]

You have an undefined reference because even though your plugin knows what a Conf class looks like (which means it can compile the code), it doesn't have any idea how to get the Conf instance to do anything, because you haven't linked in the object code that contains the Conf class implementation.

This is exactly what Chris was saying in his answer. Both the application and the plugin need to be linked against the Conf class object code if they need to use the objects. If all your plugin does is pass around pointers to Conf instances but never tries to call any Conf class methods, then you simply need the header file so it can be compiled. But it looks like you expect your plugins to be able to use the Conf pointers, so you will need all of then to link against the object code.

Either that, or put the Conf object code in a DLL and link all of your apps and plugins against that so you aren't duplicating code.