Why C++ virtual function defined in header may not be compiled and linked in vtable?

Question

Situation is following. I have shared library, which contains class definition -

QueueClass : IClassInterface
{
   virtual void LOL() { do some magic}
}
         


        

Answer 1

Functions defined in header files are in-lined on usage. They're not compiled as part of the library; instead where the call is made, the code of the function simply replaces the code of the call, and that is what gets compiled.

So, I'm not surprised to see that you are not finding a v-table entry (what would it point to?), and I'm not surprised to see that moving the function definition to a .cpp file suddenly makes things work. I'm a little surprised that creating an instance of the object with a call in the library makes a difference, though.

I'm not sure if it's haste on your part, but from the code provided IClassInterface does not necessarily contain LOL, only QueueClass. But you're casting to a IClassInterface pointer to make the LOL call.