Determine if slot 0 of the vtbl[] is reserved for something else. For class objects, yes, this is where the classinfo ptr goes. For COM interfaces, no. For non-COM interfaces, yes, this is where the Interface ptr goes.
0 vtbl[0] is first virtual function pointer 1 vtbl[0] is classinfo/interfaceinfo pointer
See Implementation
Determine if slot 0 of the vtbl[] is reserved for something else. For class objects, yes, this is where the classinfo ptr goes. For COM interfaces, no. For non-COM interfaces, yes, this is where the Interface ptr goes.