Polymorphism via indirect virtual dispatch basically means you want to treat different kinds of objects differently via the same interface. If you take OOP as programming with objects, it most definitely is doing OOP; if you take OOP as being Java or some other more specific definition, then it isn’t.

When you implement an extended jump table (a table set that extends an existing table def) in C, that is also just inheritance.

There is a good reason the first C++ compiler was just implemented as a bunch of macros in C.