When its a table of function pointers used for dynamic dispatch, to me it's a vtable. I don't care about their type signatures as long as they logically belong to the object in question.
You seem to have a different very narrow definition of vtables, so the discussion is kind of useless.
X is Y used in Z. Does that mean X is not Y when it is not used in Z? A knife is a sharp object used to cut meat. How do I call the thing to cut fish?
Yes, I see how you can parse the definition your way, I didn't thought about that before introducing it.
> since it is an ADT, not anything object oriented
Yes, they have large overlap. To my understanding, the difference is, that OOP has inheritance and an ADT can be provided by the big god object. The latter I would refrain to call OOP, although it can be argued it still is.
I think our real discussion here is, whether a function entry that doesn't take an argument of the object type precludes it being a vtable. To me it is as long as this function is supposed to be a method of a single object and not for all objects in general, i.e. a global function.
I agree.
> If you omit the this pointer, you cannot do inheritance that uses the this pointer in an override
Yes, but:
> If you omit the this pointer, you cannot do inheritance
You can absolutely do inheritance when the child implementation doesn't need a this pointer. You need the this pointer to read/write values of the instance not to know which types it is.
Let me give you an example:
class Vehicle {
virtual unsigned int get_number_of_wheels () = 0;
};
class Car: Vehicle;
class Bicycle: Vehicle;
unsigned int Car::get_number_of_wheels () { return 4; }
unsigned int Bicycle::get_number_of_wheels () { return 2; }
This is exactly was is going on with check_flags(). The signature is inherited from a (virtual) base class. Part of that interface contract is that the allowed values are only depended upon the file object's type and not on it's values. You choose the implementation invoked at object construction, if it would need a this pointer, it means that the values returned can change during the lifetime of the object.
The following commands manipulate the flags associated with a file descriptor. [...]
F_SETFD (int)
Set the file descriptor flags to the value specified by arg.