Is there any point in using `override` when overriding a pure virtual function?

Solution 1:

However, in the case of a pure virtual function, the compiler would throw an error if we used an incorrect signature in the Derived class

No, this compiles:

class Base {
  virtual void my_function() = 0;
};

class Derived : Base {
  void my_function(int);
//                 ^^^ mistake!
};

While this does not:

class Base {
  virtual void my_function() = 0;
};

class Derived : Base {
  void my_function(int) override;
};

error: void Derived::my_function(int) marked override, but does not override

The error you're talking about only occurs when instantiating Derived - override allows you to catch the mistake earlier and makes the definition of Derived clearer/more readable.

Solution 2:

Yes, it is a good idea to use override keyword consistently as a defensive practice.

Consider a redesign when the author of the Base decides that my_function should no longer be a pure virtual, and also that it should take a new parameter. With override in place the compiler will catch this problem; without an override your Derived class would continue to compile.