Is the 'virtual' Keyword Redundant When Overriding Virtual Functions in C Derived Classes?

Virtual Functions in Derived Classes: Is the "virtual" Keyword Redundant?

In the context of C object-oriented programming, virtual functions play a crucial role in implementing polymorphism. When a derived class overrides a virtual function, it creates a new implementation without breaking the behavior of its base class.

Consider the following struct definition:

struct A {
    virtual void hello() = 0;
};

This struct declares a pure virtual function named hello(). Now, let's examine two approaches to overriding hello() in a derived struct B:

Approach #1 (with "virtual"):

struct B : public A {
    virtual void hello() { ... }
};

Approach #2 (without "virtual"):

struct B : public A {
    void hello() { ... }
};

At first glance, the only difference between these approaches is the presence or absence of the "virtual" keyword before the overridden hello() function. Does this make any functional difference?

Answer: No, there is no functional difference between these two approaches.

Despite the use of the "virtual" keyword in Approach #1, both approaches are equivalent and will produce the same behavior. The "virtual" keyword is redundant in this case because the hello() function is already declared as virtual in the base class A.

Therefore, when overriding virtual functions in derived classes, the "virtual" keyword can be omitted without affecting the functionality or semantics of the program. It is simply a matter of style and preference whether to use it or not.

The above is the detailed content of Is the 'virtual' Keyword Redundant When Overriding Virtual Functions in C Derived Classes?. For more information, please follow other related articles on the PHP Chinese website!