In C++, it is possible to create empty base classes. These empty base classes do not have any member variables or member functions. However, they can still have constructors.

Why use empty base classes?

Empty base classes can be used to inherit specific behavior or traits from a particular class without adding any additional member variables or functions. This can be useful in certain situations, such as when creating class hierarchies or implementing design patterns.

Constructors in empty base classes

Empty base classes can have constructors just like any other class in C++. The constructors in empty base classes can be used to initialize the inherited members or to perform any specific operations.

Here’s an example of how constructors can be defined in empty base classes:

class EmptyBase {
public:
    EmptyBase() {
        // Constructor implementation
    }
};

In the above example, EmptyBase is an empty base class with a default constructor.

Initialization of empty base class constructor

When initializing an empty base class constructor, the constructor of the derived class is responsible for initializing the base class constructor. This is done using the member initialization list in the derived class constructor.

class Derived : public EmptyBase {
public:
    Derived(int value) : EmptyBase(), m_value(value) {
        // Constructor implementation
    }

private:
    int m_value;
};

In the above example, the derived class Derived explicitly invokes the default constructor of the empty base class EmptyBase in the member initialization list.

Conclusion

Empty base classes in C++ allow us to inherit specific behavior without adding any extra member variables or functions. By defining constructors in empty base classes, we can customize the initialization process and perform any necessary operations.