What are the advantages and disadvantages of using virtual tables?

Virtual tables (vtable) are a mechanism in object-oriented programming used to implement dynamic polymorphism (virtual functions).

Advantages:

• Allow calling methods of derived classes through a pointer or reference to the base class.
• Provide flexibility and extensibility of code.
• Simplify support and addition of new classes without modifying existing code.

Disadvantages:

• Slight decrease in performance due to an additional level of indirect function calls.
• Increase in object size due to the pointer to the virtual table.
• Complexity of implementation and understanding for beginners.

Example in C++:

class Base {
public:
    virtual void foo() { std::cout << "Base" << std::endl; }
};

class Derived : public Base {
public:
    void foo() override { std::cout << "Derived" << std::endl; }
};

Base* b = new Derived();
b->foo(); // Calls Derived::foo thanks to vtable