diamond_problem_virtual_inheritance.cpp

#include <iostream>
#include <string>
/*

Ref: https://www.sandordargo.com/blog/2020/12/23/virtual-inheritance


               base
            /        \
         superA     superB
            \        /
               child
*/

namespace normalInheritance {
class base {
public:
  base() { std::cout << "base constructor" << std::endl; }
};

class superA : public base {
public:
  superA() { std::cout << "superA constructor" << std::endl; }
};

class superB : public base {
public:
  superB() { std::cout << "superB constructor" << std::endl; }
};

class child : public superA, superB {
public:
  child() { std::cout << "child constructor" << std::endl; }
};

} // namespace normalInheritance

namespace virtualInheritance {
class base {
public:
  base() { std::cout << "base constructor" << std::endl; }
};

class superA : virtual public base {
public:
  superA() { std::cout << "superA constructor" << std::endl; }
};

class superB : virtual public base {
public:
  superB() { std::cout << "superB constructor" << std::endl; }
};

class child : public superA, superB {
public:
  child() { std::cout << "child constructor" << std::endl; }
};

} // namespace virtualInheritance

int main() {
  std::cout << "===============Normal Inheritance===============" << std::endl;
  { normalInheritance::child childObject; }

  /*
  "virtual" keyword make the classes superA and superB as virtual base classes
  to avoid two copies of base in child class.
  */

  std::cout << "===============Virtual Inheritance===============" << std::endl;
  { virtualInheritance::child childObject; }
}