Inheritance and friendship

In C++, friendship is not inherited. If a base class has a friend function, then the function doesn’t become a friend of the derived class(es).

For example, following program prints error because show() which is a friend of base class A tries to access private data of derived class B.

#include <iostream> 
using namespace std; 
  
class A 
{ 
  protected: 
    int x; 
  public: 
    A() { x = 0;} 
  friend void show(); 
}; 
  
class B: public A 
{ 
  public: 
    B() : y (0) {} 
  private: 
    int y; 
  
}; 
  
void show() 
{ 
  B b; 
  cout << "The default value of A::x = " << b.x; 
  
  // Can't access private member declared in class 'B' 
  cout << "The default value of B::y = " << b.y; 
} 
  
int main() 
{ 
  show(); 
  getchar(); 
  return 0; 
} 

Thanks to Venki for the above code and explanation.

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above

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