Diamond problem in CPP


 Diamond problem explained


The basic scenario

a. Suppose P is the base class.

b .Class Q and R inherits from class P.

c. Class S inherits from both Q and R.



Now, if P has a member (like a variable or function), and S tries to access it, ambiguity arises: should it use the version inherited via Q or the one via R?


CPP Program:

#include <iostream>

using namespace std;


class A {

public:

    void show() { cout << "A::show" << endl; }

};


class B : public A { };


class C : public A { };


class D : public B, public C { };


int main() {

    D obj;

    obj.show(); // ❌ Error: request is ambiguous

   

}


How we will solve it:

C++ solve this problem using virtual function which ensures that only one copy of the base class is shared.

Solved :

#include <iostream>

using namespace std;


class A {

public:

    void show() { cout << "A::show" << endl; }

};


class B : virtual public A { };


class C : virtual public A { };


class D : public B, public C { };


int main() {

    D obj;

    obj.show(); // ✅ No ambiguity

}






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