adding two multiple inheritance examples

lectures/26_inheritance/multiple_inheritance2.cpp

@@ -0,0 +1,79 @@
+#include <iostream>
+
+// diamond inheritance
+// Address of A in B, in C, in D are the same, because there is only one copy.
+
+class A
+{
+public:
+	A(int a) : a(a) {}
+protected:
+	int a;
+};
+
+// virtual inheritance: declare A as the virtual base class
+// in virtual inheritance, B contains a pointer to the shared instance of A
+class B: virtual public A
+// class B: public A
+{
+public:
+	B(int a) : A(a) {}
+	void print(){
+		std::cout << "Address of A in B: " << reinterpret_cast<void*>(static_cast<A*>(this)) << std::endl;
+	}
+};
+
+// virtual inheritance: declare A as the virtual base class
+// in virtual inheritance, C contains a pointer to the shared instance of A
+class C: virtual public A
+// class C: public A
+{
+public:
+	C(int a) : A(a) {}
+	void print(){
+		std::cout << "Address of A in C: " << reinterpret_cast<void*>(static_cast<A*>(this)) << std::endl;
+	}
+};
+
+// D has a single shared instance of the virtual base class (A), regardless of how many times it appears in the hierarchy.
+// Due to virtual inheritance, there is a single shared instance of A within the D object.
+// This helps in avoiding the "diamond problem" and ensures that there is only one copy of the shared base class.
+class D: public B, public C
+{
+public:
+	D(int a): B(a), C(a), A(123) {}
+	// D(int a): B(a), C(a), A(a) {}
+
+	void print(){
+		// reference to ‘a’ is ambiguous
+		std::cout << "a is " << a << std::endl;
+		// std::cout << "a is " << C::a << std::endl;
+		//
+		B::print();
+		C::print();
+		std::cout << "Address of A in D: " << reinterpret_cast<void*>(static_cast<A*>(this)) << std::endl;
+		std::cout << "Address of B in D: " << reinterpret_cast<void*>(static_cast<B*>(this)) << std::endl;
+		std::cout << "Address of C in D: " << reinterpret_cast<void*>(static_cast<C*>(this)) << std::endl;
+	}
+};
+
+int main(){
+	D* dObject_p = new D(1);
+	dObject_p->print();
+
+	D dObject(2);
+	std::cout << sizeof(int) << std::endl;
+	// size of dObject = 4 (A) + 8 (pointer in B)+ 8 (pointer in C) + padding
+	std::cout << sizeof(dObject) << std::endl;
+
+	// release memory
+	delete dObject_p;
+
+	// Print sizes and addresses
+	std::cout << "Size of A: " << sizeof(A) << " bytes" << std::endl;
+	std::cout << "Size of B: " << sizeof(B) << " bytes" << std::endl;
+	std::cout << "Size of C: " << sizeof(C) << " bytes" << std::endl;
+	std::cout << "Size of D: " << sizeof(D) << " bytes" << std::endl;
+
+	return 0;
+}