Question

I have the following structs

struct A 
{
   int i;
   A() { i = 0; }
   A(int _i) : i(_i) {}
   virtual void f() { cout << i; }
};



struct B1 : virtual A {
   B1() : A(1) { f(); }
   void f() { cout << i+10; }
};


struct B2 : virtual A {
   B2(int i) : A(2) { f(); }
};


struct C : B1, B2 {
   C() : B2(3) {}
};

please explain why the following code prints 100: (10+0)

 C* c = new C();

I think it should print 1111:
first A() : i = 0
then B1() : i = 1 and prints B1::f() – 11
then B2() : prints prints B1::f() – 11

Where I go wrong?

Thanks

Answer 1

Due to the inheritance, the C object “contains” a B1 object and a B2 object. Both the B1 and the B2 object “contain” an A object, but since you have virtual inheritance of A, you only have one A object in each C object, not two. This single A object is initialized using A’s default constructor.