Hello sir,

The question is regarding c++ class Hierarchy Audio 10. I have tried a small program to print the address of multiple class hierarchy below is the snapshot.

class A
{
public:
A() :a(1), b(2), c(3) {}
int a;
int b;
int c;
};
class B
{
public:
B() :a(10), b(20), c(30) {}
int a;
int b;
int c;
};
class C :public A, public B
{
public:
C() :a(100), b(200), c(300) {}
int a;
int b;
int c;
};

void funcA(A* addr)
{
//int addr = convert((int)a);
std::cout << “funcA :” << addr << std::endl;
std::cout << “funcA A* data:” << addr->c << std::endl; //compiler doing implicit typecasting incase &c
std::cout << “funcA C* data:” << ((C*)addr)->c << std::endl << std::endl;

std::cout << std::endl;
}

void funcB(B* addr)
{
//int addr = convert((int)b);
std::cout << “funcB :” << addr << std::endl;
std::cout << “funcB C*:” << (C*)addr << std::endl;
std::cout << “funcB B* data:” << addr->c << std::endl;
std::cout << “funcB C* data:” << ((C*)addr)->c << std::endl << std::endl;

}

void funcC(C* addr)
{
//int addr = convert((int)c);
std::cout << “funcC C*:” << addr << std::endl;
std::cout << “funcC A*:” << (A*)addr << std::endl;
std::cout << “funcC B*:” << (B*)addr << std::endl <;

std::cout << “funcC C* data” << addr->c << std::endl;
}

int main()
{

A a;
B b;
C c;

std::cout << &c << std::endl;
funcC(&c); //Invocation 1
funcA(&c); // Invocation 2
funcB(&c); // Invocation 3

return 0;
}

output >>

0078F8EC
funcC C*:0078F8EC
funcC A*:0078F8EC
funcC B*:0078F8F8
funcC C* data 300

funcA :0078F8EC
funcA A* data:3
funcA C* data:300

funcB :0078F8F8
funcB C*:0078F8EC
funcB B* data:30
funcB C* data:300

In invocation 1 on object c , both A* and C* are pointing to a same address, how does compiler interprets internally to invoke C’s subobject data from Composite object.

In invocation 2 on object c, though both A * and C * holding same address , How does typecasting addr to (C*), able to print C’s subobject data.

In invocation 3 I see the delta change of 12 byte is added  while doing implicit typecasting t0 B* , and again doing explicit typecasting t0 C * having the same address as A * how is compiler is able to print C’s data.

How compiler knows exactly to which member of composite object to invoke, when explicit typecasting is done.

Regards

G V Siddesh