Question

Look at this example

class base {
public:
    int m1;
    base() {
        m1 = 5;
    }
};

class der:  public base  {
public:
    int m1;
    der() {
        m1 = 6;
    }
};

int main() {
    der d;
    cout << d.m1;   
    return 0;
}

Here size of object d is 8 byte, which is allocated for 2 m1(one for base class and other for derive class). What is the mechanism to resolve d.m1?

Answer 1

The m1 in der hides the name of base‘s m1, so any access to m1 via a der object gets you that instance’s der::m1. You can access base::m1 in der like this:

class der:  public base  {
public:
    int m1;
    der() {
        m1 = 6;
        base::m1=7; // access base object's m1 inside der
    }
};

And you can access the base object thus:

der d;
d.base; // base object
std::cout << d.base::m1 >> "\n"; // access base object's m1 outside of der (if allowed)