How can you modify an object without calling member functions?

Question

At 3.10/10, the standard says:

An lvalue for an object is necessary in order to modify the object except that an rvalue of class type can also be used to

Answer 1

I can think of one way:

If your class exposes public member variables, you can assign directly to those member variables. For example:

class A
{
    public:
        int _my_var;
...
};

int main(int argc, char** argv)
{
    A *a = new C();
    a->_my_var = 10;
}

This is not a good programming style though - exposing a member variable as public isn't something I would advocate or even suggest.

Also, if you can do something really weird, such as directly writing some address in memory, an offset from the pointer to the class object - but why would you do that?