How to hack the virtual table?

Question

I would like to know how to change the address of Test which is in the virtual table with that of HackedVTable.

void HackedVtable()
{
           


        

Answer 1

void HackedVtable()
{
    cout << "Hacked V-Table" << endl;
}

class Base
{

public:
       virtual Test()  { cout <<"base";    }
       virtual Test1() { cout << "Test 1"; }
       void *prt;
       Base(){}
};

class Derived:public Base
{
    public: 
           Test() 
           {
                   cout <<"derived";
           }
};

typedef void (*FUNPTR)();
typedef struct
{
   FUNPTR funptr;
} VTable;


int main()
{

    Base b1;
    Base *b1ptr = &b;

    VTable vtable;
    vtable.funptr = HackedVtable;

    VTable *vptr = &vtable;
    memcpy ( &b1, &vptr, sizeof(long) );

    b1ptr->Test();

    //b1.Test(); // how to change this so that HackedVtable() should be called instead of Test()

    return 0;
}