C / C++ / MFC

class B
{
public:
    B()
    {
        a=100;
    }
    int a;
};

class D : public B
{
public:
    D()
    {
        b=200;
    }
    int b;
};

int _tmain(void)
{
    //Create derived object and assign it to base variable
    B* b1 = new D();
    //copy object in base variable to another base variable
    B* b2 = b1;
    //copy copied base variable to derived variable
    D* d = static_cast<D*>(b2);
    //try accessing a member available only in D
    printf("%d",d->b);    
    //worked fine - printed 200 as expected
    delete b1;
    return 0;
}

class Base{
public:
  virtual Base * clone()const=0; // =0 if no implementation is given in the Base class.
...
};
 
class Derived: public Base
{
public:
  virtual Base * clone()const
  {
    return new Derived(*this);
  }
};

char sqlstr[512];<br />
sprintf(sqlstr,"insert into tablename(id,ip) values ('%s','%s')",myid,myip);