As you may have understood from the MyClass definition, it has defined the default constructor, copy constructor and destructor, an assignment operator, and sayHello() methods, as shown here:

//Definitions removed here to keep it simple 
class MyClass {
public:
      MyClass() { }  //Default constructor
      ~MyClass() { } //Destructor 
      MyClass ( const MyClass &objectBeingCopied ) {} //Copy Constructor 
      MyClass& operator = ( const MyClass &objectBeingAssigned ) { } //Assignment operator
      void sayHello();
}; 

The methods of MyClass have nothing more than a print statement that indicates the methods got invoked; they were purely meant for demonstration purposes. 

The main() function creates two auto_ptr smart pointers that point to two different MyClass objects, as shown here:

int main ( ) {

   auto_ptr<MyClass> ptr1( new MyClass() );
   auto_ptr<MyClass> ptr2( new MyClass() );

   return 0;

}

As you can understand, auto_ptr is a local object that wraps a raw pointer, not a pointer. When the control hits the return statement, the stack unwinding process gets initiated, and as part of this, the stack objects, that is, ptr1 and ptr2, get destroyed. This, in turn, invokes the destructor of auto_ptr that ends up deleting the MyClass objects pointed by the stack objects ptr1 and ptr2.

We are not quite done yet. Let's explore more useful functionalities of auto_ptr, as shown in the following main function: 

int main ( ) {

    auto_ptr<MyClass> ptr1( new MyClass() );
    auto_ptr<MyClass> ptr2( new MyClass() );

    ptr1->sayHello();
    ptr2->sayHello();

    //At this point the below stuffs happen
    //1. ptr2 smart pointer has given up ownership of MyClass Object 2
    //2. MyClass Object 2 will be destructed as ptr2 has given up its 
    //   ownership on Object 2
    //3. Ownership of Object 1 will be transferred to ptr2
    ptr2 = ptr1;

    //The line below if uncommented will result in core dump as ptr1 
    //has given up its ownership on Object 1 and the ownership of 
    //Object 1 is transferred to ptr2.
    // ptr1->sayHello();

    ptr2->sayHello();
   
    return 0;

}