A need for a copy constructor

    //point.h
    class Point {
    public:
        int  m_coord[ 2 ];
        int* m_ptr;

        Point() {
            m_coord[ 0 ] = -1;
            m_coord[ 1 ] = -1;
            m_ptr = m_coord;
        }
        
        void reset() {
            m_ptr[ 0 ] = 0;
            m_ptr[ 1 ] = 0;
            m_ptr = 0;
        }
    };//class Point

//main.cpp
#include <cassert>

void main()
{
    Point pt1;
    Point pt2;
    draw_segment( pt1, pt2 );

    assert( pt1.m_coord[ 0 ] == -1 );
    assert( pt1.m_ptr != 0 );
}

    //point.cpp
    void draw_segment( Point from, Point to )
    {
        // Draw a line:
        // ...
        // Then reset objects:
        from.reset(); // Hmm?..
        to.reset();
    }