C / C++ / MFC

class CCursorPos
{
public:

	CCursorPos()
	{
		invalidate();
	}

	CCursorPos(const CCursorPos& pos)
	{
		*this = pos;
	}

	BOOL isValid() const
	{
		return (m_posItem!=NULL && m_textPos.x > -1 && m_textPos.y > -1);
	}

	CCursorPos& operator=(const CCursorPos& pos)
	{
		ASSERT(pos.isValid());
		setCursor(pos.getItem(),pos.getTextPoint());
		return *this;
	}

	BOOL operator==(const CCursorPos& pos) const
	{
		ASSERT(isValid());
		ASSERT(pos.isValid());

		return (getItem() == pos.getItem() && 
			getTextPoint() == pos.getTextPoint());
	}

	BOOL operator!=(const CCursorPos& pos) const
	{
		return !(*this == pos);
	}

	POSITION getItem() const
	{
		ASSERT(isValid());
		return m_posItem;
	}

	const CPoint& getTextPoint() const
	{
		ASSERT(isValid());
		return m_textPos;
	}

	void invalidate()
	{
		m_textPos.x = m_textPos.y = -1;
		m_posItem = NULL;
	}

	void setCursor(const POSITION& pos, const CPoint& ptText)
	{
		m_textPos = ptText;
		m_posItem = pos;
		ASSERT(isValid());
	}

protected:

	CPoint m_textPos;		// in view coordinates
	POSITION m_posItem;
};

........

class COutlineTextView
{
.....
CCursorPos m_selStart, m_selEnd;
std::vector<POSITION> m_selection;

....
};

void COutlineTextView::prepareSelBounds()
{
      if (m_selection.size() > 0){
		m_selection.clear();
	}

       .....

	POSITION pos = m_selStart.getItem();
	while(pos != NULL && pos != m_selEnd.getItem())
	{
		m_selection.push_back(pos);                 //CRASH HERE  !!!!!!
		pos = getOutline()->getNext(pos);
	}

	ASSERT(pos);
	m_selection.push_back(m_selEnd.getItem());
       ...
}