new/delete and DECLARE_DYNCREATE/DECLARE_DYNAMIC

// class CShape : public CObject
// class CCircle : public CShape
// class CRectangle : public CShape

CShape* CYourShapeTool::MakeCopy(CShape* pcSrcShape)
{
  ASSERT(pcSrcShape);

  CShape* pcResShape = STATIC_DOWNCAST(
    CShape, pcSrcShape->GetRuntimeClass()->CreateObject() // Default constuctor's call only
  );
  ASSERT(pcResShape);
  
  // Now you could call the virtual void CShape::Assign(const CShape* pcSrc),
  // overwritten by each class (CShape, CCircle, CRectangle) -
  // to copy the properties (class members) as well:
  pcResShape->Assign(pcSrcShape);
  
  return pcResShape;
}

void TestFunction()
{
  CYourShapeTool cTool;

  CCircle cCircle(10, 10, 5); // Non-default constructor's call
  CCircle* pcCopyCircle = STATIC_DOWNCAST(
    CCircle, cTool.MakeCopy(&cCircle) // Default constructor + Assign
  );
  delete pcCopyCircle;
  pcCopyCircle = NULL;

  CRectangle cRect(20, 20, 50, 50); // Non-default constructor's call
  CRectangle* pcCopyRect = STATIC_DOWNCAST(
    CRectangle, cTool.MakeCopy(&cRect) // Default constructor + Assign
  );
  delete pcCopyRect;
  pcCopyRect = NULL;
}