code: public void clearLocalSlots(int start, int len)
    {
  
      start += _currentFrameBottom;
  
      System.arraycopy(m_nulls, 0, _stackFrames, start, len);
    }
docs: Use this to clear the variables in a section of the stack.  This is
  used to clear the parameter section of the stack, so that default param
  values can tell if they've already been set.  It is important to note that
  this function has a 1K limitation.
  
  @param start The start position, relative to the current local stack frame.
  @param len The number of slots to be cleared.