code: def p_ifdef_else(p):
      
      global ENABLED
  
      p[0] = p[1] + p[2]
      p[0] += ['#line %i "%s"' % (p.lineno(3) + 1, CURRENT_FILE[-1])]
      ENABLED = IFDEFS[-1][0]
      IFDEFS.pop()
docs: ifdef : ifdefelsea ifdefelseb ENDIF