../src/devices/wifi/minstrel-wifi-manager.cc:528:42: error:
      comparison of unsigned expression < 0 is always false
      [-Wtautological-compare]
          if (idx >= m_nsupported || idx < 0)
                                     ~~~ ^ ~

Here, idx is declared as uint32_t, and can never be <0. Hence the idx < 0 clause can be safely removed.