libavutil/rc4.c:42: error: Uninitialized Value
  The value read from state[_] was never initialized.

libavutil/rc4.c:42:9: 
40.     x = 1; y = state[1];
41.     while (datalen-- > 0) {
42.         uint8_t sum = state[x] + state[y];
            ^
43.         FFSWAP(uint8_t, state[x], state[y]);
44.         *data++ ^= state[sum];
