libavcodec/4xm.c:572: error: Uninitialized Value
  The value read from flag[_] was never initialized.

libavcodec/4xm.c:572:13: 
570. 
571.         for(node= j; up[node] != -1; node= up[node]){
572.             bits += flag[node]<<len;
                 ^
573.             len++;
574.             if(len > 31) av_log(f->avctx, AV_LOG_ERROR, "vlc length overflow\n"); //can this happen at all ?
