/in/foo.cc: In function 'void sch(int, int)':
/in/foo.cc:9:18: warning: iteration 8 invokes undefined behavior [-Waggressive-loop-optimizations]
   int nx = x+dx[i], ny = y+dy[i];
              ~~~~^
/in/foo.cc:8:21: note: within this loop
  for (rint i = 0; i <= 8; ++i) {
                   ~~^~~~