/in/foo.cc: In function 'int main()':
/in/foo.cc:34:13: warning: iteration 18 invokes undefined behavior [-Waggressive-loop-optimizations]
   _a[i] = i * 123456789;
           ~~^~~~~~~~~~~
/in/foo.cc:33:20: note: within this loop
  for (int i = 0; i < N; i++) {
                    ^