/in/foo.cc: In function 'int Count(int)':
/in/foo.cc:23:9: warning: 'sum' may be used uninitialized in this function [-Wmaybe-uninitialized]
  return sum;
         ^~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:30:17: warning: 'sum' may be used uninitialized in this function [-Wmaybe-uninitialized]
  printf("%d", k);
                 ^