/in/foo.cc: In function 'int num(long long int, long long int)':
/in/foo.cc:12:9: warning: 'ret' may be used uninitialized in this function [-Wmaybe-uninitialized]
  return ret;
         ^~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:12:9: warning: 'ret' may be used uninitialized in this function [-Wmaybe-uninitialized]
  return ret;
         ^~~
/in/foo.cc:6:12: note: 'ret' was declared here
  long long ret;
            ^~~