/in/foo.cc: In function 'int tohash(const string&)':
/in/foo.cc:15:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < str.size(); ++i) {
                  ~~^~~~~~~~~~~~
/in/foo.cc:17:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int j = i + 1; j < str.size(); ++j) {
                       ~~^~~~~~~~~~~~