/in/foo.cc: In function 'int main()':
/in/foo.cc:15:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  while(s.find(t,spos)!=-1)
        ~~~~~~~~~~~~~~^~~~
/in/foo.cc:13:6: warning: unused variable 'slen' [-Wunused-variable]
  int slen=s.size(), tlen=t.size(), ulen=u.size();
      ^~~~
/in/foo.cc:13:36: warning: unused variable 'ulen' [-Wunused-variable]
  int slen=s.size(), tlen=t.size(), ulen=u.size();
                                    ^~~~