/in/foo.cc: In function 'int Sum(std::__cxx11::string)':
/in/foo.cc:9:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<s.length();i++)
                 ~^~~~~~~~~~~
/in/foo.cc: In function 'int Scmp(std::__cxx11::string, std::__cxx11::string)':
/in/foo.cc:21:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(i=0;i<s2.length();i++)  
             ~^~~~~~~~~~~~
/in/foo.cc: In function 'int Sum(std::__cxx11::string)':
/in/foo.cc:13:12: warning: 'sum' may be used uninitialized in this function [-Wmaybe-uninitialized]
     return sum;
            ^~~