/in/foo.cc: In function 'std::__cxx11::string op2(int)':
/in/foo.cc:35:14: error: cannot convert 'std::__cxx11::string {aka std::__cxx11::basic_string<char>}' to 'int' in assignment
   num=op2(tmp);
              ^
/in/foo.cc:37:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^