/in/hotel-mt.c: In function 'check_out':
/in/hotel-mt.c:144:16: error: unused variable 'f' [-Werror=unused-variable]
     visitor_t *f=v;
                ^
/in/hotel-mt.c: In function 'show_room':
/in/hotel-mt.c:156:12: error: comparison with string literal results in unspecified behavior [-Werror=address]
     if(type=="single"){
            ^~
/in/hotel-mt.c:158:18: error: comparison with string literal results in unspecified behavior [-Werror=address]
     }else if(type=="double"){
                  ^~
/in/hotel-mt.c:160:18: error: comparison with string literal results in unspecified behavior [-Werror=address]
     }else if(type=="family"){
                  ^~
/in/hotel-mt.c:162:18: error: comparison with string literal results in unspecified behavior [-Werror=address]
     }else if(type=="dorm"){
                  ^~
cc1: all warnings being treated as errors