foo.cc: In function 'int main()':
foo.cc:5:9: warning: unused variable 'a' [-Wunused-variable]
     int a, b, c;
         ^
foo.cc:5:12: warning: unused variable 'b' [-Wunused-variable]
     int a, b, c;
            ^
foo.cc:5:15: warning: unused variable 'c' [-Wunused-variable]
     int a, b, c;
               ^

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。