/in/foo.cc: In function 'int main()':
/in/foo.cc:5:11: warning: unused variable 'b' [-Wunused-variable]
     int a,b,c,d;
           ^
/in/foo.cc:5:13: warning: unused variable 'c' [-Wunused-variable]
     int a,b,c,d;
             ^
/in/foo.cc:5:15: warning: unused variable 'd' [-Wunused-variable]
     int a,b,c,d;
               ^