/in/foo.cc: In function 'int main()':
/in/foo.cc:5:17: warning: unused variable 'c' [-Wunused-variable]
    5 |         int a,b,c,d;
      |                 ^
/in/foo.cc:5:19: warning: unused variable 'd' [-Wunused-variable]
    5 |         int a,b,c,d;
      |                   ^