/in/foo.cc: In function 'int main()':
/in/foo.cc:5:10: warning: unused variable 'c' [-Wunused-variable]
    5 |  int a,b,c,d;
      |          ^
/in/foo.cc:5:12: warning: unused variable 'd' [-Wunused-variable]
    5 |  int a,b,c,d;
      |            ^