/in/foo.cc: In function 'int main()':
/in/foo.cc:4:9: warning: unused variable 'b' [-Wunused-variable]
    4 |  char a,b,c,d;
      |         ^
/in/foo.cc:4:11: warning: unused variable 'c' [-Wunused-variable]
    4 |  char a,b,c,d;
      |           ^
/in/foo.cc:4:13: warning: unused variable 'd' [-Wunused-variable]
    4 |  char a,b,c,d;
      |             ^