/in/foo.c: In function 'main':
/in/foo.c:32:12: warning: zero-length gnu_printf format string [-Wformat-zero-length]
     printf("");
            ^~
/in/foo.c:35:12: warning: zero-length gnu_printf format string [-Wformat-zero-length]
     printf("", n1);
            ^~
/in/foo.c:41:12: warning: zero-length gnu_printf format string [-Wformat-zero-length]
     printf("");
            ^~
/in/foo.c:44:12: warning: zero-length gnu_printf format string [-Wformat-zero-length]
     printf("", n2);
            ^~
/in/foo.c:57:16: warning: zero-length gnu_printf format string [-Wformat-zero-length]
         printf("");
                ^~
/in/foo.c:64:16: warning: zero-length gnu_printf format string [-Wformat-zero-length]
         printf(""); 
                ^~