/in/foo.cc: In function 'int main()':
/in/foo.cc:2:31: warning: zero-length gnu_printf format string [-Wformat-zero-length]
 #define Q(A,B) case A:printf(B);break;
                               ^
/in/foo.cc:9:9: note: in expansion of macro 'Q'
         Q(3,"");
         ^