#define _printf_attr_(a,b) __attribute__ ((format (printf, a, b)))
#define _sentinel_ __attribute__ ((sentinel))
#define _noreturn_ __attribute__((noreturn))
#define _printf_attr_(a,b) __attribute__ ((format (printf, a, b)))
#define _sentinel_ __attribute__ ((sentinel))
#define _noreturn_ __attribute__((noreturn))