tst
#define tst(a, b) (*mode == 'r'? (b) : (a))
#define tst(a,b) (*mode == 'r'? (b) : (a))
#define tst(a, b) (*mode == 'r'? (b) : (a))
#define tst(a, b) (*mode == 'r'? (b) : (a))
static void tst(struct s *s)