#include <unistd.h>#define STRINGIFY(x) #x#define TOSTRING(x) STRINGIFY(x)#define CURRENT_LOCATION __FILE__ ":" TOSTRING(__LINE__)#define err()                         \{                                     \  _fail("at " CURRENT_LOCATION " ");  \}#define mb() asm volatile ("" : : : "memory")extern void pass(void);extern void _fail(char *reason);