-// Teach the compiler that some code path is unreacheable:
-#if defined(__has_builtin)
-# if __has_builtin(__builtin_unreachable)
-# define XBT_UNREACHABLE() __builtin_unreachable()
-# else
-# include <stdlib.h>
-# define XBT_UNREACHABLE() abort()
-# endif
-#elif (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5)
-# define XBT_UNREACHABLE() __builtin_unreachable()
-#else
-# include <stdlib.h>
-# define XBT_UNREACHABLE() abort()
-#endif
-