-/* If "err" != 0, exit with an error message "msg" and clean up. If "msg" is a
- * NULL pointer, return generic "Details unknown". In any case, also print "err"
- * as the "internal error code". Also print errno if it is non-zero.
+/* If "err" == 0, do nothing. Else, clean up and exit with an error message that
+ * consists, first, of "msg" or (if "msg" is a NULL pointer) a generic "Details
+ * unknown, secondly of "err" as the "internal error code", and thirdly of errno
+ * if it is non-zero.
*/
extern void exit_err(uint8_t err, struct World * world, char * msg);