An entry flag, name in known means that the bit(s) in flag is (are) called name; i.e. if bit_and flags flag = flag, then the bit(s) is (are) set and name will appear in sexp_of_t flags. known is only used to make sexp_of_t's output human readable.

The flags in the output of sexp_of_t will occur in the same order as they appear in known.

It is allowed to have a single flag with multiple bits set.

It is an error if different flags intersect, and allow_intersecting = false.

If remove_zero_flags, then all flags with value zero will be automatically removed from known. If not remove_zero_flags, then it is an error for known to contain any flags with value zero.

About this existence of this option: it seems better to make it an option here rather than do the filtering at the functor call site. It also makes clear to callers that they need to think about zero flags, and clear what they can do if they encounter them.

allow_intersecting says whether to allow intersecting known flags. It is common to do allow_intersecting = false, however in some situations, e.g. Unix open flags, the flags intersect.

should_print_error says whether to print an error message if there is an error in the known flags. It is typical to use should_print_error = true because Flags.Make is applied at the module level, where the exception raised isn't displayed nicely.