From @wedsonaf #603 (comment):

One aspect of this PR that I'm not completely happy with is that we're returning a u32 without any mention of the meaning. So users need to read to the Rust code to figure out that it refers to f_flags, then the C code to figure out what those refer to, then they'll be forced to use constants in bindings to check specific flags.

So in addition to the winding path to find the actual flags, there is the problem that they are in a module that we intend to eventually make private.

For cases like this I've taken two different approaches, depending on whether the values can be ORed (which is the case here):

1. If the values are unique, I declare an enum (e.g., ExtraResult)
2. If they can be ORed, I declare a type and publish the constants in it (e.g., Type), then mention it in the documentation of the method (e.g., set_type).

Ideally we'd do something similar here.