Unix.getaddrinfo doesn't report errors

[MisterDA]

getaddrinfo (POSIX, Windows) errors are not set into errno, but returned to the caller. The implementation of Unix.getaddrinfo doesn't report errors to the OCaml side and returns an empty list instead.
Errors codes returned from getaddrinfo are distinct from errno errors and likely shouldn't be mapped (contrary to, for examples, error code of the POSIX threads API). Maybe a distinct Unix.addrinfo_error exception type should be added?
Note that on POSIX platforms, if EAI_SYSTEM is returned, then errno should be checked to report system errors (not specific to getaddrinfo). This would also mean raising a Unix.unix_error in this case.
Should these two points be considered? Is introducing an exception a breaking change, frowned upon? Another option would be to failwith a string, like in Unix.map_file.

The remarks also apply to getnameinfo and related. Error reporting has been missing since the introduction of IPv6 in OCaml 21 years ago, so that's probably not a hot topic.

[hannesm]

noteworthy to link to https://github.com/haesbaert/ocaml-getaddrinfo which as far as I remember does error reporting nicely.