OCaml dependencies encode a MD5 hash across the code in the library. eg:
$ ocamlobjinfo /usr/lib64/ocaml/unix.cma | grep Unix Unit name: Unix e6d191b089c68976347fa6524bb28048 Unix
This is encoded into the Fedora dependency, which is necessary because the OCaml compiler checks the hash and will complain (fail to compile code) if the hash between libraries is not in agreement:
$ rpm -q --provides ocaml | grep 'ocaml(Unix)' ocaml(Unix) = e6d191b089c68976347fa6524bb28048
Note this hash applies to OCaml bytecode libraries, which we don't really use in Fedora, but it was convenient to encode this since it doesn't change except if the source code of the library changes.
So far so good ...
However Fedora recently-ish started also generating a hash for native code OCaml libraries. The change was actually made in RPM here:
https://github.com/rpm-software-management/rpm/issues/913
In theory these hashes are also supposed to be stable - eg. a simple rebuild of the package should not change the hash. Unfortunately for some reason that I don't understand they were changed in the mass rebuild. eg. compare ocamlx(Dynlink) between:
https://koji.fedoraproject.org/koji/rpminfo?rpmID=23061389 (before) https://koji.fedoraproject.org/koji/rpminfo?rpmID=24866739 (after rebuild)
Notice that ocaml(Dynlink) (bytecode) is the same, but ocamlx(Dynlink) (native code) changed.
I tried to reproduce this locally, by recompiling ocaml and changing the release number, upgrading gcc, and a few other things, but I couldn't get the dependencies to change at all.
So ... I don't know.
It's a bit of a mess at the moment, and some, possibly many, ocaml-* packages in Rawhide may be uninstallable.
We're expecting that ocaml 4.12.0 will be released very soon - perhaps as soon as later this week - and I will do a mass rebuild of all the OCaml packages which will as a side effect fix this.
In the meantime I will rebuild packages on demand if people encounter problems (in fact, already started that, see https://bugzilla.redhat.com/show_bug.cgi?id=1923853)
Rich.