Description of problem:

I attempted to build ocaml-lambda-term (as part of packaging utop; I'm simultaneously working on that and opam) on Fedora 26. lwt is a dependency.

I tried to build lambda-term 1.10.1, as it claims to support lwt >= 2.4.0, so it should work fine with our version of lwt: http://opam.ocaml.org/packages/lambda-term/lambda-term.1.10.1/

(I previously attempted to build lambda-term 1.11, which is the latest release, and had the same issue. But it claims to require a newer lwt).

The build mostly succeeds, except this happens when linking:

+ /usr/bin/ocamlfind ocamlopt -g -I src -linkpkg -package lwt -package lwt.react -package lwt.unix -package zed src/lambda-term.cmxa examples/events.cmx -o examples/events.native
File "_none_", line 1:
Error: Files /usr/lib64/ocaml/lwt/lwt-unix.cmxa
       and /usr/lib64/ocaml/unix.cmxa
       make inconsistent assumptions over implementation Unix
Command exited with code 2.

This seems concerning.

Note that if I try to build lambda-term on Fedora 25, it works without incident. Since the version of lwt is the same across both, perhaps there's some compatibility issue between the version of lwt we're shipping and ocaml 4.04?

Version-Release number of selected component (if applicable): 2.5.0-8.fc26

How reproducible: Always.


Steps to Reproduce:
1. Install ocaml-lwt-devel, ocaml-camomile-devel, ocaml-ocamldoc, ocaml-ocamlbuild.
2. Install ocaml-zed; I have submitted a review request for it here: https://bugzilla.redhat.com/show_bug.cgi?id=1481913 [1], and for F26 a RPM is available from this copr repository: https://copr.fedorainfracloud.org/coprs/tc01/ocaml-utils/.
3. Grab the 1.10.1 lambda-term sources (https://github.com/diml/lambda-term/archive/1.10.1.tar.gz) and extract them.
4. ./configure; make

Actual results: Build fails with the error message above.

Expected results: Build succeeds (or at least, gets past this step).

Additional info:

[1] Incidentally, I noticed the comment in the lwt spec about jbuilder. opam now needs jbuilder to compile, as does ocaml-zed, so while working on all this I submitted a spec for jbuilder too: https://bugzilla.redhat.com/show_bug.cgi?id=1481912. I imagine updating to newer lwt would solve this issue.