I don't have a general answer for finding such dependencies, but in the list you have it seems there is at least batteries that depends on Unix.

Le 13 juin 2015 09:22:28 UTC+02:00, Tim Cuthbertson <tim@gfxmonk.net> a écrit :
>Hi all,
>
>I'm attempting to convert an existing (reasonably small) HTTP server
>written in OCaml to run on mirage's xen backend. I've gotten the
>compiler
>reasonably happy by replacing uses of Unix / Lwt_unix with appropriate
>mirage-compatible modules. But when it comes to link time, it seems
>that my
>application is still indirectly depending on Unix:
>
>+ ocamlbuild -quiet -cflag -warn-error -cflag +a-3 -build-dir
>[...]/_build/mirage-xen -use-ocamlfind -lflags
>-g,-linkpkg,-dontlink,unix
>main.native.o
>+ ocamlfind ocamlopt -g -linkpkg -dontlink unix -output-obj -syntax
>camlp4o
>-package 'fat-filesystem, io-page, mirage-block-xen.front, batteries,
>yojson, safepass, sha, lwt, lwt.syntax, mirage-console.xen,
>mirage-types,
>mirage-types.lwt, mirage-net-xen, mirage-types,cohttp,cohttp.lwt,
>mirage-http, lwt, mirage.runtime,
>tcpip.stack-direct,tcpip.stack-socket,mirage-clock-xen,conduit.mirage'
>src/passe.cmx src/passe_server.cmx src/unikernel.cmx main.cmx -o
>main.native.o
>File "_none_", line 1:
>Error: No implementations provided for the following modules:
>         Unix referenced from
>/home/tim/.opam/mirage_4_01_0/lib/lwt/lwt-unix.cmxa(Lwt_engine),
>         /home/tim/.opam/mirage_4_01_0/lib/lwt/lwt-unix.cmxa(Lwt_unix),
>
>/home/tim/.opam/mirage_4_01_0/lib/ipaddr/ipaddr_unix.cmxa(Ipaddr_unix)
>Command exited with code 2.
>
>I can't figure out why those modules are being linked in, though. I
>have
>grepped all files in _build/mirage-xen/**/*.ml.depends (as well as my
>own
>source code), and nothing in there matches "unix", nor mentions any of
>the
>modules listed above. The only lwt_* matches are:
>
>Cohttp_lwt_body
>Lwt_mutex
>Lwt_stream
>
>Which all seem like they shouldn't depend on unix either directly or
>indirectly.
>
>Is there some way to see a tree / list of "what module in my source
>code is
>transitively depending on Unix, and via what modules is that dependency
>inherited?" Or even if there's no way to see a tree, is there a way to
>do
>it one step at a time (e.g "what is depending directly on Lwt_unix",
>then
>repeat the process for those modules listed until I see something that
>surprises me)
>
>Failing that, does anyone have tricks for weeding indirect `Unix` usage
>out
>of a codebase which is not directly using it?
>
>Thanks,
> - Tim Cuthbertson
>
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-- 
Simon