On Sat, Jun 13, 2015 at 10:07 PM, Török Edwin <edwin+ml-ocaml@etorok.net> wrote:
On 06/13/2015 10:22 AM, Tim Cuthbertson wrote:
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?
'ocamlfind query -r' can be useful, in your case:
$ ocamlfind query -r -p-format 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 | grep unix
unix
lwt.unix
ipaddr.unix
conduit.lwt-unix
io-page.unix
Drop cohttp.lwt, tcpip.stack-direct, tcpip.stack-socket (use tcpip.xen? and you already have mirage-http and cohttp.lwt-core), and then:
$ ocamlfind query -r -p-format 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 mirage-http lwt mirage.runtime mirage-clock-xen conduit.mirage | grep unix
unix
Best regards,
--Edwin
Thanks for the advice, that has gotten me much further.
tcpip-stack-direct still seems necessary, but *-socket isn't. I notice
`unix` is still in the output
after removing these modules (which
seems like a bad thing), and yet it successfully compiles
main.native.o now. Perhaps that is related to:
On Sat, Jun 13, 2015 at 11:06 PM, Simon Cruanes
<simon.cruanes.2007@m4x.org> wrote:
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.
I thought so too, but I was hoping that I can use toplevel modules
(specifically BatList and BatString), so that even though the
"batteries" package depends on Unix, those individual modules I'm
using don't. In which case the Unix dependency won't actually be
needed or referenced. But perhaps the dependencies aren't that
fine-grained?
(I should probably drop the Batteries dependency
since I'm using so
little, but it's used more heavily in non-server parts of the same
codebase)