Threads library explicitely required to build with netsys

[Khady]

When using the netsys library (from ocamlnet), it is necessary to add the threads library to the libraries field BEFORE the netsys library. This is confusing because usually I think the order of the libraries doesn't matter. And when using ocamlbuild, there is no need to specify the dependency on threads.

The threads might be necessary because there is no requires(mt) += "threads" in the META file of netsys. But I didn't read in dune's documentation that the order in libraries is important.

$ dune build main.exe
    ocamlopt main.exe (exit 2)
(cd _build/default && /home/louis/.opam/frontend/bin/ocamlopt.opt -w @a-4-29-40-41-42-44-45-48-58-59-60-40 -strict-sequence -strict-formats -short-paths -keep-locs -g -o main.exe -I /home/louis/.opam/frontend/lib/bytes -I /home/louis/.opam/frontend/lib/netsys /home/louis/.opam/frontend/lib/ocaml/unix.cmxa /home/louis/.opam/frontend/lib/ocaml/bigarray.cmxa /home/louis/.opam/frontend/lib/netsys/netsys_oothr_mt.cmxa /home/louis/.opam/frontend/lib/netsys/netsys_oothr_mt_init.cmx /home/louis/.opam/frontend/lib/netsys/netsys.cmxa .main.eobjs/main.cmx)
File "_none_", line 1:
Error: No implementations provided for the following modules:
         Thread referenced from /home/louis/.opam/frontend/lib/netsys/netsys_oothr_mt.cmxa(Netsys_oothr_mt)
         Mutex referenced from /home/louis/.opam/frontend/lib/netsys/netsys_oothr_mt.cmxa(Netsys_oothr_mt)
         Condition referenced from /home/louis/.opam/frontend/lib/netsys/netsys_oothr_mt.cmxa(Netsys_oothr_mt)

Files to reproduce:

main.ml:

module N = Netsys

dune file I expected to work:

(executable (name main) (libraries netsys))

dune file with threads not working:

(executable (name main) (libraries netsys threads))

dune file working:

(executable (name main) (libraries threads netsys))

To compile with ocamlbuild:

touch _tags
ocamlbuild -use-ocamlfind -package netsys main.native

Netsys META file:

description = "Ocamlnet - OS-specific functions"
requires = "bytes,unix,bigarray"
version = "4.1.6"
archive(byte) = "netsys_oothr.cma netsys.cma"
archive(native) = "netsys_oothr.cmxa netsys.cmxa"
archive(native,gprof) = "netsys_oothr.p.cmxa netsys.p.cmxa netsys_c_gprof.o netsys_gprof_init.p.cmx"
archive(byte,mt) = "netsys_oothr_mt.cma netsys_oothr_mt_init.cmo netsys.cma"
archive(native,mt) = "netsys_oothr_mt.cmxa netsys_oothr_mt_init.cmx netsys.cmxa"
archive(native,gprof,mt) = "netsys_oothr_mt.p.cmxa netsys_oothr_mt_init.p.cmx netsys.p.cmxa"
archive(byte,toploop) = "netsys_oothr.cma netsys.cma"
archive(byte,mt,toploop) = "netsys_oothr_mt.cma netsys_oothr_mt_init.cmo netsys.cma"

plugin(byte) = "netsys_oothr.cma netsys.cma"
plugin(byte,mt) = "netsys_oothr_mt.cma netsys_oothr_mt_init.cmo netsys.cma"
plugin(native) = "netsys_oothr.cmxs netsys.cmxs"
plugin(native,mt) = "netsys_oothr_mt.cmxs netsys_oothr_mt_init.cmxs netsys.cmxs"
plugin(native,gprof,mt) = "netsys_oothr_mt.p.cmxs netsys_oothr_mt_init.p.cmxs netsys.p.cmxs"

package "outofheap" (
        version = "4.1.6"
        description = "Ocamlnet - override caml_modify and caml_initialize"
        requires = ""
	exists_if = "netsys_c_outofheap.o"
        archive(byte) = "netsys_c_outofheap.o"
        archive(native) = "netsys_c_outofheap.o"
        linkopts(byte) = "-custom"
)

[ghost]

I'm not sure why it works with ocamlfind, maybe ocamlfind does some magic to automatically add threads in some cases? In any case, this looks like an issue with the meta file of netsys

[Khady]

Might be related to #96?

[ghost]

Not really, the META file of netsys still looks wrong to me and it should declare a dependency on threads when mt is set. There is not much we can do in dune.

[ghost]

Ah, looking at #96 I see that ocamlfind indeed has some magic. I'm not really keen on adding this to dune though. Could you try sending a patch to netsys instead?

[Khady]

It is already reported at https://gitlab.camlcity.org/gerd/lib-ocamlnet3/issues/14

Closing this issue then. Thanks!