Actually, I think it's that ocamlbuild should be told to link
libdai_stubs.a, and not try and build it. But also, I wanted to reference
an existing work that links with C libraries, and I found ocamlbuild's
example, with-c. I tried to build it, and I found that it isn't built by
the harness default. Also, if you just try and build within just that raw
directory in isolation, that it fails with a similar error I had been
getting earlier. I looked around and found these:

https://stackoverflow.com/questions/19644451/how-to-make-ocamlbuild-compile-and-link-a-c-file-into-an-ocaml-project
https://l-lang.blogspot.com/2012/08/incorporating-c-code-in-ocaml-project.html
https://ocaml.org/learn/tutorials/ocamlbuild/Using_an_external_library.html

And I'm trying to follow, but they each give unique directions, each seem
to not work for me.

On Sat, Aug 26, 2017 at 9:12 PM, Kenneth Adam Miller <
kennethadammiller@gmail.com> wrote:

> Hello,
>
>
> I'm building a pair of companion oasis build spec and opam package setup
> for a C library. libdai I figured out how to get swig and oasis to build
> most things I need, but I'm having trouble getting oasis to not generate
> _stubs targets that aren't found. There is a static C/++ libdai.a file that
> is the product of the project I'm trying to wrap. I can't convince oasis to
> use that instead. Here's my _oasis target:
>
>
> Library "dai"
>   Path:                 ./
>   Install:              false
>   Modules:              Swig, Dai
>   CompiledObject:       best
>   CSources:             dai_wrap.cxx.c
>   CCOpt:                -g -xc++ "-I../../include"
>
>
> With a fresh clone of libdai, I get dai_wrap.cxx.c by doing the following
> in ./swig after building libdai:
>
> $(SWIG) -ocaml -c++  dai.i
> mv dai_wrap.cxx dai_wrap.cxx.c
> sed -i -e 's/caml_array_length/caml_array_len/g' dai_wrap.cxx.c
>
> I got my swig and dai ml files by doing the following:
>
> swig2.0 -ocaml -co dai.ml
> swig2.0 -ocaml -co swig.ml
> swig2.0 -ocaml -co swig.mli
>
> I build by doing the following:
>
> ocaml setup.ml -configure
> ocaml setup.ml -build
>
>
> I get the following error:
>
>
> Solver failed:
>   Ocamlbuild knows of no rules that apply to a target named
> ./libdai_stubs.a. This can happen if you ask Ocamlbuild to build a target
> with the wrong extension (e.g. .opt instead of .native) or if the source
> files live in directories that have not been specified as include
> directories.
> Compilation unsuccessful after building 8 targets (8 cached) in 00:00:00.
> E: Failure("Command ''/usr/bin/ocamlbuild' ./libdai_stubs.a
> ./dlldai_stubs.so ./dai.cma ./dai.cmxa ./dai.a ./dai.cmxs -j 5 -tag debug'
> terminated with error code 6")
>
> I want to make sure that the actual target shared library that was
> produced by the libdai build file itself is linked against. But oasis is
> assuming I have a _stubs target. I read in the documentation here that: "The
> usual idiom is to append _stubs to the name."
> https://ocaml.org/learn/tutorials/setting_up_with_
> oasis.html#Interfacing-with-C-code
>
> And I think that that is the source of the error, but it isn't well
> explained. The ultimate things I originally wanted was to be able to use
> libdai with both the utop or the bytecode interpreter and with fully
> compiled targets. I was going to make libdai a library and then publicize
> it.
>
> If anybody needs to replicate my issue, I have a docker container with
> this already.
>