Excerpts from christian.sternagel's message of Mon Jan 28 11:43:09 +0100 2008:
> On Mon, Jan 28, 2008 at 11:23:29AM +0100, Romain Bardou wrote:
> > I tried to reproduce a similar set of directories as yours. I couldn't 
> > get the "circular dependency" error, but I had to compile everything in 
> > one command line, otherwise the file a.cma (which is in the _build/A 
> Today I found out, that we indeed had a circular dependency:
> 
> An interface file B.mli used a type A.t, whereas the implementation
> file A.ml uses functions from B. When using ocamldep + a Makefile, no
> error occurred. But ocamlbuild refused to compile... I guess that is
> the right thing to do =)

Yes  ocamlbuild  treats  your  module (interface + implementation) as a whole.
Then  dependencies  are  computed for modules, so you are in a case that could
be  compiled  but  ocamlbuild  will  refuse  it. I'm a bit reluctant to change
this,  since  I  think  that  the  right  thing to do is to avoid this kind of
semi-cycles.

> > directory) was deleted before compiling b.cma. The command which I used 
> > and which worked is:
> > 
> > ocamlbuild -Is A,B a.cma b.cma
> > 
> > I don't really understand how the -lib option works though. Where and 
> > when does it look for the library x.cma with the "-lib x" option? How 
> > and what's the semantic of the "+" you can add at the beginning of a 
> > library name?...
> As far as I know, a `+' means that the following name should be searched
> relative to the standard library.

All  ocamlbuild  include  directories  must  be  implicit  and relative to the
current  dir.  So  dirs  like ../foo, /foo, +foo, ./foo are forbidden. You can
make  symbolic  link  to avoid the two first cases. If you really need to give
+foo  dir,  please  use non-interpreted compilation flags like -cflags for the
command line and tags like ["ocaml"; "compile"] for a tag based approach.

> Still my question remains, how one should configure a project
> that consists of several libraries and one binary, together
> with ocamlbuild. E.g.,
> 
> +- prof.dir/
> +-+- A/
> | +- a.mllib
> | +- a1.ml
> | +- ...
> | +- aN.ml
> |
> +-+- B/
> | +- b.mllib
> | +- b1.ml
> | +- ...
> | +- bN.ml
> |
> +-+- Main/
>   +- main.ml (depending on a.cma and b.cma)

The simplest thing to do is what you've tried (ocamlbuild -Is A,B Main/main.byte).

But here your mllib's are not used.

If you want to use them as libraries you need a small myocamlbuild.ml like:

$ cat myocamlbuild.ml
open Ocamlbuild_plugin;;
dispatch begin function
| After_rules ->
    ocaml_lib "A/a";
    ocaml_lib "B/b"
| _ -> ()
end

And to tag your files:

$ cat _tags
# tells that main use a and b libs
<Main/main.{byte,native}>: use_a, use_b
# this will avoid the need of command line options to ocamlbuild
"A" or "B": include

$ ocamlbuild Main/main.byte

Cheers,

PS: I've just updated the wiki [1]
[1]: http://brion.inria.fr/gallium/index.php/Using_internal_libraries

-- 
Nicolas Pouillard aka Ertai