Answering to myself: the information needed by findlib to sort the cma
correctly is stored in the META file, using "require" directives. I

In fact I have a slightly more complicated structure:
- library A
- library B.B1 which depends on A
- library B.B2 which depends on B.B1 and A
- executable C which depends on all others

and I had forgotten the dependency between B.B1 and A. The error message
was mentionning B.B2 instead so I overlooked the real missing part. Sorry
for the noise!

Cheers,
  Philippe.

2012/12/19 Philippe Veber <philippe.veber@gmail.com>

> Dear all,
>
> I have 2 libraries, say A and B where B depends on A, and an executable C
> which uses both A and B. Each of these components is a separate (oasis)
> project. I have some test executables in B which work fine. However, when I
> compile C, the compiler complains that it has no implementation for a
> module defined in A and used in B. The compilation (linking) command of C
> contains "-package" options for A and B, it is of the form:
>
> ocamlfind ocamlopt ... -package B -package A ... C.cmo
>
> If I permute the two package options, like in
>
> ocamlfind ocamlopt ... -package A -package B ... C.cmo
>
> the compilation works fine. It is not really clear to me, but I thought
> the order of the -package options did not matter, because findlib would
> store the dependencies between packages and produce a compilation command
> where cma or cmxa are correctly sorted. Indeed, if I use the -verbose
> option, I can see that cma are wrongly sorted in the former case, while
> they are fine in the latter.
>
> Admitedly my description is rather abstract, but does anyone see what
> could I (or oasis) have forgotten, to tell ocamlfind that B.cma depends on
> A.cma?
>
> Cheers,
>   Philippe.
>
>