A .cma or .cmxa archive does not pack its sub-modules under a common
module name: the module name Puz_plugin that you use does not refer to
anything. Accessing any of the constituent modules directly (eg.
Puz_match.foo) should work -- although it may not go through the .cmxa
but directly refer to the compilation unit.

Note that if "_plugin" is intended to refer to dynamic linking, you
may want to use a .mldylib file instead of .mllib, to be used to
generate a .cmxs file: .cmxa is not suitable for dynamic linking
(while, at the bytecode level, .cma work for both static and dynamic
linking).

On Tue, Sep 22, 2015 at 8:23 AM, Martin DeMello <martindemello@gmail.com> wrote:
> If I have my project set up like this:
>
> .
> ├── file.ml
> ├── plugins
> │   └── puz
> │       ├── puz_bin.ml
> │       ├── puz_match.ml
> │       ├── puz.ml
> │       ├── puz_plugin.mllib
> │       ├── puz_types.ml
> │       └── puz_utils.ml
> └── _tags
>
> $ cat plugins/puz/puz_plugin.mllib
> Puz Puz_bin Puz_match
>
> This works:
>
> $ ocamlbuild -use-ocamlfind plugins/puz/puz_plugin.cmxa
> Finished, 22 targets (3 cached) in 00:00:03.
>
> My _tags file:
> ------------------------------------------------
> $ cat _tags
> true: thread,debug
> true: package(core_kernel)
>
> "plugins/puz": include
>
> <gui.*>: package(labltk)
> <**/puz.*>: package(unix), package(str), package(core_kernel),
> package(bitstring), package(mikmatch_pcre)
> <**/*_bin.*>: package(bitstring.syntax), syntax(bitstring)
> <**/*_match.*>: package(mikmatch_pcre), syntax(camlp4o)
> ------------------------------------------------
>
> But I can't figure out how to use this library in my main program. This is a
> minimal example of what I'm trying to do, not working of course:
>
> $ cat file.ml
> open Core_kernel.Std
>
> let read fname =
>   let data = In_channel.read_all fname in
>   Puz_plugin.read data
>
> $ ocamlbuild -use-ocamlfind file.native
> + ocamlfind ocamlc -c -g -thread -package core_kernel -I plugins/puz -o
> file.cmo file.ml
> File "file.ml", line 5, characters 2-17:
> Error: Unbound module Puz_plugin
>
> martin