Tutorial example for nat dynlink

Tutorial example for nat dynlink

[Yves Bertot]

Hello,

I have been trying to build a small example "hello world" program using 
native dynlink, but
I don't manage to make it work.  Could please send me some advice?


Here are my programs:

-------- toto.mli ----
val ff : (unit -> unit) ref;;
-------- toto.ml -----
Dynlink.init();;

let ff = ref (fun () -> ());;

try Dynlink.loadfile "bidon.cmxs" with Dynlink.Error(e) ->
  print_string (Dynlink.error_message e ^ "\n");;

!ff();;
------ bidon.ml -----
let hello () = print_string "hello world!\n";;

Toto.ff := hello;;
------ end of files ------

ocamlopt -v returns

The Objective Caml native-code compiler, version 3.11.0+beta1
Standard library directory:  .../lib/ocaml

And I compile my files in the following manner.

ocamlopt toto.mli
ocamlopt -shared -o bidon.cmxs bidon.ml
ocamlopt -o toto dynlink.cmxa toto.ml

My test runs as follows, with a behavior I did not expect:

./toto
no implementation available for Toto

Can you tell me what is missing in my experiment, or point me to an 
example that would be about the same size?

Yves

Re: [Caml-list] Tutorial example for nat dynlink

[Xavier Leroy]

Hello Yves,

> I have been trying to build a small example "hello world" program
> using native dynlink, but I don't manage to make it work.  Could
> please send me some advice?

The issue here is that when Dynlink.loadfile is called, module Toto is
not yet completely evaluated, therefore it is not yet visible to
dynamically-loaded code.  The solution is just to split your main
program in two modules: Toto containing what your plugin needs to see,
and Totomain performing the dynlink.  Then, it'll work just fine.

Cheers,

- Xavier