diff -urN ./files/camlpdfc.mlcdll ./files-modified/camlpdfc.mlcdll
--- ./files/camlpdfc.mlcdll	1970-01-01 01:00:00.000000000 +0100
+++ ./files-modified/camlpdfc.mlcdll	2009-01-20 22:16:52.000000000 +0100
@@ -0,0 +1,2 @@
+Cpdflibc
+cpdflibwrapper.o
diff -urN ./files/cpdflibc.ml ./files-modified/cpdflibc.ml
--- ./files/cpdflibc.ml	2009-01-20 18:00:51.000000000 +0100
+++ ./files-modified/cpdflibc.ml	2009-01-20 22:23:27.000000000 +0100
@@ -1,2 +1,4 @@
 (* cpdflibc.ml *)
 let twice x = x * 2
+
+let _ = Callback.register "twice" twice
diff -urN ./files/cpdflibwrapper.c ./files-modified/cpdflibwrapper.c
--- ./files/cpdflibwrapper.c	2009-01-20 18:00:51.000000000 +0100
+++ ./files-modified/cpdflibwrapper.c	2009-01-20 22:18:58.000000000 +0100
@@ -2,10 +2,33 @@
 #include <stdio.h>
 #include <caml/memory.h>
 #include <caml/callback.h>
+#include <assert.h>
 
+#define CAMLPDFLIB_CAMLCBK_INIT( callback, cbk_name) \
+        static value *callback = NULL; \
+        if (callback == NULL) callback = \
+              caml_named_value(cbk_name);\
+          assert(callback);
+
+static int cpdflibc_init_done = 0;
+
+void
+init_cpdflib ()
+{
+  char *vide[1];
+  vide[0] = NULL;
+  if (!cpdflibc_init_done)
+    {
+      caml_startup (vide);
+      cpdflibc_init_done = 1;
+    }
+}
+ 
 int twice_c (int i)
 {
-  CAMLlocal1 (result);
-  result = caml_callback(*caml_named_value("twice"), Val_int(i));
-  return(0);
+  CAMLparam0();
+  CAMLlocal1(res);
+  CAMLPDFLIB_CAMLCBK_INIT(cbk, "twice");
+  res = caml_callback(*cbk, Val_int(i));
+  CAMLreturnT(int, Int_val(res));
 }
diff -urN ./files/cpdflibwrapper.h ./files-modified/cpdflibwrapper.h
--- ./files/cpdflibwrapper.h	2009-01-20 18:00:51.000000000 +0100
+++ ./files-modified/cpdflibwrapper.h	2009-01-20 22:22:45.000000000 +0100
@@ -1,3 +1,4 @@
 /* cpdflibwrapper.h */
-int twice (int);
+void init_cpdflib();
+int twice_c (int);
 
diff -urN ./files/myocamlbuild.ml ./files-modified/myocamlbuild.ml
--- ./files/myocamlbuild.ml	1970-01-01 01:00:00.000000000 +0100
+++ ./files-modified/myocamlbuild.ml	2009-01-20 22:19:59.000000000 +0100
@@ -0,0 +1,103 @@
+open Ocamlbuild_plugin
+open Command
+open Outcome
+
+let (ext_o, ext_so, syst) =
+  let my_ocamlc_config =
+    let rec sc s h = 
+      Scanf.sscanf s "%s@: %s@\n%n" 
+        begin fun k v n -> 
+          let h' = (k, v) :: h in
+          let len = String.length s in  
+            if 
+              len - n <= 0 
+            then 
+              h'
+            else 
+              sc (String.sub s n (len - n)) h'
+        end in
+      sc (Ocamlbuild_pack.My_unix.run_and_read "ocamlc -config") [] in
+    match 
+      List.map 
+        (fun x -> List.assoc x my_ocamlc_config)
+        ["ext_obj"; "ext_dll"; "system";] 
+    with
+        [ext_o; ext_so; syst] -> ext_o, ext_so, syst
+      | _ -> assert false
+
+exception Found of string
+
+let pwd () =
+  let env = Array.to_list (Unix.environment ()) in
+  let rec search = function
+      [] -> ""
+    | h :: tl ->
+        try 
+          Scanf.sscanf h "PWD=%s" (fun x -> x) 
+        with 
+            _ -> search tl in
+    search env
+    
+let uncap_module_path p =
+  (Pathname.dirname p) / (String.uncapitalize (Pathname.basename p))
+
+let _ = dispatch begin function
+
+  | After_rules ->
+	  	  
+	  flag ["link";"mlcdll"] (S[A"-output-obj"]);
+	  	  
+      rule "Mixed C-Ocaml native DLL: mlcdll & o* & cmx* -> native DLL (.dll | .so)"
+        ~dep:"%.mlcdll"
+        ~prod:("%.native" ^ ext_so)
+        begin
+          fun env build ->
+            let output = env ("%.native" ^ ext_so)
+            and input = env "%.mlcdll" in
+            let dir = Pathname.dirname input in
+			  
+            (* TODO: use functions of Pathname module? *)
+            let ext_o_files, moduls_files = 
+              string_list_of_file input |>
+                  List.partition (fun fic -> Filename.check_suffix fic ".o") in
+            let objs = ext_o_files |>
+                List.map Filename.chop_extension |>
+                    List.map (fun fic -> fic ^ ext_o) in
+            let cmxs = moduls_files |>
+                List.map (fun modul ->
+                            (uncap_module_path modul) -.- "cmx") in
+            let deps = cmxs @ objs in
+			  
+              List.iter ignore_good 
+                (build (List.map (fun x -> [dir/x]) deps));
+			  
+              Cmd (S [!Options.ocamlopt;
+                      A"-o"; Px output;
+                      T (tags_of_pathname output++"ocaml"++"native"++"mlcdll"++"link");
+                      atomize_paths deps
+                     ])
+        end;
+	  
+      (* Allows to have .h copied in the _build directory *)
+      dep ["file:cpdflibwrapper.c"] ["cpdflibwrapper.h"];
+	  dep ["file:test.c"]["cpdflibwrapper.h"];
+	  
+      rule "Compile test.native"
+        ~deps:["test.o"; "camlpdfc.native.so"]
+        ~prod:"test.native"
+        begin fun _ _ ->
+          let target = "test.native" in
+          let spc = "-Wl,-rpath=" ^ ((pwd ()) / (!Options.build_dir))  in
+            Cmd(
+              S[
+                A"gcc";
+                A"-o";A target;
+                A"test.o";
+                A"-l:camlpdfc.native.so";
+                A"-L."; A spc;
+              ])
+        end;
+
+
+  | _ -> ()
+end
diff -urN ./files/test.c ./files-modified/test.c
--- ./files/test.c	2009-01-20 18:00:51.000000000 +0100
+++ ./files-modified/test.c	2009-01-20 22:20:29.000000000 +0100
@@ -4,6 +4,7 @@
 
 int main ()
 {
+  init_cpdflib();
   printf("Twice two is %i\n", twice_c(2));
   return(0);
 }