/* Ocaml code:
type foo = Bar of int;;
Callback.register "test-cb" (fun (x : int) -> Bar x);;
external do_test : int -> foo = "do_test";;

let _ = match do_test 4 with
    Bar x -> print_endline "success!";;
*/
// c code
#include<mlvalues.h>
#include<memory.h>
#include<assert.h>

CAMLprim value do_test(value foo) {
  CAMLparam1(foo);
  CAMLlocal1(ret);
  assert(Is_long(foo));
  value *cb = caml_named_value("test-cb");
  ret = caml_callback(*cb, foo);
  printf("%u\n", Tag_val(ret));
  CAMLreturn(ret);
}