Hi everybody,

I'm trying to call a OCaml function from C code. This is the OCaml file:

open Printf

let hello () =
    Printf.fprintf stdout "%s" "test"
   
let () =
    let oc = open_out "/tmp/testfile" in
    Printf.fprintf oc "test";
    close_out oc;
   
    Printf.fprintf stdout "Caml main function\n";
   
    Callback.register "Hello callback" hello;
   
    Printf.fprintf stdout "%s" "Finished with OCaml initialization"
;;

and this is the C file:

#include <stdio.h>
#include <caml/memory.h>
#include <caml/mlvalues.h>
#include <caml/callback.h>

void helloWrapper()
{
    static value *closure_f = NULL;

    if(closure_f == NULL)
    {
        printf("1\n");
        closure_f = caml_named_value("Hello callback");
        printf("2\n");
        printf("Closure pointer: %p\n", closure_f);
    }
    printf("3\n");
    caml_callback(*closure_f, Val_unit);
}

int main(int argc, char **argv)
{
    caml_main(argv);

    printf("calling wrapper\n");
    helloWrapper();

    printf("Done.");
    return 0;
}

Everything seems to work: The file "/tmp/testfile" is created correctly (so the OCaml function did get called), and the C program ends with "Done.", but nothing is printed from the OCaml fprintf functions.

I am linking the executable with

$(OCAMLOPT) -output-obj test.ml -o test_obj.o
$(CC) -c linkwiththis.c -o linkwiththis.o -I"`$(OCAMLC) -where`"
$(CC) linkwiththis.o test_obj.o $(NATIVECCLIBS) -lasmrun -o camltestprogram -L"`$(OCAMLC) -where`"

What am I doing wrong - how can I make OCaml print to stdout correctly?

Best regards,
    Andreas