Foreign can't find symbols statically linked in

[pqwy]

I have two files:

foo.c:

int foo () { return 42; }

bar.ml:

open Ctypes
let foo = Foreign.foreign "foo" (void @-> returning int)
let _ = print_int (foo ())

Compiling foo as shared works:

$ clang -shared -fPIC foo.c -o libfoo.so
$ ocamlfind ocamlopt -linkpkg -package ctypes,ctypes.foreign bar.ml -o bar
$ LD_PRELOAD=./libfoo.so ./bar
42
$

But not linking it in:

$ clang -c -fPIC foo.c
$ ocamlfind ocamlopt -linkpkg -package ctypes,ctypes.foreign foo.o bar.ml -o bar
$ ./bar
Fatal error: exception Dl.DL_error("./bar: undefined symbol: foo")

Binding it via:

external foo : unit -> int = "foo"

... picks it up, however.

Can I overcome this somehow?

[dsheets]

I have been using, e.g.:

int unix_unistd_unlink(const char *pathname) {
  int retval;
  caml_release_runtime_system();
  retval = unlink(pathname);
  caml_acquire_runtime_system();
  return retval;
}

value unix_unistd_unlink_ptr(value _) {
  UNUSED(_);
  return caml_copy_int64((intptr_t)(void *)unix_unistd_unlink);
}

let local ?check_errno addr typ =
  coerce (ptr void) (funptr ?check_errno typ) (ptr_of_raw_address addr)

external unix_unistd_unlink_ptr : unit -> int64 = "unix_unistd_unlink_ptr"

let unlink =
  let c = local ~check_errno:true (unix_unistd_unlink_ptr ())
    PosixTypes.(string @-> returning int)
  in
  fun pathname ->
    try ignore (c pathname)
    with Unix.Unix_error(e,_,_) -> raise (Unix.Unix_error (e,"unlink",pathname))

[yallop]

Adding -E to the linker command line does the trick for me:

$ clang -c -fPIC foo.c
$ ocamlfind ocamlopt -linkpkg -package ctypes,ctypes.foreign -cclib -Wl,-E foo.o bar.ml -o bar
$ ./bar
42

[dsheets]

Sweet! 👍

[pqwy]

Yes, that's the one. Thanks!