[Chicken-users] A more concrete FFI question.

[Robin Lee Powell]

The following C code (trimmed) works fine:

    xmmsc_connection_t *connection;
    xmmsc_result_t *result;

    unsigned int id;

    result = xmmsc_playback_current_id (connection);

    xmmsc_result_wait (result);

    if (!xmmsc_result_get_uint (result, &id)) {
            fprintf (stderr, "xmmsc_playback_current_id didn't"
                    "return uint as expected\n");
    }

    printf ("Currently playing id is %d\n", id);

The following Chicken does not:

(let-location ([ret unsigned-int 275])
              (let* (
                     [res ($ c-pointer xmmsc_broadcast_playback_current_id 
(c-pointer conn))]
                     [null ($ void xmmsc_result_wait (pointer res))]
                     [boring-ret ($ int xmmsc_result_get_uint (pointer res) 
(location ret))])
                (display (conc "Currently playing test : " boring-ret ", " ret 
"\n"))))

The value in "ret" is always whatever value I initialize it to, like
it's not getting touched at all.

I don't, at all, understand the explanations for let-location,
location, or pointer (there being not much explanation for any of
them), so I'm sure I'm doing something wrong.

-Robin