Question

I’m working on a lib that uses Glib internally to connect to other modules.

This lib has a initialize method that sets up the dbus connection and a terminate method that finalizes all the internal resources (including the dbus connection).
At least it should do this.

However, I can’t make dbus calls again after the terminate method gets called (of course I called the initialize method again before calling the dbus methods again).

I’m using C++ mainly (a few used libs are in C).

Here is my internal dbus initializer:

#ifdef __cplusplus
extern "C" {
#endif

#include <dbus/dbus-glib.h>
#include <stdio.h>

#define _DBUS_SERVICE       "Removed due to restrictions"
#define _DBUS_PATH      "/"
#define _DBUS_INTERFACE "Removed due to restrictions"

static DBusGConnection * my_dbus_conn = NULL;
static DBusGProxy * my_proxy = NULL;

gboolean dbus_init() {
    GError *error = NULL;
    g_type_init();
    my_dbus_conn = dbus_g_bus_get(DBUS_BUS_SESSION, &error);
    if (my_dbus_conn == NULL) {
        g_printerr("DBUS Connection Error (%s)\n", error->message);
        g_error_free(error);
        return false;
    }
    my_proxy = dbus_g_proxy_new_for_name(my_dbus_conn, _DBUS_SERVICE, _DBUS_PATH, _DBUS_INTERFACE);
    if (my_proxy == NULL) {
        g_printerr("ERROR: DBUS Proxy creation Error (%s)\n", error->message);
        g_error_free(error);
        return false;
    }
    return true;
}

DBusGProxy * dbus_get_proxy() {
    if (my_proxy == NULL) {
        dbus_init();
    }
    return my_proxy;
}

void dbus_term() {
    g_object_unref(G_OBJECT (my_proxy));
    dbus_g_connection_unref(my_dbus_conn);
    my_dbus_conn = NULL;
}

#ifdef __cplusplus
}
#endif

Here is my calling code:

MY_G_DEBUG("Manager", "Creating Server IPC stub...");
this->m_pDbusServer = get_proxy();

if (this->m_pDbusServer == NULL) {
    return;
}

MY_G_DEBUG("Manager", "CheckPoint 1!");
gboolean success;
GError *gerror = NULL;
char **l_pHelloWorldReply;

success = dbus_server_helloworld(this->m_pDbusServer, "Hello World from Manager", &l_pHelloWorldReply, &gerror);

MY_G_DEBUG("Manager", "CheckPoint 2!");

if (success == FALSE) {
    MY_G_DEBUG("Manager", "CheckPoint 3!");
    if (gerror == NULL) {
        MY_G_DEBUG("Manager", "CRITICAL: Hello World call Failed (error not set)");
    } else {
        MY_G_DEBUG("Manager", "CRITICAL: Hello World call Failed (%s)", gerror->message);
        g_error_free(gerror);
        gerror = NULL;
    }
    return;
} else {
    MY_G_DEBUG("Manager", "CheckPoint 4!");
    for (guint ii = 0; l_pHelloWorldReply[ii] != NULL; ii++) {
        MY_G_DEBUG("Manager", "Hello World response %d: %s", ii, l_pHelloWorldReply[ii]);
    }
}

MY_G_DEBUG("Manager", "CheckPoint 5!");

Here is the logging output:

(process:24498): Manager-DEBUG: Checkpoint: 1!
(process:24498): Manager-DEBUG: Checkpoint: 2!
(process:24498): Manager-DEBUG: Checkpoint: 3!
(process:24498): Manager-DEBUG: CRITICAL: Hello World call Failed (error not set)

I got an error message everytime I call the dbus_term function, however I couldn’t manage to fix it.

(process:24498): GLib-GObject-WARNING **: invalid uninstantiatable type `<invalid>' in cast to `GObject'
(process:24498): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed

The first time I try to call methods, everything works well…
I strongly believe that’s caused by the dbus_term issue.

Does anyone have any idea why that is happening?

Thanks very much.

Answer 1

Don’t use dbus-glib in new code, use GDBus instead.

GDBus is the new dbus api in glib 2.26. Its advantages over dbus-glib include the use of the GIO async patterns (GAsync*, GCancellable), the use of GVariant for variant types and better threading support.

See
http://library.gnome.org/devel/gio/2.28/ch29.html for migrating to GDBus.