GDBusServer: Make ::new-connection return whether the connection was claimed

Otherwise things probably won't work in a garbage-collected world
(consider the trivial GC that never collects garbage).

This commit breaks GDBusServer ABI. No known released software is
using this code.

Signed-off-by: David Zeuthen <davidz@redhat.com>

gio/gdbusserver.c

@@ -122,7 +122,7 @@ struct _GDBusServerClass
 
   /*< public >*/
   /* Signals */
-  void (*new_connection) (GDBusServer      *server,
+  gboolean (*new_connection) (GDBusServer      *server,
                               GDBusConnection  *connection);
 };
 
@@ -391,10 +391,12 @@ g_dbus_server_class_init (GDBusServerClass *klass)
    * g_dbus_connection_get_peer_credentials() to figure out what
    * identity (if any), was authenticated.
    *
-   * If you want to accept the connection, simply ref the @connection
+   * If you want to accept the connection, take a reference to the
-   * object. Then call g_dbus_connection_close() and unref it when you
+   * @connection object and return %TRUE. When you are done with the
-   * are done with it. A typical thing to do when accepting a
+   * connection call g_dbus_connection_close() and give up your
-   * connection is to listen to the #GDBusConnection::closed signal.
+   * reference. Note that the other peer may disconnect at any time -
+   * a typical thing to do when accepting a connection is to listen to
+   * the #GDBusConnection::closed signal.
    *
    * If #GDBusServer:flags contains %G_DBUS_SERVER_FLAGS_RUN_IN_THREAD
    * then the signal is emitted in a new thread dedicated to the
@@ -407,16 +409,19 @@ g_dbus_server_class_init (GDBusServerClass *klass)
    * that it's suitable to call g_dbus_connection_register_object() or
    * similar from the signal handler.
    *
+   * Returns: %TRUE to claim @connection, %FALSE to let other handlers
+   * run.
+   *
    * Since: 2.26
    */
   _signals[NEW_CONNECTION_SIGNAL] = g_signal_new ("new-connection",
                                                   G_TYPE_DBUS_SERVER,
                                                   G_SIGNAL_RUN_LAST,
                                                   G_STRUCT_OFFSET (GDBusServerClass, new_connection),
-                                                  NULL,
+                                                  g_signal_accumulator_true_handled,
-                                                  NULL,
+                                                  NULL, /* accu_data */
-                                                  g_cclosure_marshal_VOID__OBJECT,
+                                                  _gio_marshal_BOOLEAN__OBJECT,
-                                                  G_TYPE_NONE,
+                                                  G_TYPE_BOOLEAN,
                                                   1,
                                                   G_TYPE_DBUS_CONNECTION);
 }
@@ -922,11 +927,16 @@ static gboolean
 emit_new_connection_in_idle (gpointer user_data)
 {
   EmitIdleData *data = user_data;
+  gboolean claimed;
 
+  claimed = FALSE;
   g_signal_emit (data->server,
                  _signals[NEW_CONNECTION_SIGNAL],
                  0,
-                 data->connection);
+                 data->connection,
+                 &claimed);
+
+  if (claimed)
     g_dbus_connection_start_message_processing (data->connection);
   g_object_unref (data->connection);
 

gio/gio-marshal.list

@@ -21,3 +21,4 @@ VOID:STRING,STRING,VARIANT
 VOID:STRING
 VOID:STRING,STRING
 VOID:STRING,BOOLEAN
+BOOL:OBJECT

gio/tests/gdbus-example-peer.c

@@ -121,7 +121,7 @@ static const GDBusInterfaceVTable interface_vtable =
 
 /* ---------------------------------------------------------------------------------------------------- */
 
-static void
+static gboolean
 on_new_connection (GDBusServer *server,
                    GDBusConnection *connection,
                    gpointer user_data)
@@ -152,6 +152,8 @@ on_new_connection (GDBusServer *server,
                                                        NULL,  /* user_data_free_func */
                                                        NULL); /* GError** */
   g_assert (registration_id > 0);
+
+  return TRUE;
 }
 
 /* ---------------------------------------------------------------------------------------------------- */

gio/tests/gdbus-peer.c

@@ -283,7 +283,7 @@ on_authorize_authenticated_peer (GDBusAuthObserver *observer,
 }
 
 /* Runs in thread we created GDBusServer in (since we didn't pass G_DBUS_SERVER_FLAGS_RUN_IN_THREAD) */
-static void
+static gboolean
 on_new_connection (GDBusServer *server,
                    GDBusConnection *connection,
                    gpointer user_data)
@@ -311,6 +311,8 @@ on_new_connection (GDBusServer *server,
   g_assert (reg_id > 0);
 
   g_main_loop_quit (loop);
+
+  return TRUE;
 }
 
 static gpointer
@@ -943,7 +945,7 @@ static const GDBusInterfaceVTable dmp_interface_vtable =
 
 
 /* Runs in thread we created GDBusServer in (since we didn't pass G_DBUS_SERVER_FLAGS_RUN_IN_THREAD) */
-static void
+static gboolean
 dmp_on_new_connection (GDBusServer     *server,
                        GDBusConnection *connection,
                        gpointer         user_data)
@@ -984,6 +986,8 @@ dmp_on_new_connection (GDBusServer     *server,
                                      NULL,
                                      &error);
   g_dbus_node_info_unref (node);
+
+  return TRUE;
 }
 
 static gpointer
@@ -1101,7 +1105,7 @@ nonce_tcp_on_authorize_authenticated_peer (GDBusAuthObserver *observer,
 }
 
 /* Runs in thread we created GDBusServer in (since we didn't pass G_DBUS_SERVER_FLAGS_RUN_IN_THREAD) */
-static void
+static gboolean
 nonce_tcp_on_new_connection (GDBusServer *server,
                              GDBusConnection *connection,
                              gpointer user_data)
@@ -1111,6 +1115,8 @@ nonce_tcp_on_new_connection (GDBusServer *server,
   g_ptr_array_add (data->current_connections, g_object_ref (connection));
 
   g_main_loop_quit (loop);
+
+  return TRUE;
 }
 
 static gpointer