the GClosure to which the marshaller belongs
a GValue, which can store the returned string
a GValue array holding instance, arg1 and arg2
the invocation hint given as the last argument to g_closure_invoke()
additional data specified when registering the marshaller
A marshaller for a GCClosure with a callback of type gchar* (*callback) (gpointer instance, GObject *arg1, gpointer arg2, gpointer user_data).