gobject:type-default-interface-unref (iface)

iface -- a pointer to the default vtable instance for an interface, as returned by the g:type-default-interface-ref function

Decrements the reference count for the type corresponding to the interface default vtable of iface. If the type is dynamic, then when no one is using the interface and all references have been released, the finalize function for the default vtable of the interface will be called.