Function dr_unregister_pre_detach_event 

pub unsafe extern "C" fn dr_unregister_pre_detach_event(
    func: Option<unsafe extern "C" fn()>,
) -> bool_

Unregister a callback function for the post-attach event (see dr_register_pre_detach_event()). \return true if unregistration is successful and false if it is not (e.g., \p func was not registered).