Function drmgr_unregister_thread_init_event_user_data 

pub unsafe extern "C" fn drmgr_unregister_thread_init_event_user_data(
    func: Option<unsafe extern "C" fn(drcontext: *mut c_void, user_data: *mut c_void)>,
) -> bool_

Unregister a callback function for the thread initialization event which also has user data passed to the callback. \return true if unregistration is successful and false if it is not (e.g., \p func was not registered).

See also drmgr_unregister_thread_init_event().