al_get_thread_should_stop - Allegro 5 API

       Check  if  another  thread  is waiting for thread to stop.  Threads which run in a loop should check this
       periodically and act on it when convenient.

       Returns true if another thread has called al_join_thread(3alleg5)  or  al_set_thread_should_stop(3alleg5)
       on this thread.

       al_get_thread_should_stop - Allegro 5 API

al_join_thread(3alleg5), al_set_thread_should_stop(3alleg5).

              Note: We don’t support forceful killing of threads.

Allegro reference manual                                                      al_get_thread_should_stop(3alleg5)

              #include <allegro5/allegro.h>

              bool al_get_thread_should_stop(ALLEGRO_THREAD *thread)