al_destroy_display - Allegro 5 API

       Destroy a display.

       If  the  target  bitmap  of  the  calling  thread  is  tied  to  the  display,  then it implies a call to
       “al_set_target_bitmap(NULL);” before the display is destroyed.

       That special case notwithstanding, you should make sure no threads are currently targeting a bitmap which
       is tied to the display before you destroy it.

       al_destroy_display - Allegro 5 API

al_set_target_bitmap(3alleg5)

Allegro reference manual                                                             al_destroy_display(3alleg5)

              #include <allegro5/allegro.h>

              void al_destroy_display(ALLEGRO_DISPLAY *display)