al_get_joystick_button_name - Allegro 5 API

       Return  the name of the given button.  If the button doesn’t exist, NULL is returned.  Indices begin from
       0.

       al_get_joystick_button_name - Allegro 5 API

al_get_joystick_stick_name(3alleg5),                                  al_get_joystick_axis_name(3alleg5),
       al_get_joystick_num_buttons(3alleg5)

Allegro reference manual                                                    al_get_joystick_button_name(3alleg5)

              #include <allegro5/allegro.h>

              const char *al_get_joystick_button_name(ALLEGRO_JOYSTICK *joy, int button)