Man pages matching name al_ffblk_get_size in section 3alleg4:

al_ffblk_get_size.3alleg4.en	debian 10 / allegro4-doc
al_ffblk_get_size.3alleg4.en	debian 11 / allegro4-doc
al_ffblk_get_size.3alleg4.en	debian 12 / allegro4-doc
al_ffblk_get_size.3alleg4.en	debian 13 / allegro4-doc