al_create_thread - Allegro 5 API

       Spawn  a  new thread which begins executing proc.  The new thread is passed its own thread handle and the
       value arg.

       Returns a pointer to the thread on success.  Otherwise, returns NULL if there was an error.

       al_create_thread - Allegro 5 API

al_start_thread(3alleg5), al_join_thread(3alleg5).

Allegro reference manual                                                               al_create_thread(3alleg5)

              #include <allegro5/allegro.h>

              ALLEGRO_THREAD *al_create_thread(
                 void *(*proc)(ALLEGRO_THREAD *thread, void *arg), void *arg)