al_get_errno - Allegro 5 API

       Some  Allegro  functions will set an error number as well as returning an error code.  Call this function
       to retrieve the last error number set for the calling thread.

Allegro reference manual                                                                   al_get_errno(3alleg5)

       al_get_errno - Allegro 5 API

              int al_get_errno(void)
              GETTER(allegro_errno, 0)