al_ustr_rfind_str - Allegro 5 API

       Find the last occurrence of string needle in haystack before byte offset end_pos (exclusive).  Return the
       byte offset of the occurrence if it is found, otherwise return -1.

       al_ustr_rfind_str - Allegro 5 API

al_ustr_rfind_cstr(3alleg5), al_ustr_find_str(3alleg5)

Allegro reference manual                                                              al_ustr_rfind_str(3alleg5)

              #include <allegro5/allegro.h>

              int al_ustr_rfind_str(const ALLEGRO_USTR *haystack, int end_pos,
                 const ALLEGRO_USTR *needle)