al_get_opengl_program_object - Allegro 5 API

       Returns  the  OpenGL  program object associated with this shader, if the platform is ALLEGRO_SHADER_GLSL.
       Otherwise, returns 0.

Allegro reference manual                                                   al_get_opengl_program_object(3alleg5)

       al_get_opengl_program_object - Allegro 5 API

              #include <allegro5/allegro_opengl.h>

              GLuint al_get_opengl_program_object(ALLEGRO_SHADER *shader)