These functions are declared in the main Allegro header file:

     #include <allegro5/allegro.h>

# ALLEGRO_PI

    #define ALLEGRO_PI        3.14159265358979323846

Source Code

C99 compilers have no predefined value like M_PI for the constant π, but you can use this one instead.

Examples:

- ex_convert.c
- ex_opengl.c
- ex_blend_bench.c

# al_run_main

    int al_run_main(int argc, char **argv, int (*user_main)(int, char **))

Source Code

This function is useful in cases where you don’t have a main() function but want to run Allegro (mostly useful in a wrapper library). Under Windows and Linux this is no problem because you simply can call al_install_system. But some other system (like OSX) don’t allow calling al_install_system in the main thread. al_run_main will know what to do in that case.

The passed argc and argv will simply be passed on to user_main and the return value of user_main will be returned.

Allegro version 5.2.11 - Last updated: 2026-02-09 02:00:41 UTC