al_register_trace_handler - Allegro 5 API

       Register  a  callback  which  is  called whenever Allegro writes something to its log files.  The default
       logging to allegro.log is disabled while this callback is active.  Pass NULL to  revert  to  the  default
       logging.

       This function may be called prior to al_install_system.

       See  the  example  allegro5.cfg  for  documentation  on how to configure the used debug channels, logging
       levels and trace format.

       al_register_trace_handler - Allegro 5 API

       5.1.5

Allegro reference manual                                                      al_register_trace_handler(3alleg5)

              #include <allegro5/allegro.h>

              void al_register_trace_handler(void (*handler)(char const *))