al_trace - Man Page

#include <allegro.h>

void al_trace(const char *msg, ...);

Outputs a debugging trace message, using a printf() format string given  in ASCII. If you have installed a custom trace handler it uses that, or  if the environment variable ALLEGRO_TRACE is set it writes into the file  specified by the environment, otherwise it writes the message to  "allegro.log" in the current directory. You will usually want to use the  TRACE() macro instead of calling this function directly.

TRACE(3), al_assert(3), register_trace_handler(3)

al_assert(3), register_trace_handler(3), TRACE(3).