Allow outputting logs to stdout via the ALLEGRO_TRACE env variable.

Author: SiegeLordEx

allegro5.cfg

@@ -186,6 +186,9 @@ channels=all
 # Log-level. Can be one of debug, info, warn, error, none or empty.
 # In debug builds if it is empty or unset, then the level is set to debug.
 # In release builds if it is empty or unset, then the level is set to none.
+# If not none, Allegro will write out the logs to an allegro.log file next to
+# the binary. Use ALLEGRO_TRACE environment variable to control that file
+# location. A special filename of - (dash) means logging to stdout.
 level=
 
 # Set to 0 to disable line numbers in log files.

src/debug.c

@@ -36,6 +36,7 @@ typedef struct TRACE_INFO
 {
    bool trace_virgin;
    FILE *trace_file;
+   bool need_close;
    _AL_MUTEX trace_mutex;
 
    /* 0: debug, 1: info, 2: warn, 3: error */
@@ -54,6 +55,7 @@ static TRACE_INFO trace_info =
 {
    true,
    NULL,
+   true,
    _AL_MUTEX_UNINITED,
    0,
    7,
@@ -173,8 +175,15 @@ static void open_trace_file(void)
    if (trace_info.trace_virgin) {
       const char *s = getenv("ALLEGRO_TRACE");
 
-      if (s)
-         trace_info.trace_file = fopen(s, "w");
+      if (s) {
+         if (!strcmp(s, "-")) {
+            trace_info.trace_file = stdout;
+            trace_info.need_close = false;
+         }
+         else {
+            trace_info.trace_file = fopen(s, "w");
+         }
+      }
       else
 #if defined(ALLEGRO_IPHONE) || defined(ALLEGRO_ANDROID) || defined(__EMSCRIPTEN__)
          /* iPhone and Android don't like us writing files, so we'll be doing
@@ -342,7 +351,7 @@ void _al_shutdown_logging(void)
       trace_info.configured = false;
    }
 
-   if (trace_info.trace_file) {
+   if (trace_info.trace_file && trace_info.need_close) {
       fclose(trace_info.trace_file);
    }