Documentation, small fixes
diff --git a/debug.h b/debug.h
index e3749ff..7a9761b 100644
--- a/debug.h
+++ b/debug.h
@@ -18,6 +18,6 @@
 #  if defined __STDC_VERSION__ && __STDC_VERSION__ >= 199901L
 #   define DEBUG_FUNCTION	__func__
 #  else
-#   define DEBUG_FUNCTION	((__const char *) 0)
+#   define DEBUG_FUNCTION	"???"
 #  endif
 # endif