Add a note about a questionable use of bool in xdisp.c

diff --git a/src/xdisp.c b/src/xdisp.c
index 85d356e9ba51f425891565012c90a1e66e2ef2bb..50c5518114e5d7403ea1f7b7de9c53eea609f00e 100644 (file)
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -10733,6 +10733,9 @@ display_echo_area (struct window *w)
      reset the echo_area_buffer in question to nil at the end because
      with_echo_area_buffer will sets it to an empty buffer.  */
   bool i = display_last_displayed_message_p;
+  /* According to the C99, C11 and C++11 standards, the integral value
+     of a "bool" is always 0 or 1, so this array access is safe here,
+     if oddly typed. */
   no_message_p = NILP (echo_area_buffer[i]);
 
   window_height_changed_p