Use unsigned arithmetic for sequence comparison.

2 files changed, 8 insertions, 1 deletions

diff --git a/ChangeLog b/ChangeLog
index ce89b5b..4190484 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
 2009-08-27  Gary Wong  <gtw@gnu.org>
 
+	* gwm.c (sync_with_callback): Perform the sequence comparison
+	with unsigned arithmetic, so that overflow semantics are
+	well-defined.
+
+2009-08-27  Gary Wong  <gtw@gnu.org>
+
 	* frame.c (recalc_size): Implement edge resistance when resizing
 	frames.
 	(edge_resist): New function.
diff --git a/gwm.c b/gwm.c
index 7246679..ba30d72 100644
--- a/gwm.c
+++ b/gwm.c
@@ -25,6 +25,7 @@
 
 #include <assert.h>
 #include <errno.h>
+#include <limits.h>
 #if HAVE_MCHECK_H
 #include <mcheck.h>
 #endif
@@ -264,7 +265,7 @@ static void check_async_callbacks( void ) {
 
 extern void sync_with_callback( unsigned int sequence ) {
 
-    while( queue_head && (int) sequence - (int) queue_head->sequence >= 0 ) {
+    while( queue_head && sequence - queue_head->sequence < UINT_MAX >> 1 ) {
 	struct async_callback *entry = queue_head;
 	xcb_generic_error_t *error;
 	void *reply = xcb_wait_for_reply( c, entry->sequence, &error );