bug#6830: widget-complete bad completions in :type 'file

[Paul Eggert <eggert@cs.ucla.edu>]

That patch assumes that s1 != s2.  This assumption about qsort
is quite likely true on Windows but it's not guaranteed by
the C standard, and for portability it's better to play it safe
and stick with the pattern that's already in the code.
I installed this further patch:

=== modified file 'src/ChangeLog'
--- src/ChangeLog	2012-03-12 06:34:32 +0000
+++ src/ChangeLog	2012-03-12 08:27:25 +0000
@@ -1,3 +1,7 @@
+2012-03-12  Paul Eggert  <eggert@cs.ucla.edu>
+
+	* buffer.c (compare_overlays): Don't assume args differ (Bug#6830).
+
 2012-03-12  Chong Yidong  <cyd@gnu.org>
 
 	* eval.c (inhibit_lisp_code): Rename from

=== modified file 'src/buffer.c'
--- src/buffer.c	2012-03-09 16:46:25 +0000
+++ src/buffer.c	2012-03-12 08:27:25 +0000
@@ -2868,7 +2868,9 @@
      between "equal" overlays.  The result can still change between
      invocations of Emacs, but it won't change in the middle of
      `find_field' (bug#6830).  */
-  return XHASH (s1->overlay) < XHASH (s2->overlay) ? -1 : 1;
+  if (XHASH (s1->overlay) != XHASH (s2->overlay))
+    return XHASH (s1->overlay) < XHASH (s2->overlay) ? -1 : 1;
+  return 0;
 }
 
 /* Sort an array of overlays by priority.  The array is modified in place.