From cae070000107848cd082496e14cf5851cc1f2c25 Mon Sep 17 00:00:00 2001
From: Stefan Monnier
Date: Fri, 9 Mar 2012 11:46:25 -0500
Subject: * src/buffer.c (compare_overlays): Avoid qsort's instability.

Fixes: debbugs:6830
---
 src/buffer.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

(limited to 'src/buffer.c')

diff --git a/src/buffer.c b/src/buffer.c
index 1577254d92a..efb9a80f35d 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -2864,7 +2864,11 @@ compare_overlays (const void *v1, const void *v2)
     return s1->beg < s2->beg ? -1 : 1;
   if (s1->end != s2->end)
     return s2->end < s1->end ? -1 : 1;
-  return 0;
+  /* Avoid the non-determinism of qsort by choosing an arbitrary ordering
+     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;
 }
 
 /* Sort an array of overlays by priority.  The array is modified in place.
-- 
cgit v1.2.1


From 9af5ed875659d596fcd5c84b7456ae4750cb3011 Mon Sep 17 00:00:00 2001
From: Paul Eggert
Date: Mon, 12 Mar 2012 01:27:25 -0700
Subject: * buffer.c (compare_overlays): Don't assume args differ (Bug#6830).

---
 src/buffer.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

(limited to 'src/buffer.c')

diff --git a/src/buffer.c b/src/buffer.c
index efb9a80f35d..1fea19b0d65 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -2868,7 +2868,9 @@ compare_overlays (const void *v1, const void *v2)
      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.
-- 
cgit v1.2.1