bug#7489: [coreutils] over aggressive threads in sort

[Paul Eggert]

Could you please try this little patch?  It should fix your
problem.  I came up with this fix in my sleep (literally!
I woke up this morning and the patch was in my head), but
haven't had time to look at the code in this area to see
if it's the best fix.

Clearly there's at least one more bug as noted in my previous email
<http://lists.gnu.org/archive/html/bug-coreutils/2010-11/msg00216.html>
but I expect it's less likely to fire.

diff --git a/src/sort.c b/src/sort.c
index 7e25f6a..1aa1eb4 100644
--- a/src/sort.c
+++ b/src/sort.c
@@ -3226,13 +3226,13 @@ queue_pop (struct merge_node_queue *queue)
 static void
 write_unique (struct line const *line, FILE *tfp, char const *temp_output)
 {
-  static struct line const *saved = NULL;
+  static struct line saved;
 
   if (!unique)
     write_line (line, tfp, temp_output);
-  else if (!saved || compare (line, saved))
+  else if (!saved.text || compare (line, &saved))
     {
-      saved = line;
+      saved = *line;
       write_line (line, tfp, temp_output);
     }
 }