GNU bug report logs - #8310
update-game-score -r logic broken with MAX_SCORES

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: bug-gnu-emacs <at> gnu.org
Subject: update-game-score -r logic broken with MAX_SCORES
Date: Mon, 21 Mar 2011 00:37:09 -0700

Here's a bug found by gcc -Wstrict-overflow (GCC 4.5.2) this one in
in update-game-score -r.  I plan to install the following patch.

update-game-score: fix bug with -r
* update-game-score.c (main): Don't set 'scores' to garbage when
-r is specified and scorecount != MAX_SCORES.  This bug was
introduced in the 2002-04-10 change, and was found with gcc
-Wstrict-overflow (GCC 4.5.2, x86-64).
=== modified file 'lib-src/update-game-score.c'
--- lib-src/update-game-score.c	2011-02-21 18:06:25 +0000
+++ lib-src/update-game-score.c	2011-03-21 07:17:22 +0000
@@ -242,13 +242,15 @@
   push_score (&scores, &scorecount, newscore, user_id, newdata);
   sort_scores (scores, scorecount, reverse);
   /* Limit the number of scores.  If we're using reverse sorting, then
-     we should increment the beginning of the array, to skip over the
-     *smallest* scores.  Otherwise, we just decrement the number of
-     scores, since the smallest will be at the end. */
+     also increment the beginning of the array, to skip over the
+     *smallest* scores.  Otherwise, just decrementing the number of
+     scores suffices, since the smallest is at the end. */
   if (scorecount > MAX_SCORES)
-    scorecount -= (scorecount - MAX_SCORES);
-  if (reverse)
-    scores += (scorecount - MAX_SCORES);
+    {
+      if (reverse)
+	scores += (scorecount - MAX_SCORES);
+      scorecount = MAX_SCORES;
+    }
   if (write_scores (scorefile, scores, scorecount) < 0)
     {
       unlock_file (scorefile, lockstate);

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