Document 2014-01-22T19:02:41Z!eggert@cs.ucla.edu better.

1 files changed, 19 insertions, 5 deletions

diff --git a/lib-src/ChangeLog b/lib-src/ChangeLog
index 6f4f3cd86e3..88c30989c75 100644
--- a/lib-src/ChangeLog
+++ b/lib-src/ChangeLog
@@ -7,13 +7,27 @@
 
         Fix miscellaneous update-game-score bugs.
         * update-game-score.c (difftime) [!HAVE_DIFFTIME]: Remove.
-        (read_score) [HAVE_GETDELIM]: Don't access uninitialized storage.
-        (read_scores, write_scores): Check for fclose failure.
+        (read_score) [HAVE_GETDELIM]: Don't access uninitialized storage,
+        as that leads to undefined behavior, which is a bad thing
+        particularly in a setuid program.
+        (read_scores, write_scores): Check for fclose failure; on some
+        systems, I/O errors are not reported by primitives like getc and
+        putc, but instead are delayed until fclose, so fclose failures
+        should be diagnosed like other read and write errors.
         (write_scores): Use fchmod, not chmod, to avoid a race.
+        Otherwise, if the lock is broken by some other process,
+        update-game-score might try to change the permission on someone
+        else's file or on a nonexistent file, and incorrectly report an
+        error when this fails.
         (lock_file): Fix test for out-of-date lock file; it was reversed.
-        Use ordinary subtraction rather than difftime; since we're already
-        assuming POSIX we don't need to worry about the possibility of
-        time_t being a magic cookie.
+        That is, it incorrectly broke locks when they were more than an
+        hour into the future, instead of when they were more than an hour
+        in the past.  Use ordinary subtraction rather than difftime; since
+        we're already assuming POSIX we don't need to worry about the
+        possibility of time_t being a magic cookie, and since timestamps
+        are positive we don't need to worry about integer overflow when
+        subtracting them.  Put two spaces, not just one, after a sentence
+        end in a comment.
 
 2014-01-19  Paul Eggert  <eggert@cs.ucla.edu>