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

diff --git a/lib-src/ChangeLog b/lib-src/ChangeLog
index 6f4f3cd86e3e68045a4932767ba9439e50a15a05..88c30989c75fe403d839d8bce7d23135cacc8845 100644 (file)
--- 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        (lock_file): Fix test for out-of-date lock file; it was reversed.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>