[PATCH] emacs: derive correct timestamp in FCC unique name
Tomi Ollila
tomi.ollila at iki.fi
Thu Jun 14 02:43:37 PDT 2012
On Wed, Jun 13 2012, Jesse Rosenthal <jrosenthal at jhu.edu> wrote:
> Previously, the timestamp at the beginning of the FCC maildir unique
> maildir name was derived incorrectly, thanks to an integer
> overflow. This changes the derivation of timestamp to float
> arithmetic, and so gets the number correct. (It is still formatted
> with "%d" so it will show up as an integer.)
>
> This change is mostly a question of consistency, since the unique name
> is arbitrary anyway. But since most people use timestamps, and that was
> the original intention here as well, we might as well.
>
> Signed-off-by: Jesse Rosenthal <jrosenthal at jhu.edu>
> ---
Good point -- did some experiments (on 32bit machine, on 64 (* 65536 *65536)
just works OK (4294967296).
(insert (format " %d" (* 8191 65536))) 536805376
(insert (format " %d" (* 8192 65536))) -536870912
Wraps now (many times already)
(insert (format " %d" (* 32767 65536.0))) 2147418112
(insert (format " %d" (* 32768 65536.0))) -2147483648
Wraps Tue Jan 19 03:14:08 2038 UTC
(insert (format " %0.f" (* 32768 65536.0))) 2147483648
(insert (format " %0.f" (* 65536 65536.0))) 4294967296
Does not wrap.
On emacs window you can re-experiment by typing C-x C-e after last
closing ')' on line.
(float-time '(32767 65536)) -> 2147418112.0 (minibuffer output)
(float-time '(32768 65536)) -> error "Invalid time specification"
On 64-bit machine this latest work ok; i.e 2147483648.0 is returned.
Alternatives:
1) Use current patch, filenames will have extra '-' in 2038 on 32-bit
systems.
2) Drop 'timeid' and replace it with (float-time) in `format` call a few
lines in original source after the patch context below -- No idea
how (float-time) works on 32-bit systems after 2038.
3) Use "%0.f" in format string instead of "%d" (there is no "%ld" or "%u"
sequences for `format`. I wonder what (current-time-string) in current
emacs return in 2038 (maybe I test (sometime(tm)) with (lib)faketime).
I suggest option #2.
Tomi
> emacs/notmuch-maildir-fcc.el | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/emacs/notmuch-maildir-fcc.el b/emacs/notmuch-maildir-fcc.el
> index dcfbc4b..6fd8ff9 100644
> --- a/emacs/notmuch-maildir-fcc.el
> +++ b/emacs/notmuch-maildir-fcc.el
> @@ -141,7 +141,7 @@ will NOT be removed or replaced."
>
> (defun notmuch-maildir-fcc-make-uniq-maildir-id ()
> (let* ((ct (current-time))
> - (timeid (+ (* (car ct) 65536) (cadr ct)))
> + (timeid (+ (* (car ct) 65536.0) (cadr ct)))
> (microseconds (car (cdr (cdr ct))))
> (hostname (notmuch-maildir-fcc-host-fixer system-name)))
> (setq notmuch-maildir-fcc-count (+ notmuch-maildir-fcc-count 1))
> --
> 1.7.9.5
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