* bug#7337: 23.2; (require 'time) changes timezone
@ 2010-11-05 21:46 Kevin Ryde
2010-11-08 18:01 ` Stefan Monnier
0 siblings, 1 reply; 7+ messages in thread
From: Kevin Ryde @ 2010-11-05 21:46 UTC (permalink / raw
To: 7337
Doing a (require 'time) changes the `current-time-zone' to the system
default per a (set-time-zone-rule nil). I think that loading a .el
shouldn't change the zone. The effect can be seen from "emacs -Q"
(let (before after)
(set-time-zone-rule "ABC+1")
(setq before (current-time-zone))
(require 'time)
(setq after (current-time-zone))
(list (car before) (car after)))
=> (-3600 39600)
where I expected
=> (-3600 -3600)
which is what happens if evaluated a second time, since (require 'time)
is then a no-op.
I suppose it comes from display-time-world-list probing whether the
Olson timezone names are known to the C library. I think it should save
and restore the existing TZ the way `add-change-log-entry' and
`time-stamp-string' do.
For some of my own code lately I tried a macro to hide the details and
the unwind-protect a bit. Perhaps a name like with-time-zone-rule or
with-temporary-time-zone-rule would match set-time-zone-rule better than
"...-TZ".
(defmacro xtide-with-TZ (tz &rest body)
"Run BODY with `set-time-zone-rule' temporarily to TZ.
The current timezone (per `getenv' \"TZ\") is restored by an
`unwind-protect'."
(declare (indent 1))
`(let ((xtide-with-TZ--old (getenv "TZ")))
(set-time-zone-rule ,tz)
(unwind-protect
(progn ,@body)
(set-time-zone-rule xtide-with-TZ--old))))
In GNU Emacs 23.2.1 (i486-pc-linux-gnu, GTK+ Version 2.20.0)
of 2010-05-16 on raven, modified by Debian
configured using `configure '--build' 'i486-linux-gnu' '--build' 'i486-linux-gnu' '--prefix=/usr' '--sharedstatedir=/var/lib' '--libexecdir=/usr/lib' '--localstatedir=/var/lib' '--infodir=/usr/share/info' '--mandir=/usr/share/man' '--with-pop=yes' '--enable-locallisppath=/etc/emacs23:/etc/emacs:/usr/local/share/emacs/23.2/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/23.2/site-lisp:/usr/share/emacs/site-lisp:/usr/share/emacs/23.2/leim' '--with-x=yes' '--with-x-toolkit=gtk' '--with-toolkit-scroll-bars' 'build_alias=i486-linux-gnu' 'CFLAGS=-DDEBIAN -g -O2' 'LDFLAGS=-g' 'CPPFLAGS=''
Important settings:
value of $LC_ALL: nil
value of $LC_COLLATE: nil
value of $LC_CTYPE: nil
value of $LC_MESSAGES: nil
value of $LC_MONETARY: nil
value of $LC_NUMERIC: nil
value of $LC_TIME: nil
value of $LANG: en_AU
value of $XMODIFIERS: nil
locale-coding-system: iso-latin-1-unix
default enable-multibyte-characters: t
^ permalink raw reply [flat|nested] 7+ messages in thread
* bug#7337: 23.2; (require 'time) changes timezone
2010-11-05 21:46 bug#7337: 23.2; (require 'time) changes timezone Kevin Ryde
@ 2010-11-08 18:01 ` Stefan Monnier
2010-11-09 0:36 ` Kevin Ryde
2011-07-14 14:43 ` Lars Magne Ingebrigtsen
0 siblings, 2 replies; 7+ messages in thread
From: Stefan Monnier @ 2010-11-08 18:01 UTC (permalink / raw
To: Kevin Ryde; +Cc: 7337
> Doing a (require 'time) changes the `current-time-zone' to the system
> default per a (set-time-zone-rule nil). I think that loading a .el
> shouldn't change the zone. The effect can be seen from "emacs -Q"
> (let (before after)
> (set-time-zone-rule "ABC+1")
> (setq before (current-time-zone))
> (require 'time)
> (setq after (current-time-zone))
> (list (car before) (car after)))
> => (-3600 39600)
> where I expected
> => (-3600 -3600)
> which is what happens if evaluated a second time, since (require 'time)
> is then a no-op.
Indeed, that's a bug.
> I suppose it comes from display-time-world-list probing whether the
> Olson timezone names are known to the C library. I think it should save
> and restore the existing TZ the way `add-change-log-entry' and
> `time-stamp-string' do.
But do those two other uses work?
> For some of my own code lately I tried a macro to hide the details and
> the unwind-protect a bit. Perhaps a name like with-time-zone-rule or
> with-temporary-time-zone-rule would match set-time-zone-rule better than
> "...-TZ".
> (defmacro xtide-with-TZ (tz &rest body)
> "Run BODY with `set-time-zone-rule' temporarily to TZ.
> The current timezone (per `getenv' \"TZ\") is restored by an
> `unwind-protect'."
> (declare (indent 1))
> `(let ((xtide-with-TZ--old (getenv "TZ")))
> (set-time-zone-rule ,tz)
> (unwind-protect
> (progn ,@body)
> (set-time-zone-rule xtide-with-TZ--old))))
And similar does this code work for you? In my tests, (getenv "TZ")
just always returns nil. So it seems we'd need to add a new function
time-zone-rule to get the current time-zone rule. Or else we could
make set-time-zone-rule return the previous time-zone rule.
Stefan
^ permalink raw reply [flat|nested] 7+ messages in thread
* bug#7337: 23.2; (require 'time) changes timezone
2010-11-08 18:01 ` Stefan Monnier
@ 2010-11-09 0:36 ` Kevin Ryde
2010-11-18 0:16 ` Kevin Ryde
2011-08-08 15:55 ` Chong Yidong
2011-07-14 14:43 ` Lars Magne Ingebrigtsen
1 sibling, 2 replies; 7+ messages in thread
From: Kevin Ryde @ 2010-11-09 0:36 UTC (permalink / raw
To: Stefan Monnier; +Cc: 7337
Stefan Monnier <monnier@iro.umontreal.ca> writes:
>
> But do those two other uses work?
Oh, they might be dodgy too. I suppose set-time-zone-rule changes the C
level environ[], but the lisp `getenv' looks in the process-environment
variable, not environ[]. Does that sound right? Should
set-time-zone-rule set TZ in process-environment?
^ permalink raw reply [flat|nested] 7+ messages in thread
* bug#7337: 23.2; (require 'time) changes timezone
2010-11-09 0:36 ` Kevin Ryde
@ 2010-11-18 0:16 ` Kevin Ryde
2011-08-08 15:55 ` Chong Yidong
1 sibling, 0 replies; 7+ messages in thread
From: Kevin Ryde @ 2010-11-18 0:16 UTC (permalink / raw
To: 7337
I wrote:
>
> lisp `getenv' ... TZ
Perhaps it should effectively be a save-and-restore of getenv TZ, since
setenv TZ does the set-time-zone-rule (in emacs22 up).
(let ((old (getenv "TZ")))
(setenv "TZ" new)
(unwind-protect
(...)
(setenv "TZ" old)))
Which would still lose any set-time-zone-rule that had not been
accompanied by a (setenv "TZ"). But if you've got TZ in the C environ[]
and lisp process-environment out of sync then there's probably going to
be trouble no matter what.
^ permalink raw reply [flat|nested] 7+ messages in thread
* bug#7337: 23.2; (require 'time) changes timezone
2010-11-08 18:01 ` Stefan Monnier
2010-11-09 0:36 ` Kevin Ryde
@ 2011-07-14 14:43 ` Lars Magne Ingebrigtsen
2011-07-15 0:40 ` Kevin Ryde
1 sibling, 1 reply; 7+ messages in thread
From: Lars Magne Ingebrigtsen @ 2011-07-14 14:43 UTC (permalink / raw
To: Stefan Monnier; +Cc: 7337, Kevin Ryde
Stefan Monnier <monnier@iro.umontreal.ca> writes:
> And similar does this code work for you? In my tests, (getenv "TZ")
> just always returns nil. So it seems we'd need to add a new function
> time-zone-rule to get the current time-zone rule. Or else we could
> make set-time-zone-rule return the previous time-zone rule.
Hm. Would that be returning the tzname variable (as described in the
tzet manual page)?
--
(domestic pets only, the antidote for overdose, milk.)
bloggy blog http://lars.ingebrigtsen.no/
^ permalink raw reply [flat|nested] 7+ messages in thread
* bug#7337: 23.2; (require 'time) changes timezone
2011-07-14 14:43 ` Lars Magne Ingebrigtsen
@ 2011-07-15 0:40 ` Kevin Ryde
0 siblings, 0 replies; 7+ messages in thread
From: Kevin Ryde @ 2011-07-15 0:40 UTC (permalink / raw
To: Lars Magne Ingebrigtsen; +Cc: 7337
Lars Magne Ingebrigtsen <larsi@gnus.org> writes:
>
> Hm. Would that be returning the tzname variable (as described in the
> tzet manual page)?
Probably not, perhaps the TZ entry the C-level environ[], if that's
essentially what set-time-zone-rule writes to.
I later changed the macro I posted to the bit below, doing a `setenv' on
restoring as well as `set-time-zone-rule'. I suspect set-time-zone-rule
might update the lisp process-environment as well as the C environ[]
... but I'm not certain if that's right, or enough, for combinations of
save/restore and to influence the current process and/or spawned
subprocesses, etc etc.
(defmacro xtide-with-TZ (tz &rest body)
;; checkdoc-params: (tz body)
"Run BODY with `set-time-zone-rule' temporarily to TZ.
The current timezone (per `getenv' \"TZ\") is restored by an
`unwind-protect'.
This doesn't work properly if a `set-time-zone-rule' has been
applied but (setenv \"TZ\") not updated accordingly. A `setenv'
is done here so that `xtide-with-TZ' will nest successfully at
least."
;; This getenv and restore is similar to what add-log.el
;; `add-change-log-entry' and time-stamp.el `time-stamp-string' do. In
;; Emacs 23.2 the initializer in `display-time-world-list' always sets
;; back to nil, but a restore seems a much better idea.
;;
;; (setenv "TZ") makes the new TZ visible to a nested `xtide-with-TZ' or
;; to `add-change-log-entry'. As of Emacs 23.2 `set-time-zone-rule'
;; changes TZ in the C-level environ[], but not in the lisp level
;; `process-environment'.
;;
;; setenv in emacs22 up returns the value set, but in emacs21 and xemacs21
;; it's the whole new `process-environment', or some such, so don't depend
;; on the value.
;;
;; setenv in emacs22 up also calls `set-time-zone-rule' itself, but for
;; emacs21 and xemacs21 must do so explicitly
;;
(declare (indent 1)) ;; from 'cl
`(let ((xtide-with-TZ--old (getenv "TZ"))
(xtide-with-TZ--new ,tz)) ;; evaluate `tz' expression only once
(setenv "TZ" xtide-with-TZ--new)
(set-time-zone-rule xtide-with-TZ--new)
(unwind-protect
(progn ,@body)
(setenv "TZ" xtide-with-TZ--old)
(set-time-zone-rule xtide-with-TZ--old))))
^ permalink raw reply [flat|nested] 7+ messages in thread
* bug#7337: 23.2; (require 'time) changes timezone
2010-11-09 0:36 ` Kevin Ryde
2010-11-18 0:16 ` Kevin Ryde
@ 2011-08-08 15:55 ` Chong Yidong
1 sibling, 0 replies; 7+ messages in thread
From: Chong Yidong @ 2011-08-08 15:55 UTC (permalink / raw
To: Kevin Ryde; +Cc: 7337
Kevin Ryde <user42@zip.com.au> writes:
> Oh, they might be dodgy too. I suppose set-time-zone-rule changes the C
> level environ[], but the lisp `getenv' looks in the process-environment
> variable, not environ[]. Does that sound right? Should
> set-time-zone-rule set TZ in process-environment?
Yes, Lisp code should typically use (setenv "TZ" ...) rather than
set-time-zone-rule for this reason. I have updated the doc of
set-time-zone-rule, and changed the users of set-time-zone-rule
accordingly.
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2011-08-08 15:55 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2010-11-05 21:46 bug#7337: 23.2; (require 'time) changes timezone Kevin Ryde
2010-11-08 18:01 ` Stefan Monnier
2010-11-09 0:36 ` Kevin Ryde
2010-11-18 0:16 ` Kevin Ryde
2011-08-08 15:55 ` Chong Yidong
2011-07-14 14:43 ` Lars Magne Ingebrigtsen
2011-07-15 0:40 ` Kevin Ryde
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