* [Qemu-devel] [PATCH] qemu_timedate_diff() shouldn't modify its argument.
@ 2011-11-06 16:00 Gleb Natapov
2011-11-07 19:09 ` Rik van Riel
` (2 more replies)
0 siblings, 3 replies; 5+ messages in thread
From: Gleb Natapov @ 2011-11-06 16:00 UTC (permalink / raw)
To: qemu-devel
The caller of qemu_timedate_diff() does not expect that tm it passes to
the function will be modified, but mktime() is destructive and modifies
its argument. Pass a copy of tm to it and set tm_isdst so that mktime()
will not rely on it since its value may be outdated.
Signed-off-by: Gleb Natapov <gleb@redhat.com>
diff --git a/vl.c b/vl.c
index 624da0f..641629b 100644
--- a/vl.c
+++ b/vl.c
@@ -460,8 +460,11 @@ int qemu_timedate_diff(struct tm *tm)
if (rtc_date_offset == -1)
if (rtc_utc)
seconds = mktimegm(tm);
- else
- seconds = mktime(tm);
+ else {
+ struct tm tmp = *tm;
+ tmp.tm_isdst = -1; /* use timezone to figure it out */
+ seconds = mktime(&tmp);
+ }
else
seconds = mktimegm(tm) + rtc_date_offset;
--
Gleb.
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [Qemu-devel] [PATCH] qemu_timedate_diff() shouldn't modify its argument.
2011-11-06 16:00 [Qemu-devel] [PATCH] qemu_timedate_diff() shouldn't modify its argument Gleb Natapov
@ 2011-11-07 19:09 ` Rik van Riel
2011-11-07 20:16 ` Ronen Hod
2011-11-08 17:24 ` Anthony Liguori
2 siblings, 0 replies; 5+ messages in thread
From: Rik van Riel @ 2011-11-07 19:09 UTC (permalink / raw)
To: qemu-devel
On 11/06/2011 11:00 AM, Gleb Natapov wrote:
> The caller of qemu_timedate_diff() does not expect that tm it passes to
> the function will be modified, but mktime() is destructive and modifies
> its argument. Pass a copy of tm to it and set tm_isdst so that mktime()
> will not rely on it since its value may be outdated.
Ohhh, nice catch.
> Signed-off-by: Gleb Natapov<gleb@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
--
All rights reversed
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Qemu-devel] [PATCH] qemu_timedate_diff() shouldn't modify its argument.
2011-11-06 16:00 [Qemu-devel] [PATCH] qemu_timedate_diff() shouldn't modify its argument Gleb Natapov
2011-11-07 19:09 ` Rik van Riel
@ 2011-11-07 20:16 ` Ronen Hod
2011-11-08 7:36 ` Gleb Natapov
2011-11-08 17:24 ` Anthony Liguori
2 siblings, 1 reply; 5+ messages in thread
From: Ronen Hod @ 2011-11-07 20:16 UTC (permalink / raw)
To: Gleb Natapov; +Cc: qemu-devel
On 11/06/2011 06:00 PM, Gleb Natapov wrote:
> The caller of qemu_timedate_diff() does not expect that tm it passes to
> the function will be modified, but mktime() is destructive and modifies
> its argument. Pass a copy of tm to it and set tm_isdst so that mktime()
> will not rely on it since its value may be outdated.
I believe that the original issue was not related to outdated data at
the moment of the daylight saving time transition.
using tmp.tm_isdst = -1 sounds good, but why use a copy of tm? The only
significant field that will change in the tm is the tm_isdst itself that
will be set to 0/1 (correctly).
Acked-by: Ronen Hod <rhod@redhat.com>
> Signed-off-by: Gleb Natapov<gleb@redhat.com>
> diff --git a/vl.c b/vl.c
> index 624da0f..641629b 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -460,8 +460,11 @@ int qemu_timedate_diff(struct tm *tm)
> if (rtc_date_offset == -1)
> if (rtc_utc)
> seconds = mktimegm(tm);
> - else
> - seconds = mktime(tm);
> + else {
> + struct tm tmp = *tm;
> + tmp.tm_isdst = -1; /* use timezone to figure it out */
> + seconds = mktime(&tmp);
> + }
> else
> seconds = mktimegm(tm) + rtc_date_offset;
>
> --
> Gleb.
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Qemu-devel] [PATCH] qemu_timedate_diff() shouldn't modify its argument.
2011-11-07 20:16 ` Ronen Hod
@ 2011-11-08 7:36 ` Gleb Natapov
0 siblings, 0 replies; 5+ messages in thread
From: Gleb Natapov @ 2011-11-08 7:36 UTC (permalink / raw)
To: Ronen Hod; +Cc: qemu-devel
On Mon, Nov 07, 2011 at 10:16:29PM +0200, Ronen Hod wrote:
> On 11/06/2011 06:00 PM, Gleb Natapov wrote:
> >The caller of qemu_timedate_diff() does not expect that tm it passes to
> >the function will be modified, but mktime() is destructive and modifies
> >its argument. Pass a copy of tm to it and set tm_isdst so that mktime()
> >will not rely on it since its value may be outdated.
>
> I believe that the original issue was not related to outdated data
> at the moment of the daylight saving time transition.
Don't know what do you mean here. The problem is definitely related to
incorrect data about daylight saving time.
> using tmp.tm_isdst = -1 sounds good, but why use a copy of tm? The
Hmm, what is not clear about "qemu_timedate_diff() shouldn't modify its
argument"? :)
> only significant field that will change in the tm is the tm_isdst
> itself that will be set to 0/1 (correctly).
This is incorrect (read man), but event if it would breed a new kind of
especially handsome ponies, if this is what caller wants it should call
mktime() by itself and not be a side effect of some random function
call.
>
> Acked-by: Ronen Hod <rhod@redhat.com>
>
> >Signed-off-by: Gleb Natapov<gleb@redhat.com>
> >diff --git a/vl.c b/vl.c
> >index 624da0f..641629b 100644
> >--- a/vl.c
> >+++ b/vl.c
> >@@ -460,8 +460,11 @@ int qemu_timedate_diff(struct tm *tm)
> > if (rtc_date_offset == -1)
> > if (rtc_utc)
> > seconds = mktimegm(tm);
> >- else
> >- seconds = mktime(tm);
> >+ else {
> >+ struct tm tmp = *tm;
> >+ tmp.tm_isdst = -1; /* use timezone to figure it out */
> >+ seconds = mktime(&tmp);
> >+ }
> > else
> > seconds = mktimegm(tm) + rtc_date_offset;
> >
> >--
> > Gleb.
> >
--
Gleb.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Qemu-devel] [PATCH] qemu_timedate_diff() shouldn't modify its argument.
2011-11-06 16:00 [Qemu-devel] [PATCH] qemu_timedate_diff() shouldn't modify its argument Gleb Natapov
2011-11-07 19:09 ` Rik van Riel
2011-11-07 20:16 ` Ronen Hod
@ 2011-11-08 17:24 ` Anthony Liguori
2 siblings, 0 replies; 5+ messages in thread
From: Anthony Liguori @ 2011-11-08 17:24 UTC (permalink / raw)
To: Gleb Natapov; +Cc: qemu-devel
On 11/06/2011 10:00 AM, Gleb Natapov wrote:
> The caller of qemu_timedate_diff() does not expect that tm it passes to
> the function will be modified, but mktime() is destructive and modifies
> its argument. Pass a copy of tm to it and set tm_isdst so that mktime()
> will not rely on it since its value may be outdated.
>
> Signed-off-by: Gleb Natapov<gleb@redhat.com>
Applied. Thanks.
Regards,
Anthony Liguori
> diff --git a/vl.c b/vl.c
> index 624da0f..641629b 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -460,8 +460,11 @@ int qemu_timedate_diff(struct tm *tm)
> if (rtc_date_offset == -1)
> if (rtc_utc)
> seconds = mktimegm(tm);
> - else
> - seconds = mktime(tm);
> + else {
> + struct tm tmp = *tm;
> + tmp.tm_isdst = -1; /* use timezone to figure it out */
> + seconds = mktime(&tmp);
> + }
> else
> seconds = mktimegm(tm) + rtc_date_offset;
>
> --
> Gleb.
>
>
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2011-11-08 17:25 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2011-11-06 16:00 [Qemu-devel] [PATCH] qemu_timedate_diff() shouldn't modify its argument Gleb Natapov
2011-11-07 19:09 ` Rik van Riel
2011-11-07 20:16 ` Ronen Hod
2011-11-08 7:36 ` Gleb Natapov
2011-11-08 17:24 ` Anthony Liguori
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