From: Rich Felker <dalias@libc.org>
To: Alexander Weps <exander77@pm.me>
Cc: musl@lists.openwall.com
Subject: Re: [musl] Broken mktime calculations when crossing DST boundary
Date: Mon, 25 Mar 2024 14:53:39 -0400 [thread overview]
Message-ID: <20240325185339.GG4163@brightrain.aerifal.cx> (raw)
In-Reply-To: <UR0Vya1hmBXvuPCcXsD_bEdmjRIYSZ8dbdt3ivdZxfdLASyfvp9ffpD7QPHLad2ZsOGQExkFKdmx6plvq0_eJPhY_PiGHd8Fv1-kUy_ToEg=@pm.me>
On Mon, Mar 25, 2024 at 06:28:14PM +0000, Alexander Weps wrote:
> On Monday, March 25th, 2024 at 19:02, Rich Felker <dalias@libc.org> wrote:
>
> > On Mon, Mar 25, 2024 at 09:42:53AM -0400, Rich Felker wrote:
> >
> > > On Mon, Mar 25, 2024 at 01:24:57PM +0000, Alexander Weps wrote:
> > >
> > > > See below.
> > > >
> > > > AW
> > > >
> > > > On Monday, March 25th, 2024 at 14:13, Rich Felker dalias@libc.org wrote:
> > > >
> > > > > On Mon, Mar 25, 2024 at 12:55:28PM +0000, Alexander Weps wrote:
> > > > >
> > > > > > > If you take your test program and switch it to initialize with
> > > > > > > tm_mday=31, then do -=1 instead of +=1, you'll find that it gives
> > > > > > > 2011-12-29 01:00:00 -10 as well, only now it seems like the correct,
> > > > > > > expected thing to happen. Any change to "fix" the case you're
> > > > > > > complaining about would necessarily break this case.
> > > > > >
> > > > > > So (- day, +day):
> > > > > >
> > > > > > Musl:
> > > > > > 2011-12-31 01:00:00 +14
> > > > > > 2011-12-29 01:00:00 -10
> > > > > > 2011-12-29 01:00:00 -10
> > > > > >
> > > > > > Glibc:
> > > > > > 2012-01-01 01:00:00 +14
> > > > > > 2011-12-31 01:00:00 +14
> > > > > > 2012-01-01 01:00:00 +14
> > > > > >
> > > > > > Seems like musl doesn't even interpret the initial struct tm
> > > > > > correctly in that case. It is off by day.
> > > > > >
> > > > > > Because December only had 30 days, 31s day after normalization is
> > > > > > January 1st.
> > > > >
> > > > > This is nonsense. December has a day 31, which you can clearly see
> > > > > from the glibc output. For this particular year in this zone, with the
> > > > > zone rule change, there are "only 30 days" in December, but they are
> > > > > numbered 1-29 and 31, not 1-30.
> > > >
> > > > You confuse day of month which is represented in tm_mday with
> > > > calendar day that is interpreted by strftime.
> > > >
> > > > You said to set tm_mday = 31, which would be January 1st after normalization.
> > > > December 31s is 30th day of month represented as tm_mday = 30.
> > >
> > > OK, I meant tm_mday=31-1.
> >
> >
> > Um, no, where did you get that idea? I just assumed you were right
> > because I always forget which tm_* are off-by-1, but tm_mday is
> > one-based not zero-based:
> >
> > int tm_mday; // day of the month -- [1, 31]
> >
> > (per the standard). So how did you end up getting the wrong thing? Are
> > you even running the code you say you are?
> >
>
> I have to sincerely ask if you are feeling ok?
> You seem not able to follow this conversation.
>
> What idea do you mean?
> Also you have the codes. You can like "I don't know" run them yourself?
> You question I run those codes without trying to run them yourself? Again?!
> What is going on?
The first few pieces of code you posted did not work because they
depended on other code you did not include, so I stopped trying to run
them.
> Maybe I reiterate some basic facts for you and that will put you
> back on track.
>
> This was an example from an article provided earlier in this thread (by somebody).
> We are in TZ=Pacific/Apia.
> The 30th December was skipped in 2011. There was no December 30th.
> So, there were only 30 days in December.
> 30th day of the month December was December 31st.
>
> And run those examples yourself. I have no idea why I am being
> questioned if they generate the output when you can easily verify it
> yourself.
Which piece of self-contained, actually-runnable code would you like
me to look at that demonstrates something wrong? (i.e. not something I
have already said is behaving as expected)
Rich
next prev parent reply other threads:[~2024-03-25 18:53 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-24 13:36 Alexander Weps
2024-03-24 16:59 ` Alexander Weps
2024-03-24 17:04 ` Rich Felker
2024-03-24 17:12 ` Alexander Weps
2024-03-24 18:00 ` Alexander Weps
2024-03-24 18:02 ` Rich Felker
2024-03-24 18:16 ` Alexander Weps
2024-03-24 18:24 ` Rich Felker
2024-03-24 18:36 ` Alexander Weps
2024-03-24 19:01 ` Joakim Sindholt
2024-03-24 19:05 ` Alexander Weps
2024-03-24 19:06 ` Alexander Weps
2024-03-24 19:13 ` Alexander Weps
2024-03-24 19:13 ` Alexander Weps
2024-03-24 19:22 ` Rich Felker
2024-03-24 19:57 ` Alexander Weps
2024-03-24 20:22 ` Rich Felker
2024-03-24 20:50 ` Alexander Weps
2024-03-24 21:43 ` Alexander Weps
2024-03-24 23:51 ` Thorsten Glaser
2024-03-25 0:36 ` Alexander Weps
2024-03-25 11:52 ` Alexander Weps
2024-03-25 12:21 ` Rich Felker
2024-03-25 12:55 ` Alexander Weps
2024-03-25 13:08 ` Rich Felker
2024-03-25 13:13 ` Alexander Weps
2024-03-25 13:13 ` Rich Felker
2024-03-25 13:24 ` Alexander Weps
2024-03-25 13:42 ` Rich Felker
2024-03-25 13:48 ` Alexander Weps
2024-03-25 13:50 ` Alexander Weps
2024-03-25 18:02 ` Rich Felker
2024-03-25 18:28 ` Alexander Weps
2024-03-25 18:53 ` Rich Felker [this message]
2024-03-25 18:57 ` Alexander Weps
2024-03-25 19:38 ` Rich Felker
2024-03-25 19:47 ` Rich Felker
2024-03-25 20:05 ` Alexander Weps
2024-03-25 20:12 ` Alexander Weps
2024-03-25 20:00 ` Alexander Weps
2024-03-25 20:23 ` Rich Felker
2024-03-25 20:31 ` Rich Felker
2024-03-25 23:19 ` Thorsten Glaser
2024-03-25 23:16 ` Thorsten Glaser
2024-03-25 13:44 ` Alexander Weps
2024-03-25 22:40 ` Thorsten Glaser
2024-03-25 22:59 ` Alexander Weps
2024-03-25 23:34 ` Thorsten Glaser
2024-03-26 12:45 ` Alexander Weps
2024-03-26 21:59 ` Thorsten Glaser
2024-03-27 0:14 ` Alexander Weps
2024-03-27 0:38 ` Alexander Weps
2024-03-27 1:35 ` Thorsten Glaser
2024-03-27 2:45 ` Alexander Weps
2024-03-27 4:42 ` Thorsten Glaser
2024-03-26 18:56 ` Alexander Weps
2024-03-25 23:13 ` Rich Felker
-- strict thread matches above, loose matches on Subject: below --
2024-03-22 19:56 Alexander Weps
2024-03-23 6:41 ` Markus Wichmann
[not found] ` <528SeRFaPfDw7fA4kqKDlio1U4RB_t9nmUemPcWw9_t1e2hBDpXYFmOqxAC37szgYvAVtmTuXWsmT64SSN3cSQFVdrQqXUAgkdTMPZQ0bg0=@pm.me>
2024-03-23 10:38 ` Markus Wichmann
2024-03-23 11:59 ` Alexander Weps
2024-03-23 12:00 ` Alexander Weps
2024-03-23 12:31 ` Rich Felker
2024-03-23 13:49 ` Alexander Weps
2024-03-23 15:31 ` Rich Felker
2024-03-23 16:54 ` Alexander Weps
2024-03-23 18:57 ` Alexander Weps
2024-03-23 19:33 ` Alexander Weps
2024-03-23 20:18 ` Rich Felker
2024-03-23 20:40 ` Alexander Weps
2024-03-24 0:36 ` Eric Pruitt
2024-03-24 2:04 ` Rich Felker
2024-03-24 3:32 ` Daniel Gutson
2024-03-24 11:05 ` Alexander Weps
2024-03-24 13:24 ` Alexander Weps
2024-03-23 12:01 ` Alexander Weps
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