GNU bug report logs - #51228
Incorrect timezone in unified diff on Solaris?

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Vladimir Marek <Vladimir.Marek <at> oracle.com>
To: bug-diffutils <at> gnu.org
Subject: Incorrect timezone in unified diff on Solaris?
Date: Fri, 15 Oct 2021 15:55:17 +0200

[Message part 1 (text/plain, inline)]

Hi,

I believe that this is bug in diffutils, but I am not entirely sure. The
problem manifested itself while testing patchutils on Solaris. One of
the tests was failing. Upon closer inspection the filterdiff (aka
lsdiff) decides whether a give chunk is creating (or deleting) a file
based on timestamp the chunk is having. It compares whether the timezone
recorded equals to current timezone.

https://github.com/twaugh/patchutils/blob/master/src/filterdiff.c#L156

On Solaris patchutils correctly detect that there is no
struct tm ->  tm_gmtoff (HAVE_TM_GMTOFF). On line 1417 of nstrftime.c

 1415 #if HAVE_TM_GMTOFF
 1416             diff = tp->tm_gmtoff;
 1417 #else
 1418             if (!tz)
 1419               diff = 0;
 1420             else

And since there is zero tz specified in context.c

if (! (tm && nstrftime (buf, sizeof buf, time_format, tm, 0, nsec)))
                                                         ^^^

The resulting chunk has zero timezone offset (on Solaris). Like here:

$ TZ=EST+5 gdiff -urN dir.orig dir
diff -urN dir.orig/a dir/a
--- dir.orig/a  1969-12-31 19:00:00.000000000 +0000  <------ this file is missing
+++ dir/a       2021-10-14 12:24:20.785102347 +0000

On Linux and after my fix on Solaris the result is

--- dir.orig/a  1969-12-31 19:00:00.000000000 -0500

I am not entirely sure where is nstrftime.c coming from, so I'm
reporting the issue here. I am also attaching patch I plan to use on
Solaris. The patch and additional test works for me on diffutils 3.8 on
both Linux and Solaris.

Thanks for diffutils, I believe it's the most important tool for release
engineer :)

Cheers
-- 
	Vlad

[timezone.patch (text/plain, attachment)]

Message #10 received at 51228-done <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Vladimir Marek <Vladimir.Marek <at> oracle.com>
Cc: 51228-done <at> debbugs.gnu.org
Subject: Re: [bug-diffutils] bug#51228: Incorrect timezone in unified diff on
 Solaris?
Date: Fri, 15 Oct 2021 19:05:36 -0700

[Message part 1 (text/plain, inline)]

On 10/15/21 6:55 AM, Vladimir Marek wrote:

> I am not entirely sure where is nstrftime.c coming from, so I'm
> reporting the issue here.

Thanks for reporting it. Although nstrftime.c comes from Gnulib, this is 
a diffutils bug: the 0 diffutils passes to nstrftime stands for 
Universal Time (UT), whereas local time is wanted. This bug is not 
triggered on GNU/Linux or the BSDs, which have tm_gmtoff in their 
struct tm.

I installed the attached patch into diffutils. Please give it a try, as 
the patch you sent mishandles the case when today's UT offset differs 
from the UT offset in effect when the file was last modified (e.g., due 
to a daylight-saving change).

[0001-diff-fix-timezone-bug-on-Solaris.patch (text/x-patch, attachment)]

Message #13 received at 51228 <at> debbugs.gnu.org (full text, mbox):

From: Vladimir Marek <Vladimir.Marek <at> oracle.com>
To: 51228 <at> debbugs.gnu.org
Subject: Re: [External] : bug#51228: closed (Re: [bug-diffutils] bug#51228:
 Incorrect timezone in unified diff on Solaris?)
Date: Mon, 18 Oct 2021 16:28:10 +0200

[...]

> I installed the attached patch into diffutils. Please give it a try, as the
> patch you sent mishandles the case when today's UT offset differs from the
> UT offset in effect when the file was last modified (e.g., due to a
> daylight-saving change).

Your patch works fine for me, I'll gladly use it instead of my change.

Thank you
-- 
	Vlad

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