Re: Bug in UTC -> localtime conversion after 2038

[Jeff Johnston <jjohnstn@redhat.com>]

Thanks Ivan.  I added the patch manually as you didn't attach it, but made
you the author.  Patch applied.

-- Jeff J.

On Wed, Nov 4, 2020 at 11:21 AM Ivan Grokhotkov via Newlib <
newlib@sourceware.org> wrote:

>
>
> > On 4 Nov 2020, at 12:36, Udo de Boer <udo.de.boer@ubero.nl> wrote:
> >
> > [External: This email originated outside Espressif]
> >
> > Hi,
> >
> > UTC time to local timezone conversion did not work for years after 2038.
> > Daylight saving in the timezone was not recognized. Tested on 32bit
> > xtensa architecture with GCC 8.4 (esp32) and with 64bit time_t enabled.
> >
> > The struct tm is filled correct. So year, day etc are all filled with
> > the correct values. But the tm.tm_isdst is 0 and no daylight saving is
> > applied.
> >
> > It was caused by the following calculation in time/tzcalc_limits.c at
> > line 68
> >
> >       /* store the change-over time in GMT form by adding offset */
> >       tz->__tzrule[i].change = days * SECSPERDAY +
> >       tz->__tzrule[i].s + tz->__tzrule[i].offset;
> >
> > Here tz->__tzrule[i].change is a time_t (64bit). For some reason the
> > compiler does the calculation in 32 bit. All variables used in the
> > calculation are 32bit.
> >
> > I solved this locally by changing the lines to.
> >
> >       /* store the change-over time in GMT form by adding offset */
> >       tz->__tzrule[i].change = (time_t)days * SECSPERDAY +
> >       tz->__tzrule[i].s + tz->__tzrule[i].offset;
> >
> > Adding the cast time_t should not cause a problem when time_t is still
> > 32bit.
> >
> > I don't know if this is correct solution. I also only needed this
> > function. So more bugs like this could be hidden away in the time code.
> >
> >
> >
> >
> >
> >
> >
>
>
> Thank you for reporting and proposing the fix!
> Espressif will include this into the next esp32 toolchain release.
>
> For the convenience of the maintainers, I’ve attached the patch below.
>
>
> Best regards,
> Ivan Grokhotkov
>
>
>
> From 782c19cd861479cf09a4e2ee27bb7fec1872c626 Mon Sep 17 00:00:00 2001
> From: Ivan Grokhotkov <ivan@espressif.com>
> Date: Wed, 4 Nov 2020 16:49:51 +0100
> Subject: [PATCH] newlib: libc: fix 32-bit integer overflow when
> calculating TZ
>  rules
>
> ---
>  newlib/libc/time/tzcalc_limits.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/newlib/libc/time/tzcalc_limits.c
> b/newlib/libc/time/tzcalc_limits.c
> index e0ea6549c..00044a5d3 100644
> --- a/newlib/libc/time/tzcalc_limits.c
> +++ b/newlib/libc/time/tzcalc_limits.c
> @@ -66,7 +66,7 @@ __tzcalc_limits (int year)
>         }
>
>        /* store the change-over time in GMT form by adding offset */
> -      tz->__tzrule[i].change = days * SECSPERDAY +
> +      tz->__tzrule[i].change = (time_t) days * SECSPERDAY +
>        tz->__tzrule[i].s + tz->__tzrule[i].offset;
>      }
>
> --
> 2.21.0 (Apple Git-122)
>
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