[Bug time/29951] New: daylight variable not set correctly if last DST change coincides with offset change

[Bug time/29951] New: daylight variable not set correctly if last DST change coincides with offset change

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=29951

            Bug ID: 29951
           Summary: daylight variable not set correctly if last DST change
                    coincides with offset change
           Product: glibc
           Version: 2.37
            Status: NEW
          Severity: normal
          Priority: P2
         Component: time
          Assignee: unassigned at sourceware dot org
          Reporter: fweimer at redhat dot com
  Target Milestone: ---

The daylight variable is supposed to be set to 1 if DST is every in use for the
current time zone. But __tzfile_read does this:

  __daylight = rule_stdoff != rule_dstoff;

This check can fail to set __daylight to 1 if the DST and non-DST offsets
happen to be the same.

The current tz data for Africa/Tripoli exposes this bug.

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[Bug time/29951] daylight variable not set correctly if last DST change coincides with offset change

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=29951

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fweimer at redhat dot com
           Assignee|unassigned at sourceware dot org   |fweimer at redhat dot com
              Flags|                            |security-
             Status|NEW                         |ASSIGNED

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[Bug time/29951] daylight variable not set correctly if last DST change coincides with offset change

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=29951

--- Comment #1 from Florian Weimer <fweimer at redhat dot com> ---
Patch posted:

[PATCH] time: Set daylight to 1 for matching DST/offset change (bug 29951)
<https://sourceware.org/pipermail/libc-alpha/2023-January/144434.html>

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[Bug time/29951] daylight variable not set correctly if last DST change coincides with offset change

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=29951

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
   Target Milestone|---                         |2.37
         Resolution|---                         |FIXED

--- Comment #2 from Florian Weimer <fweimer at redhat dot com> ---
Fixed via:

commit 35141f304e319109c322f797ae71c0b9420ccb05
Author: Florian Weimer <fweimer@redhat.com>
Date:   Thu Jan 5 18:21:25 2023 +0100

    time: Set daylight to 1 for matching DST/offset change (bug 29951)

    The daylight variable is supposed to be set to 1 if DST is ever in
    use for the current time zone.  But __tzfile_read used to do this:

      __daylight = rule_stdoff != rule_dstoff;

    This check can fail to set __daylight to 1 if the DST and non-DST
    offsets happen to be the same.

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