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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/109857] Debian stable's tzdata 2021a has bad data
 that cannot be parsed by libstdc++
Date: Tue, 16 May 2023 11:59:22 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109857

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #4)
> This would be bad in the Debian case, because they backport changes to the
> DST rules from the upstream IANA database, but for Debian stable don't
> change the "version" string in tzdata.zi. This means libstdc++ will always
> think the system tzdata.zi version "2021a" is older than the bundled
> "2023c", even though the system file might actually have newer rules
> backported from upstream. If we automatically used the bundled 2023c data=
 we
> would actually be using older data.

Another consequence of the Debian stable policy is that a long-running C++
process will think it always has the latest tzdb, even if the on-disk tzdat=
a.zi
has actually been updated by apt-get. i.e. std::chrono::reload_tzdb() will
never do anything.

Maybe I should report this as a bug to Debian, and ask them to append some
discriminator to the version string, like "2021a.1", "2021a.2" etc.=