From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
	id 529F93858D39; Wed, 10 Apr 2024 01:10:24 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 529F93858D39
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1712711424;
	bh=gueyt3G/vkhtrcdcLFSj0Rw6N5Nq92deF6oaIzZGegc=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=ntgRA9MePvGBJaEeBpyocC6SjjYvxcJKXncbXSmruVB7ff2ma8HyEG8fJBJ0sZ8Lm
	 Cy/s2Zb8J7cq3/0Nm18rN7dhv5ABksg0izCGqgw2DPFUrXC+WED+e7h6dSbTQeGxOV
	 M3kxiE175LbIGvUgWxa81hkE/MV5IgmTSDpWMuVM=
From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/114645] std::chrono::current_zone ignores $TZ on
 Linux
Date: Wed, 10 Apr 2024 01:10:23 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: libstdc++
X-Bugzilla-Version: 13.2.1
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: redi at gcc dot gnu.org
X-Bugzilla-Status: RESOLVED
X-Bugzilla-Resolution: WONTFIX
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-114645-4-9jzOl1VdOz@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-114645-4@http.gcc.gnu.org/bugzilla/>
References: <bug-114645-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
List-Id: <gcc-bugs.sourceware.org>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D114645

--- Comment #23 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Re https://github.com/cplusplus/draft/issues/6922

It can't possibly mean that the returned time zone *needs* to be the same as
the C library, because that's impossible in general, because the C library
isn't required to use IANA zones at all. See my TZ=3Dgarbage23nonsense exam=
ple.
There is no way to match that with std::chrono::time_zone without pointer
lifetime issues and inconsistencies like returning a time_zone that isn't in
the tzdb.

And if the C++ standard intended to require that TZ is respected on POSIX
systems, then it would say so. The absence of any requirement means it's not
required. TZ is not mentioned in the standard at all. The standard probably
isn't going to say it *must not* be used, because it's not in the business =
of
listing (or forbidding) possible vendor extensions. There might be systems
where a TZ environment var is the only way the time zone can be set, and it
always is an IANA zone. But I don't believe any of the targets libstdc++
supports fit into that category.=