From: Rich Felker <dalias@libc.org>
To: libc-alpha@sourceware.org
Subject: Re: [RFC v4 07/24] time: Deprecate struct timezone members
Date: Sun, 11 Aug 2019 17:28:00 -0000 [thread overview]
Message-ID: <20190811172829.GN9017@brightrain.aerifal.cx> (raw)
In-Reply-To: <875zn3yfki.fsf@oldenburg2.str.redhat.com>
On Sun, Aug 11, 2019 at 03:52:45PM +0200, Florian Weimer wrote:
> * Alistair Francis:
>
> > On Fri, Aug 9, 2019 at 6:20 PM Paul Eggert <eggert@cs.ucla.edu> wrote:
> >>
> >> Alistair Francis wrote:
> >> > - int tz_minuteswest; /* Minutes west of GMT. */
> >> > - int tz_dsttime; /* Nonzero if DST is ever in effect. */
> >> > + int tz_minuteswest_dep; /* Minutes west of GMT. */
> >> > + int tz_dsttime_dep; /* Nonzero if DST is ever in effect. */
> >> These two members should be declared with __attribute_deprecated__. And once we
> >> do that, do we still need to change their names? I don't recall any other
> >> instance of such name-changing.
> >
> > The name changing is coming from a suggestion here [1]. I do find it a
> > little aggressive though as I do see some build failures, specifically
> > for systemd.
>
> Good point. systemd does this:
>
> tz.tz_minuteswest = -minutesdelta;
> tz.tz_dsttime = 0; /* DST_NONE */
>
> /*
> * If the RTC does not run in UTC but in local time, the very first
> * call to settimeofday() will set the kernel's timezone and will warp the
> * system clock, so that it runs in UTC instead of the local time we
> * have read from the RTC.
> */
> if (settimeofday(tv_null, &tz) < 0)
> return negative_errno();
>
> It seems to me that struct timezone is not actually deprecated on the
> kernel side when used with settimeofday. This would be something which
> has to happen before we can change its definition.
The only effect I'm aware of it ever having had on the kernel side was
actively harmful: applying the offset to the timestamps of all files
on fatfs mounts. This has all kinds of consistency problems with DST,
timezone changes, etc. and is lossy/destructive of data. Back in 2005
I recall writing a script to do a best-case repair on digital camera
timestamps (correctly recorded on the fatfs in UTC) that Linux mangled
via moving them to hdd under several different local timezones.
systemd should not be doing this at all. If anyone wants this feature
it should be a mount option tzoff=..., not a global that's secretly
set to match your system tz.
Rich
next prev parent reply other threads:[~2019-08-11 17:28 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-10 1:03 [RFC v4 00/24] RISC-V glibc port for the 32-bit Alistair Francis
2019-08-10 1:03 ` [RFC v4 13/24] RISC-V: Use 64-bit timespec in clock_gettime vdso calls Alistair Francis
2019-08-10 1:03 ` [RFC v4 04/24] sysdeps/wait: Use waitid if avaliable Alistair Francis
2019-08-10 1:03 ` [RFC v4 02/24] sysdeps/nanosleep: Use clock_nanosleep_time64 " Alistair Francis
2019-08-12 17:22 ` Joseph Myers
2019-08-14 18:24 ` Alistair Francis
2019-08-14 20:15 ` Joseph Myers
2019-08-14 21:39 ` Stepan Golosunov
2019-08-10 1:03 ` [RFC v4 12/24] RISC-V: define __NR_* as __NR_*_time64/64 for 32-bit Alistair Francis
2019-08-10 1:03 ` [RFC v4 05/24] sysdeps/clock_gettime: Use clock_gettime64 if avaliable Alistair Francis
2019-08-12 19:46 ` Joseph Myers
2019-08-13 23:48 ` Alistair Francis
2019-08-14 16:37 ` Joseph Myers
2019-08-14 18:12 ` Alistair Francis
2019-08-10 1:03 ` [RFC v4 16/24] RISC-V: The ABI implementation for the 32-bit Alistair Francis
2019-08-10 1:03 ` [RFC v4 01/24] sunrpc/clnt_udp: Ensure total_deadline is initalised Alistair Francis
2019-08-10 1:03 ` [RFC v4 09/24] Documentation for the RISC-V 32-bit port Alistair Francis
2019-08-12 20:02 ` Joseph Myers
2019-08-10 1:03 ` [RFC v4 17/24] RISC-V: Hard float support for the 32 bit Alistair Francis
2019-08-10 1:03 ` [RFC v4 10/24] RISC-V: Use 64-bit time_t and off_t for RV32 and RV64 Alistair Francis
2019-08-10 1:03 ` [RFC v4 15/24] RISC-V: Add path of library directories for RV32 Alistair Francis
2019-08-10 1:03 ` [RFC v4 06/24] sysdeps/timespec_get: Use clock_gettime64 if avaliable Alistair Francis
2019-08-12 19:46 ` Joseph Myers
2019-08-15 18:03 ` Alistair Francis
2019-08-15 19:46 ` Joseph Myers
2019-08-15 20:52 ` Alistair Francis
2019-08-15 20:59 ` Joseph Myers
2019-08-15 21:16 ` Alistair Francis
2019-08-15 21:19 ` Joseph Myers
2019-08-15 21:23 ` Alistair Francis
2019-08-15 21:28 ` Joseph Myers
2019-08-15 21:35 ` Alistair Francis
2019-08-10 1:03 ` [RFC v4 08/24] sysdeps/stat: Copy the statx struct to stat instead of stat64 Alistair Francis
2019-08-12 20:01 ` Joseph Myers
2019-08-12 22:26 ` Alistair Francis
2019-08-12 23:02 ` Joseph Myers
2019-08-12 23:10 ` Alistair Francis
2019-08-12 23:31 ` Joseph Myers
2019-08-13 20:40 ` Alistair Francis
2019-08-10 1:03 ` [RFC v4 07/24] time: Deprecate struct timezone members Alistair Francis
2019-08-10 1:20 ` Paul Eggert
2019-08-10 1:30 ` Alistair Francis
2019-08-11 13:52 ` Florian Weimer
2019-08-11 16:59 ` Alistair Francis
2019-08-11 17:28 ` Rich Felker [this message]
2019-08-12 8:22 ` Florian Weimer
2019-08-12 15:42 ` Zack Weinberg
2019-08-12 20:20 ` Joseph Myers
2019-08-12 21:08 ` Zack Weinberg
2019-08-12 21:26 ` Joseph Myers
2019-08-12 22:13 ` Alistair Francis
2019-08-12 23:16 ` Zack Weinberg
2019-08-13 0:53 ` Paul Eggert
2019-08-13 1:04 ` Zack Weinberg
2019-08-12 22:11 ` Alistair Francis
2019-08-10 1:03 ` [RFC v4 03/24] sysdeps/gettimeofday: Use clock_gettime64 if avaliable Alistair Francis
2019-08-12 17:27 ` Joseph Myers
2019-08-10 1:04 ` [RFC v4 14/24] RISC-V: Support dynamic loader for the 32-bit Alistair Francis
2019-08-10 1:04 ` [RFC v4 11/24] RISC-V: define __NR_futex as __NR_futex_time64 for 32-bit Alistair Francis
2019-08-10 1:04 ` [RFC v4 23/24] WIP: syscall.list: Call 64-bit versions of syscalls Alistair Francis
2019-08-14 18:39 ` Alistair Francis
2019-08-14 18:57 ` Florian Weimer
2019-08-15 21:43 ` Alistair Francis
2019-08-19 11:30 ` Florian Weimer
2019-08-10 1:04 ` [RFC v4 19/24] RISC-V: Build Infastructure for the 32-bit Alistair Francis
2019-08-10 1:04 ` [RFC v4 18/24] RISC-V: Add ABI lists Alistair Francis
2019-08-10 1:04 ` [RFC v4 22/24] RISC-V: Use 64-bit vdso syscalls for RV32 Alistair Francis
2019-08-10 1:04 ` [RFC v4 20/24] RISC-V: Fix llrint and llround missing exceptions on RV32 Alistair Francis
2019-08-10 1:04 ` [RFC v4 21/24] Add RISC-V 32-bit target to build-many-glibcs.py Alistair Francis
2019-08-10 1:04 ` [RFC v4 24/24] timerfd_settime: Use 64-bit call if avaliable Alistair Francis
2019-08-10 1:28 ` Alistair Francis
2019-08-20 20:11 ` Maciej W. Rozycki
2019-08-12 20:09 ` Joseph Myers
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