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GNU C Library NEWS -- history of user-visible changes.
Version 2.31
Deprecated and removed features, and other changes affecting compatibility:
* The settimeofday function can still be used to set a system-wide time
zone when the operating system supports it. This is because the Linux
kernel reused the API, on some architectures, to describe a system-wide
time-zone-like offset between the software clock maintained by the kernel,
and the "RTC" clock that keeps time when the system is shut down.
However, to reduce the odds of this offset being set by accident,
settimeofday can no longer be used to set the time and the offset
simultaneously. If both of its two arguments are non-null, the call
will fail (setting errno to EINVAL).
Callers attempting to set this offset should also be prepared for the call
to fail and set errno to ENOSYS; this already happens on the Hurd and on
some Linux architectures. The Linux kernel maintainers are discussing a
more principled replacement for the reused API. After a replacement
becomes available, we will change settimeofday to fail with ENOSYS on all
platforms when its 'tzp' argument is not a null pointer.
settimeofday itself is obsolescent according to POSIX. Programs that set
the system time should use clock_settime and/or the adjtime family of
functions instead. We may cease to make settimeofday available to newly
linked binaries after there is a replacement for Linux's time-zone-like
offset API.
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hwclock(8) had one settimeofday(2) call where both args were set for
--hctosys when the RTC was ticking UTC. This allowed setting the system
time, timezone, and locking the warp_clock function with a single call.
That operation now takes 3 calls of settimeofday(2).
Although this common operation now takes three calls, the overall logic
for the set_system_clock() function was simplified.
Co-Author: Karel Zak <kzak@redhat.com>
Signed-off-by: J William Piggott <elseifthen@gmx.com>
Gbp-Pq: Name hwclock-make-glibc-2.31-compatible.patch
3c45559264