settimeofday breakage

[J William Piggott <elseifthen at gmx dot com>]

 > NEWS Version 2.31
 > Deprecated and removed features, and other changes affecting compatibility:
 >
 >   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).

I do not know who wrote this and my comment is not personal, but I
question the stated justification for this breakage.

The behavior of this function when called with two args has been in
place for nearly 30 years; I have never see a report of the kernel time
zone being set by 'accident'.

Then there is this recent comment:

 > Date: Thu, 6 Feb 2020 21:41:06 +0000
 > From: Joseph Myers <joseph@codesourcery.com>
 >
 > On Wed, 5 Feb 2020, Adhemerval Zanella wrote:
 >
 > > Once POSIX does remove the symbol, we can remove its definition from
 > > default visibility
 >
 > I don't see that being appropriate for a very long time.
 >

That was regarding gettimeofday, but should apply equally to
settimeofday.

I don't see how these two positions are reconciled:

 * get/settimeofday will be supported for the foreseeable future

 * settimeofday will be intentionally broken to prevent an 'accident'
   when using the 28 year old expected behavior.

Below is a table that I wrote for hwclock(8) to aid source readers in
understanding the block of code that follows it:

 *
 * +-------------------------------------------------------------------+
 * |                       settimeofday(tv, tz)                        |
 * |-------------------------------------------------------------------|
 * |     Arguments     |  System Time  | PCIL |           | warp_clock |
 * |   tv    |   tz    | set  | warped | set  | firsttime |   locked   |
 * |---------|---------|---------------|------|-----------|------------|
 * | pointer | NULL    |  yes |   no   |  no  |     1     |    no      |
 * | pointer | pointer |  yes |   no   |  no  |     0     |    yes     |
 * | NULL    | ptr2utc |  no  |   no   |  no  |     0     |    yes     |
 * | NULL    | pointer |  no  |   yes  |  yes |     0     |    yes     |
 * +-------------------------------------------------------------------+
 * ptr2utc: tz.tz_minuteswest is zero (UTC).
 * PCIL: persistent_clock_is_local, sets the "11 minute mode" timescale.
 * firsttime: locks the warp_clock function (initialized to 1 at boot).
 *

Note the unique behavior when called with two arguments which cannot be
easily reproduced.

What I used to accomplish in hwclock(8) with one call, now takes *three*!