[tz] [PROPOSED] zic -r is incompatible with rolling leaps

[Arthur David Olson]

Rolling leap seconds were meant to accommodate the New York Times Square
ball drop; at least in some leap-second years, there'd be a
"3...2...1...leap...Happy New Year" countdown, placing the leap second at
midnight New York time rather than midnight London time.

    @dashdashado


On Sun, Sep 12, 2021 at 9:43 PM Paul Eggert via tz <tz at iana.org> wrote:

> * NEWS, zic.8: Mention this.
> * zic.c (leapadd): Report an error if the user tries it.
> ---
>  NEWS  | 3 +++
>  zic.8 | 3 +++
>  zic.c | 4 ++++
>  3 files changed, 10 insertions(+)
>
> diff --git a/NEWS b/NEWS
> index 1b5535a..62a7ba2 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -137,6 +137,9 @@ Unreleased, experimental changes
>      last time transition disagreed with the TZ string, contrary to
>      Internet RFC 8563 section 3.3.
>
> +    zic -r now reports an error if given rolling leap seconds, as this
> +    usage has never generally worked and is evidently unused.
> +
>      zic now generates a POSIX-conforming TZ string for TZif files
>      where all-year DST is predicted for the indefinite future.
>      For example, for all-year Eastern Daylight Time, zic now generates
> diff --git a/zic.8 b/zic.8
> index b77841b..3023ebe 100644
> --- a/zic.8
> +++ b/zic.8
> @@ -709,6 +709,9 @@ or
>  .q "Rolling"
>  if the leap second time given by the other fields should be interpreted as
>  local (wall clock) time.
> +(Rolling leap seconds are not supported if the
> +.B \*-r
> +option is used.)
>  .PP
>  The expiration line, if present, has the form:
>  .nf
> diff --git a/zic.c b/zic.c
> index e2a7e13..b06ef66 100644
> --- a/zic.c
> +++ b/zic.c
> @@ -3144,6 +3144,10 @@ leapadd(zic_t t, int correction, int rolling)
>                 error(_("too many leap seconds"));
>                 exit(EXIT_FAILURE);
>         }
> +       if (rolling && (lo_time != min_time || hi_time != max_time)) {
> +         error(_("Rolling leap seconds not supported with -r"));
> +         exit(EXIT_FAILURE);
> +       }
>         for (i = 0; i < leapcnt; ++i)
>                 if (t <= trans[i])
>                         break;
> --
> 2.30.2
>
>
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