Re: Update timezone to C99

On 14.11.25 22:11, Tom Lane wrote:
> Peter Eisentraut <peter(at)eisentraut(dot)org> writes:
>> On 12.11.25 19:02, Tom Lane wrote:
>>> Hm, I've had "re-sync TZ code with upstream" on my TODO list for
>>> several years now. I believe there's been quite a bit of churn
>>> upstream since tzcode2020d, some of it oriented towards this same
>>> issue of code modernization. Maybe we should try to sync with
>>> a newer release while we're at it.
>
>> My idea was to do this C99 adjustment first so that the differences to
>> upstream are reduced, which would hopefully simplify updating to that
>> newer code.
>
> Fair enough. I looked through the patch briefly and had a couple of
> minor quibbles:
>
> @@ -905,7 +906,7 @@ transtime(const int year, const struct rule *const rulep,
> for (i = 1; i < rulep->r_week; ++i)
> {
> if (d + DAYSPERWEEK >=
> - mon_lengths[(int) leapyear][rulep->r_mon - 1])
> + mon_lengths[leapyear][rulep->r_mon - 1])
> break;
> d += DAYSPERWEEK;
> }
> @@ -915,7 +916,7 @@ transtime(const int year, const struct rule *const rulep,
> */
> value = d * SECSPERDAY;
> for (i = 0; i < rulep->r_mon - 1; ++i)
> - value += mon_lengths[(int) leapyear][i] * SECSPERDAY;
> + value += mon_lengths[leapyear][i] * SECSPERDAY;
> break;
> }
>
> "leapyear" is bool, and I believe these casts-to-int were put in to
> suppress compiler bleats about up-casting that to int. This probably
> dates from when we equated bool to char, and maybe it's moot now,
> but I'm not sure.

Correct, with bool as char this would have fallen afoul of
-Wchar-subscripts, which is included in -Wall.

I could remove these casts as a separate patch so that the reason can be
documented more clearly.

> @@ -47,12 +49,15 @@ typedef int64 zic_t;
> static ptrdiff_t const PTRDIFF_MAX = MAXVAL(ptrdiff_t, TYPE_BIT(ptrdiff_t));
> #endif
>
> -/*
> - * The type for line numbers. In Postgres, use %d to format them; upstream
> - * uses PRIdMAX but we prefer not to rely on that, not least because it
> - * results in platform-dependent strings to be translated.
> - */
> -typedef int lineno_t;
> +/* The minimum alignment of a type, for pre-C11 platforms. */
> +#if __STDC_VERSION__ < 201112
> +#define _Alignof(type) offsetof(struct { char a; type b; }, b)
> +#endif
>
> Since we've dropped pre-C11 support, I wonder why we'd include this
> upstream workaround for that.

I figured it would be better to reduce divergences from upstream, even
if we don't need all the code.