Re: Update timezone to C99

[Peter Eisentraut]

On 14.11.25 22:11, Tom Lane wrote:
Peter Eisentraut <pe...@eisentraut.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.