[tz] [PROPOSED 2/5] zic no longer generates utoff == -2**31

[Paul Eggert via tz]

This rejects outlandish zic input like "Zone X -596523:14:08 - XXT".
* NEWS: Mention this.
* zic.c (addtype): Do not allow a UT offset of -2**31.
---
 NEWS  | 2 ++
 zic.c | 3 ++-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/NEWS b/NEWS
index f645aafa..b4f3ead8 100644
--- a/NEWS
+++ b/NEWS
@@ -26,6 +26,8 @@ Unreleased, experimental changes
     zic no longer assumes you can fflush a read-only stream.
     (Problem reported by Christos Zoulas.)
 
+    zic no longer generates UT offsets equal to -2**31, as RFC 9636
+    prohibits them.
 
 Release 2025c - 2025-12-10 14:42:37 -0800
 
diff --git a/zic.c b/zic.c
index eecd8ac2..b69414dd 100644
--- a/zic.c
+++ b/zic.c
@@ -3760,7 +3760,8 @@ addtype(zic_t utoff, char const *abbr, bool isdst, bool 
ttisstd, bool ttisut)
 {
        register int    i, j;
 
-       if (! (-1 - 2147483647 <= utoff && utoff <= 2147483647)) {
+       /* RFC 9636 section 3.2 specifies this range for utoff.  */
+       if (! (-2147483647 <= utoff && utoff <= 2147483647)) {
                error(_("UT offset out of range"));
                exit(EXIT_FAILURE);
        }
-- 
2.51.0