Improve port to NetBSD tzalloc

Problem reported by Valery Ushakov (Bug#30738#13).
* src/editfns.c (tzlookup) [__NetBSD_Version__ < 700000000]:
If tzalloc fails for any reason other than memory exhaustion,
assume it’s because NetBSD 6 does not support tzalloc on
POSIX-format TZ strings, and fall back on tzdb if possible.

1 files changed, 12 insertions, 0 deletions

diff --git a/src/editfns.c b/src/editfns.c
index 6ecc83fc302..d26319441b3 100644
--- a/src/editfns.c
+++ b/src/editfns.c
@@ -204,6 +204,18 @@ tzlookup (Lisp_Object zone, bool settz)
         invalid_time_zone_specification (zone);
 
       new_tz = tzalloc (zone_string);
+
+#if defined __NetBSD_Version__ && __NetBSD_Version__ < 700000000
+      /* NetBSD 6 tzalloc mishandles POSIX TZ strings (Bug#30738).
+         If possible, fall back on tzdb.  */
+      if (!new_tz && errno != ENOMEM && plain_integer
+          && XINT (zone) % (60 * 60) == 0)
+        {
+          sprintf (tzbuf, "Etc/GMT%+"pI"d", - (XINT (zone) / (60 * 60)));
+          new_tz = tzalloc (zone_string);
+        }
+#endif
+
       if (!new_tz)
         {
           if (errno == ENOMEM)