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[v3,1/2] timezone: handle truncated timezones from tzcode-2021d and later (BZ #28707)

Message ID 20211217203800.61364203B0@pchp3.se.axis.com
State Committed
Commit c36f64aa6dff13b12a1e03a185e75a50fa9f6a4c
Headers show
Series [v3,1/2] timezone: handle truncated timezones from tzcode-2021d and later (BZ #28707) | expand

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Context Check Description
dj/TryBot-apply_patch success Patch applied to master at the time it was sent

Commit Message

Hans-Peter Nilsson Dec. 17, 2021, 8:38 p.m. UTC
When using a timezone file with a truncated starting time,
generated by the zic in IANA tzcode-2021d a.k.a. tzlib-2021d
(also in tzlib-2021e; current as of this writing), glibc
asserts in __tzfile_read (on e.g. tzset() for this file) and
you may find lines matching "tzfile.c:435: __tzfile_read:
Assertion `num_types == 1' failed" in your syslog.

One example of such a file is the tzfile for Asuncion
generated by tzlib-2021e as follows, using the tzlib-2021e zic:
"zic -d DEST -r @1546300800 -L /dev/null -b slim
SOURCE/southamerica".  Note that in its type 2 header, it has
two entries in its "time-types" array (types), but only one
entry in its "transition types" array (type_idxs).

This is valid and expected already in the published RFC8536, and
not even frowned upon: "Local time for timestamps before the
first transition is specified by the first time type (time type
0)" ... "every nonzero local time type index SHOULD appear at
least once in the transition type array".  Note the "nonzero ...
index".  Until the 2021d zic, index 0 has been shared by the
first valid transition but with 2021d it's separate, set apart
as a placeholder and only "implicitly" indexed.  (A draft update
of the RFC mandates that the entry at index 0 is a placeholder
in this case, hence can no longer be shared.)

	* time/tzfile.c (__tzfile_read): Don't assert when no transitions
	are found.

Co-authored-by: Christopher Wong <Christopher.Wong@axis.com>
---
 time/tzfile.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
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Patch

diff --git a/time/tzfile.c b/time/tzfile.c
index 190a777152b3..8668392ad387 100644
--- a/time/tzfile.c
+++ b/time/tzfile.c
@@ -431,8 +431,8 @@  __tzfile_read (const char *file, size_t extra, char **extrap)
   if (__tzname[0] == NULL)
     {
       /* This should only happen if there are no transition rules.
-	 In this case there should be only one single type.  */
-      assert (num_types == 1);
+	 In this case there's usually only one single type, unless
+	 e.g. the data file has a truncated time-range.  */
       __tzname[0] = __tzstring (zone_names);
     }
   if (__tzname[1] == NULL)