[tz] Wrong zdump output in timezone-2021e

[Paul Eggert]

On 1/25/22 02:57, Danilo Spinella via tz wrote:
> I consider this a bug due to the strange values printed by zdump.

Although the values look strange, they're valid boundary cases for 
ordinary zdump with 64-bit time_t. The difference in zdump output format 
was noted in the NEWS file entry for 2021b, which says "zdump -v now 
outputs more-useful boundary cases." So, for example, where 2021a "zdump 
-v Europe/Copenhagen" did not output the transition in the year 
2147485547 when localtime stops working, 2021b-through-2021e zdump 
outputs that transition.

To omit these extreme transitions you can use "zdump -V" instead of 
"zdump -v". There's also "zdump -i", which I use.

Now that you mention it, though, the 2021b-through-2021e zdump -v format 
is too cryptic for these these far-past or far-future transitions. I'm 
attaching the attached proposed patch that will cause "zdump -v 
Europe/Copenhagen" to output the following five lines for the last two 
transitions and the maximum time_t:

Europe/Copenhagen  Wed Dec 31 22:59:59 2147485547 UT = Wed Dec 31 
23:59:59 2147485547 CET isdst=0 gmtoff=3600
Europe/Copenhagen  Wed Dec 31 23:00:00 2147485547 UT = 67768036191673200 
(localtime failed)
Europe/Copenhagen  Wed Dec 31 23:59:59 2147485547 UT = 67768036191676799 
(localtime failed)
Europe/Copenhagen  67768036191676800 (gmtime failed) = 67768036191676800 
(localtime failed)
Europe/Copenhagen  9223372036854775807 (gmtime failed) = 
9223372036854775807 (localtime failed)


Compare to the 2021b-through-2021e output, which is harder to understand:

Europe/Copenhagen  Wed Dec 31 22:59:59 2147485547 UT = Wed Dec 31 
23:59:59 2147485547 CET isdst=0 gmtoff=3600
Europe/Copenhagen  Wed Dec 31 23:00:00 2147485547 UT = NULL
Europe/Copenhagen  Wed Dec 31 23:59:59 2147485547 UT = NULL
Europe/Copenhagen  67768036191676800 = NULL
Europe/Copenhagen  9223372036854775807 = NULL
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