touch -t fails on Linux if machine has timezone GMT

[barnex]

cargo test currently fails on my Debian and my Ubuntu 21.04 machine, both of which have timezone GMT (UTC+0).

---- test_du::test_du_time stdout ----
current_directory_resolved: 
run: /<redacted>/src/coreutils/target/debug/coreutils touch -a -t 201505150000 date_test
thread 'test_du::test_du_time' panicked at 'Command was expected to succeed.
stdout = 
 stderr = touch: invalid date format '201505150000'
', tests/common/util.rs:174:9

Actually cargo run touch -a -t xxxxxxxxxx file fails for any valid timestamp, irrespective of it being near daylight saving time changes or not.

When I change my timezone to anything other than GMT, the issue disappears.

I suspect this issue may be related to handling of daylight saving time, introduced in 85a7375#diff-9565d8fad7b29837b3b468a61a809dc187fb351a72421ffe4b7c4879a8445b27R279.

Adding debug statements for that code shows, for the failing test case:

tm = { 
  tm_sec: 0, tm_min: 0, 
  tm_hour: 0, 
  tm_mday: 15, tm_mon: 4, tm_year: 115, tm_wday: 0, tm_yday: 0, tm_isdst: 0, 
  tm_utcoff: 0, 
  tm_nsec: 0 
},

tm2 = Tm {
  tm_sec: 0, tm_min: 0, 
  tm_hour: 1, 
  tm_mday: 15, tm_mon: 4, tm_year: 115, tm_wday: 5, tm_yday: 134, tm_isdst: 0,
  tm_utcoff: 3600, 
  tm_nsec: 0
}

Note the difference in tm_utcoff between the two, which appears to be the cause of this issue: even though the two times are equivalent, they have a different tm_hour, causing them to be interpreted as different and therefore invalid.

[sylvestre]

@barnex do you want to propose a fix?
thanks

[barnex]

Sure, happy to look into this.

[sylvestre]

@barnex ping?

[barnex]

When I update the time comparison to take UTC offsets into account, the test in question passes, but then other tests fail because we now accept some timestamps that GNU rejects. I'm afraid that I'll have to hand off this issue at this point. Perhaps @ajanicij who wrote the initial timestamp checks is better placed to look into this.

[ajanicij]

I will look into it.

[qua3k]

Hi, wanted to look at this recently and it seems to pass the tests, can this be closed?

[ajanicij]

Sorry I haven't had time to look into it. It's good news that it is passing. @qua3k In which timezone did you try it?

[qua3k]

This was with GMT (temporarily symlinked /etc/localtime to the appropriate file on Ubuntu 22.04)