8288377: [REDO] DST not applying properly with zone id offset set with TZ env variable #9312

Deigue · 2022-06-28T18:52:32Z

This is a REDO of the Fix that was incompletely implemented earlier:
8285838: Fix for TZ environment variable DST rules

Offset calculation now accounts all the way upto year in order to avoid cross-day miscalculations as well as to calculate always in the correct direction for offset. In situations where there may be multiple days, the excess days of offset will be shaved off by applying mod to seconds_per_day , which will remove the excessive days that might be included in the offset calculation for special scenarios like a leap year / February months and variances between 30 and 31 days.

I have tested this solution with the cases where this fix had failed last time as well, and confirmed it works:
(where 7200 represents 7200 seconds -> +2 hour offset)
Sample output:

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JDK-8288377: [REDO] DST not applying properly with zone id offset set with TZ env variable

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Naoto Sato (@naotoj - Reviewer)

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8288377: Offset calculation fix for DST with custom TZ.

bridgekeeper · 2022-06-28T18:53:45Z

👋 Welcome back Deigue! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2022-06-28T18:56:59Z

@Deigue The following labels will be automatically applied to this pull request:

core-libs
i18n

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing lists. If you would like to change these labels, use the /label pull request command.

mlbridge · 2022-06-28T19:01:12Z

Webrevs

naotoj · 2022-06-28T22:15:39Z

I just wonder we could simply call strftime with %z conversion, rather than calculating the GMT offset ourselves. Would you like to try it out?

Deigue · 2022-06-29T14:35:02Z

@naotoj Thanks for letting me know, hadn't tried that function yet. At first look it seems to working exactly as needed, but I will need to parse the result into substrings to put a semi-colon between the hour and minute offset, in order to match the output required. But definitely looks much simpler in comparison ...

naotoj · 2022-06-29T15:54:19Z

I think you could simplify the code further, i.e. there will be no need to separate the function with #if defined(MACOSX). The code can be shared with all Unix platforms.

Deigue · 2022-06-30T18:29:42Z

I have simplified the implementation and tested that it works on Linux ... I still need to check this on a MAC OS computer and see if it working like before without any issues.

One more thing to note/I'd like to make sure is what the output looks like when TZ is GMT. Want to ensure that the final string being passed down is just "GMT" and that strftime invocation returns an empty result. If the result is coming out to be slightly different, then it could be a problem.

naotoj · 2022-06-30T20:05:05Z

src/java.base/unix/native/libjava/TimeZone_md.c

-}

-#else
+    strftime(offset, 6, "%z", &localtm);


Return value has to be examined. If it is not 5, then I'd expect falling back to "GMT".

Added check to verify output is as expected before proceeding, with fallback

naotoj · 2022-06-30T20:06:46Z

src/java.base/unix/native/libjava/TimeZone_md.c

-    }
-    sprintf(buf, (const char *)"GMT%c%02d:%02d",
-            sign, (int)(offset/3600), (int)((offset%3600)/60));
+    sprintf(buf, (const char *)"GMT%s", gmt_offset);


You could use the format string as "GMT%c%c%c:%c%c" so that the extra gmt_offset variable can be eliminated.

Adjusted, forgot that the final string returned was able to be formatted itself as well.

naotoj · 2022-06-30T20:12:35Z

One more thing to note/I'd like to make sure is what the output looks like when TZ is GMT. Want to ensure that the final string being passed down is just "GMT" and that strftime invocation returns an empty result. If the result is coming out to be slightly different, then it could be a problem.

You could compare GMT's hour/miute with localtime's. If they are identical, then return "GMT". For that, we may end up reviving #if defined (MACOSX) since macOS's tm struct has tm_gmtoff, but limited to that piece of code.

naotoj

Thanks. Looks good with one minor request.

naotoj · 2022-07-27T22:31:31Z

src/java.base/unix/native/libjava/TimeZone_md.c

-        offset = -offset;
-        sign = '+';
+    strftime(offset, 6, "%z", &localtm);
+    if (strlen(offset) != 5) {


What I meant was the return value from strftime, not the length from strlen, ie, if (strftime(...) != 5). It should be more robust.

naotoj

Looks good.

openjdk · 2022-07-29T18:18:36Z

@Deigue This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8288377: [REDO] DST not applying properly with zone id offset set with TZ env variable

Reviewed-by: naoto

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 1271 new commits pushed to the master branch:

af529be: 8285836: sun/net/www/http/KeepAliveCache/KeepAliveProperty.java failed with "RuntimeException: Failed in server"
b7d2bde: 8291733: Remove JFR events that expose hashtable
0971d34: Merge
54c093a: 8291524: jdk/jfr/event/runtime/TestClassLoaderStatsEvent.java Value not equal to 2, field='hiddenClassCount', value='0'
1d16c91: 8291512: Snippetize modules API examples
0ae8341: 8290908: misc tests fail: assert(!thread->owns_locks()) failed: must release all locks when leaving VM
5acf2d7: 8291578: Remove JMX related tests from ProblemList-svc-vthreads.txt
a6564d4: 8291650: Add delay to ClassUnloadEventTest before exiting to give time for JVM to send all events before VMDeath
af76c0c: 8291654: AArch64: assert from JDK-8287393 causes crashes
a9db5bb: 8291626: Remove Mutex::contains as it is unused
... and 1261 more: https://git.openjdk.org/jdk/compare/41de506ed6c9dc0331c2b6ae99c11623df05f34a...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

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Deigue · 2022-08-03T15:01:41Z

/integrate

openjdk · 2022-08-03T15:03:46Z

@Deigue
Your change (at version b09df3d) is now ready to be sponsored by a Committer.

naotoj · 2022-08-04T18:46:36Z

/sponsor

openjdk · 2022-08-04T18:49:18Z

Going to push as commit 3c32564.
Since your change was applied there have been 1295 commits pushed to the master branch:

fd9ac62: 8291457: Clean up lifecycle of CDS dump-time data structures
3ba3171: 8285935: Spurious lint warning for static method accessed through instance qualifier
92d2982: 8283232: x86: Improve vector broadcast operations
966ab21: 8291895: Remove PRAGMA_NONNULL_IGNORED from x86 and AArch64
aa557b9: 8288327: Executable.hasRealParameterData should not be volatile
d4a795d: 8283276: java/io/ObjectStreamClass/ObjectStreamClassCaching.java fails with various GCs
a3040fc: 8291360: Create entry points to expose low-level class file information
ce61eb6: 8290349: IP_DONTFRAGMENT doesn't set DF bit in IPv4 header
26e5c11: 4890041: Remove TAB and Shift TAB from Popup Menu in Motif Look & Feel
0bc804d: 8291762: Backout JDK-8291757 from jdk/jdk
... and 1285 more: https://git.openjdk.org/jdk/compare/41de506ed6c9dc0331c2b6ae99c11623df05f34a...master

Your commit was automatically rebased without conflicts.

openjdk · 2022-08-04T18:49:37Z

@naotoj @Deigue Pushed as commit 3c32564.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

8288377: Offset calculation fix for DST with custom TZ.

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8288377: Offset calculation fix for DST with custom TZ.

openjdk bot added the rfr Pull request is ready for review label Jun 28, 2022

openjdk bot added core-libs core-libs-dev@openjdk.org i18n i18n-dev@openjdk.org labels Jun 28, 2022

8288377: Simplified TZ offset calc and consolidate MACOS impl.

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naotoj reviewed Jun 30, 2022

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8288377: Added GMT0 corner case and minor format fixes.

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naotoj suggested changes Jul 27, 2022

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8288377: Adjusted length check for returned gmt-offset

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naotoj approved these changes Jul 29, 2022

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openjdk bot closed this Aug 4, 2022

openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review sponsor Pull request is ready to be sponsored labels Aug 4, 2022

8288377: [REDO] DST not applying properly with zone id offset set with TZ env variable #9312

8288377: [REDO] DST not applying properly with zone id offset set with TZ env variable #9312

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