RFR: 8338428: Print final VM flags for task [v4]

[Leonid Mesnik]

On Thu, 16 Jan 2025 06:12:01 GMT, Leonid Mesnik <lmesnik at openjdk.org> wrote:

>> Some VM flags might depend on the environment and it makes sense to log final flags so it is possible to get their value when investigating failures.
>> 
>> I added them to VMProps, so it is always dump final flags before running tests using "-XX:+PrintFlagsFinal".
>> 
>> Update:
>> There were intermittent compilation failures when I tried to use classes from testlibrary, so I rewrtite the code without them.
>
> Leonid Mesnik has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Added diagnostic flag

This invocation uses flags set to jtreg like -javaoption, -vmoption but not test-specific flags. 
Unfortunately, I don't have original request about this feature. As I understand the goal is to be able to check the specific vm flags that might be host specific for failed test run, like vector instructions, memory/GC ergonomics, etc. Might be make a diff with passed local run. I think that it is going to be used very rare, just if there are any question about VM default settings.

I think it is ok to have it in xml so far. The more problem is how people aware about this information. Probably add it to https://bugs.openjdk.org/browse/JDK-8346464

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PR Comment: https://git.openjdk.org/jdk/pull/23054#issuecomment-2596280821