8373668: Add override keyword to *Klass classes

[xmas92]

Using override provides better visibility and compiler support for suspicious virtual methods. It makes it clears when reading a class header file if a new virtual interface is introduced or if it simply overridden.

Testing

• GHA
• Running tier1 on Oracle supported platforms

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Progress

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Issue

• JDK-8373668: Add override keyword to *Klass classes (Enhancement - P4)

Reviewers

• Kim Barrett (@kimbarrett - Reviewer) Review applies to 00859dbd
• Thomas Schatzl (@tschatzl - Reviewer) Review applies to 00859dbd
• Julian Waters (@TheShermanTanker - Committer)
• David Holmes (@dholmes-ora - Reviewer)

Reviewing

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[openjdk]

@xmas92 This change now passes all automated pre-integration checks.

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

8373668: Add override keyword to *Klass classes

Reviewed-by: jwaters, dholmes, kbarrett, tschatzl

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At the time when this comment was updated there had been 12 new commits pushed to the master branch:

• 3f33eaa: 8373649: Convert simple AtomicAccess usage in ConcurrentHashTable to use Atomic
• 1748737: 8372988: Test runtime/Nestmates/membership/TestNestHostErrorWithMultiThread.java failed: Unexpected interrupt
• 317788f: 8360160: ubuntu-22-04 machine is failing client tests
• ... and 9 more: https://git.openjdk.org/jdk/compare/3559eeca0edd537c6160c6753cf6fc304afee4ca...master

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[mlbridge]

Webrevs

• 01: Full - Incremental (3b4009c8)
• 00: Full (00859dbd)

[kimbarrett]

Looks good.

A couple of pre-existing whitespace issues that you can fix or ignore.

I wonder if there would be any measurable benefit to using final instead in some
cases? But that should be looked at separately. It might be simpler to declare some
classes to be final.

[xmas92]

I wonder if there would be any measurable benefit to using final instead in some
cases? But that should be looked at separately. It might be simpler to declare some
classes to be final.

I know that I experimented with this at some point for the oop iterator. The result then was that it was not a reliable way to guarantee de-virtualisation. I also remember reading some blog post somewhere which explored different compilers and the benefits of final. I think it ultimately was not reliable enough to replace doing hand rolling things for where it matters, but got some improvements in some cases. However this was a few years ago so things might have improved.

Regardless of performance improvements, I think the final keyword makes the intended inheritance more clear and would be a worthwhile future RFE.

[TheShermanTanker]

+1 for use of helpful C++ features!

[dholmes-ora]

This all seems reasonable. I hope an IDE assisted with determining where override was needed, and virtual was not.

I think it would be good to see things marked final in the future as well.

[xmas92]

Thanks for the reviews. (Rebuilt with latest master merged locally.)
/integrate

[openjdk]

Going to push as commit 78c2d57.
Since your change was applied there have been 13 commits pushed to the master branch:

• b1e8c4e: 8372543: Shenandoah: undercalculated the available size when soft max takes effect
• 3f33eaa: 8373649: Convert simple AtomicAccess usage in ConcurrentHashTable to use Atomic
• 1748737: 8372988: Test runtime/Nestmates/membership/TestNestHostErrorWithMultiThread.java failed: Unexpected interrupt
• ... and 10 more: https://git.openjdk.org/jdk/compare/3559eeca0edd537c6160c6753cf6fc304afee4ca...master

Your commit was automatically rebased without conflicts.

[openjdk]

@xmas92 Pushed as commit 78c2d57.

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