RFR: 8360025: (se) Convert kqueue Selector Implementation to use FFM APIs [v4]

[Per Minborg]

On Thu, 28 Aug 2025 15:02:57 GMT, Darragh Clarke <dclarke at openjdk.org> wrote:

>> Darragh Clarke has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 12 additional commits since the last revision:
>> 
>>  - fixed copyright header
>>  - merged master into branch
>>  - moved repeating code into own method
>>  - implementing feedback, adding missing errno checks, cleanup
>>  - feedback
>>  - general cleanup
>>  - small refactoring
>>  - Performance
>>  - implementing feedback
>>  - removed unrelated change
>>  - ... and 2 more: https://git.openjdk.org/jdk/compare/e5469821...cc5f558a
>
> Thanks for the thorough review, I'll address all these in the next commit.
> As for the changes to generated code, I'll draft up a list of what changed and why, though FFMUtils in particular came about as trying to move reusable utility methods into a shared place to cut down on code duplication going forward

> @DarraghClarke @minborg Would it be possible to provide a brief summary on what modifications have been done to the jextract-generated classes? The use of FFMUtils jumps out. Ideally they would be checked in without modification as it makes it easy to re-generate. It might be that this never happens but there is something a bit uncomfortable about checking in modified sources.

I think we could document the changes where we document how jextract is run. Ideally, we spoke about `sed` but maybe a more informal description can be made?

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PR Comment: https://git.openjdk.org/jdk/pull/25546#issuecomment-3244089693