RFR: 7903671: jcstress: Update buffer tests for JDK-8318966

[Aleksey Shipilev]

On Wed, 26 Feb 2025 17:50:28 GMT, Jiří Vaněk <jvanek at openjdk.org> wrote:

> part 1:  Detecting jdk of target VM and exuding illegible tests
> 
> This is prequel to full fixing of CODETOOLS-7903671. This PR detects target JDK version and then disables illegible tests.
> part 2 will be done in templates of affected tests and logic around generating the classes from them. In meantime this should server.
> 
> The jdk detection will be most likely used anyway. WDYT? If we agree on similar approach, I will create a new bug for this PR only.

Finally have time to look at this.

No, we are not going to hard-code test names in generic harness code. The common way to "skip" the test that are incompatible with some JDKs is to record them as "soft errors", which make them skipped. This is what [CODETOOLS-7903695](https://bugs.openjdk.org/browse/CODETOOLS-7903695) did, and it is supposed to be enough.

I think status quo with soft-failing alignment `8` tests, while inconvenient, is what we want. JDK 21 should be testing the heap buffers with strong alignment constraints. If anything, we should be looking whether to update the heap tests to _also_ include alignment `1`.

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PR Review: https://git.openjdk.org/jcstress/pull/159#pullrequestreview-2905202197