[crac] RFR: 8364538: [CRaC] Test CRaCIgnoreRestoreIfUnavailable [v2]

[Timofei Pushkin]

On Tue, 5 Aug 2025 12:44:11 GMT, Radim Vansa <rvansa at openjdk.org> wrote:

>> Added  `NoCPUFeaturesTest`
>
> I was not implying that you should add the test for missing CPU features, but good to have one.
> 
> My point is that running `simengine` alone should be a no-op (yes, you're testing that simengine works, but that's not a point of this test). The comment says `Create an empty image` but simengine is not supposed to create an empty image, it is not supposed to do anything. As a side-effect, JVM creates the directory.
> 
> My understanding is that you are doing that to prevent checks before entering the engine to fail in a different manner than the test is supposed to do. I consider running the test with two different engines a confusing, obscure way to get the prerequisites; you could just `mkdir` and write a dummy CPU features file.

Writing a dummy CPU features file would make the test depend on the format of the file, i.e. both on crexec and CPU features implementation.

The only way I see to make the test less artificial is to create a library-based simengine.

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PR Review Comment: https://git.openjdk.org/crac/pull/255#discussion_r2254312962