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

[Timofei Pushkin]

On Tue, 5 Aug 2025 06:55:02 GMT, Timofei Pushkin <tpushkin at openjdk.org> wrote:

>> test/jdk/jdk/crac/ignoreRestore/EngineFailureTest.java line 55:
>> 
>>> 53:             .startCheckpoint().waitForSuccess();
>>> 54: 
>>> 55:         new CracBuilder()
>> 
>> The `crexec` option for `CRaCEngine` is weird; looks like a leftover from times when we had `CREngineLibrary` as well. Is it supposed to execute CRIU, or completely fail the restore, leading to 'unavailable'?
>
> There is a long comment above explaining why this is done like this. Basically we need the failure to happen before `exec`ing the engine executable because there is no return to the parent VM from there.

If we had some library-based engine besides `crexec` I would use that

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PR Review Comment: https://git.openjdk.org/crac/pull/255#discussion_r2253343800