[crac] RFR: Fix CPUFeatures crash on new->old CPU [v5]

[Jan Kratochvil]

On Tue, 26 Mar 2024 16:05:45 GMT, Radim Vansa <rvansa at openjdk.org> wrote:

>> Jan Kratochvil has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Fix github compilation signedness problem
>
> Sorry for keeping this waiting for a long time. In the past I wasn't sure about using `/tmp/` rather than `shm_open` target but since `os::get_temp_directory()` has this part hard-coded, too, I think it's acceptable to use that one.
> 
> I would prefer `crac_restore_finalize` to use an enum rather than a `char` but otherwise this looks good - and if it fixes some usecase, let's integrate it.

@rvansa Sorry for the review but we have been last week talking with @AntonKozlov I should rather do the full rework (move the CPUFeatures protection to the parent JDK before the JDK is restored) than this fix-up.

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PR Comment: https://git.openjdk.org/crac/pull/134#issuecomment-2022205320