RFR: 8356631: OopHandle replacement methods should not be called on empty handles

[Aleksey Shipilev]

On Tue, 13 May 2025 12:19:34 GMT, Erik Österlund <eosterlund at openjdk.org> wrote:

>> I noticed that in OopHandle/WeakHandle we have {replace,xchg,cmpxchg} methods that overwrite the handle. This is only safe to do when the handle is not empty -- i.e. when there is a storage allocated for it in relevant OopStorage. Otherwise we attempt the store to nullptr, and get a SEGV.
>> 
>> Only OopHandle::replace does the assertion for this. We need to add these asserts everywhere else.
>> 
>> Additional testing:
>>  - [x] Linux x86_64 server fastdebug, `all`
>
> Marked as reviewed by eosterlund (Reviewer).

Excellent, thanks @fisk.

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PR Comment: https://git.openjdk.org/jdk/pull/25139#issuecomment-2876369870