[lworld] RFR: 8368274: [lworld] Unsafe.compareAndExchangeFlatValue() wrongly assumes padding bytes are the same for identical value objects [v5]

[Daniel D. Daugherty]

On Thu, 22 Jan 2026 18:48:41 GMT, Chen Liang <liach at openjdk.org> wrote:

>> Use the raw value get as witness, because the flat value get may ignore garbage value and cause infinite loop as a result. Waiting for a test case.
>
> Chen Liang has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 10 commits:
> 
>  - Merge branch 'lworld' into fix/unsafe-flat-cas
>  - Comment update
>  - Merge branch 'lworld' of https://github.com/openjdk/valhalla into fix/unsafe-flat-cas
>  - Remove test as permitted
>  - Fixes, VHTMHAV now passes
>  - Merge branch 'lworld' of https://github.com/openjdk/valhalla into fix/unsafe-flat-cas
>  - A test
>  - Merge branch 'lworld' of https://github.com/openjdk/valhalla into fix/unsafe-flat-cas
>  - Merge branch 'lworld' of https://github.com/openjdk/valhalla into fix/unsafe-flat-cas
>  - Attempt to fix garbage cas

test/jdk/ProblemList.txt line 799:

> 797: # valhalla
> 798: build/CheckFiles.java 8376088  generic-all
> 799: java/lang/invoke/VarHandles/VarHandleTestMethodHandleAccessValue.java 8367346 generic-all

This PR's bugID is 8368274 while the ProblemList entry's bugID is 8367346.
It looks like JDK-8367346 is closed as a duplicate of JDK-8368274 so all the
accounting is good here, but I wanted to document what we've done.

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PR Review Comment: https://git.openjdk.org/valhalla/pull/1734#discussion_r2718882661