RFR: 8351565: Implement JEP 502: Stable Values (Preview) [v6]

[Chen Liang]

On Thu, 13 Mar 2025 15:22:43 GMT, Per Minborg <pminborg at openjdk.org> wrote:

>> Implement JEP 502.
>> 
>> The PR passes tier1-tier3 tests.
>
> Per Minborg has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 246 commits:
> 
>  - Merge branch 'master' into implement-jep502
>  - Clean up exception messages and fix comments
>  - Rename field
>  - Rename method and fix comment
>  - Rework reenterant logic
>  - Use acquire semantics for reading rather than volatile semantics
>  - Add missing null check
>  - Simplify handling of sentinel, wrap, and unwrap
>  - Fix JavaDoc issues
>  - Fix members in StableEnumFunction
>  - ... and 236 more: https://git.openjdk.org/jdk/compare/4e51a8c9...d6e1573f

src/java.base/share/classes/java/lang/StableValue.java line 56:

> 54:  * , {@linkplain #orElse(Object) orElse()}, or {@linkplain #orElseSet(Supplier) orElseSet()}.
> 55:  * <p>
> 56:  * A stable value that is <em>set</em> is treated as a constant by the JVM, enabling the

Before promoting the "constant" features, I would prefer more details about the transition to set - that setting is really a racy thing and only one actor succeeds in setting, and specify the memory effect (like the final field freeze) as a hb for the set and all subsequent gets that successfully observed that set.

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PR Review Comment: https://git.openjdk.org/jdk/pull/23972#discussion_r1997862275