RFR: 8351565: Implement JEP 502: Stable Values (Preview) [v56]

[Jorn Vernee]

On Fri, 18 Apr 2025 13:19:05 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

>> Per Minborg has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Address comments on original vs underlying
>
> src/java.base/share/classes/java/lang/StableValue.java line 454:
> 
>> 452:      * @param content to set
>> 453:      * @throws IllegalStateException if this method is invoked directly by a supplier
>> 454:      *         provided to the {@link #orElseSet(Supplier)} method.
> 
> Why does this result in an exception? Given the example of dependent SV's I thought it would be fine or e.g. a stable value A to initialize another stable value B using `trySet`.

I see now the exception specification for `orElseSet`, I suggest saying something similar here:
Suggestion:

     * @throws IllegalStateException if a supplier invoked by {@link #orElseSet(Supplier)} recursively
     *         attempts to set this stable value by calling this method.

> src/java.base/share/classes/jdk/internal/lang/stable/StableValueImpl.java line 173:
> 
>> 171:     private void preventReentry() {
>> 172:         if (Thread.holdsLock(this)) {
>> 173:             throw new IllegalStateException("Recursive initialization is not supported");
> 
> Prevent users from having to look through the stack trace. Also, 'supported' sounds like it might be implemented later. I think 'allowed' is better to signal that this is an invariant.
> 
> Suggestion:
> 
>             throw new IllegalStateException("Recursive initialization of a StableValue is not allowed");

Or maybe a message like "Illegal recursive initialization of stable value".

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PR Review Comment: https://git.openjdk.org/jdk/pull/23972#discussion_r2050625500
PR Review Comment: https://git.openjdk.org/jdk/pull/23972#discussion_r2050761523