[lworld] RFR: 8373202: [lworld] ObjectReference.equals should follow == semantics for value objects

[Alex Menkov]

On Wed, 14 Jan 2026 04:16:31 GMT, Chris Plummer <cjplummer at openjdk.org> wrote:

>> Updated implementation of ObjectReference.equals and ObjectReference.hashCode to comply the spec for value objects.
>> Added the test for value object ctor debugging, the test verifies the behaviour is expected.
>> There is an issue with instance filter, it till be fixed separately (it's not yet clear how it would be better to fix it)
>> 
>> testing: tier1..4, hs-tier5-svc
>
> src/java.se/share/data/jdwp/jdwp.spec line 1804:
> 
>> 1802:         )
>> 1803:     )
>> 1804:     (Command IsSameObject=11
> 
> Are you going to add "preview API" warnings to these two APIs?

I'm not sure it makes much sense.
They are quite generic, I think about adding them to mainline in jdk 27 (but don't use by ObjectReferenceImpl.equals/hashCode)

> src/jdk.jdi/share/classes/com/sun/tools/jdi/ObjectReferenceImpl.java line 150:
> 
>> 148:     public boolean equals(Object obj) {
>> 149:         if (obj instanceof ObjectReferenceImpl other) {
>> 150:             if (!super.equals(obj)) { // checks if the references belong to the same VM
> 
> Have you considered adding a `this == obj` check at the beginning of this method. I think usually we are dealing with the same heap object, so this could be a quick check done for performance reasons.

If we decide to change this, it would be better to do it in mainline

> src/jdk.jdi/share/classes/com/sun/tools/jdi/ReferenceTypeImpl.java line 341:
> 
>> 339:         return ((modifiers & VMModifiers.IDENTITY) == 0)
>> 340:             && ((modifiers & VMModifiers.INTERFACE) == 0)
>> 341:             && ((modifiers & VMModifiers.ABSTRACT) == 0);
> 
> ReferenceTypeImpl has isXXX() apis to check these modifiers. We should probably use them here and add isIdentity().
> 
> It's unclear to me why you have to check INTERFACE and ABSTRACT. Isn't IDENTITY enough, or do interfaces and abstract classes not have the IDENTITY bit set?

value class can be abstract.

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PR Review Comment: https://git.openjdk.org/valhalla/pull/1834#discussion_r2692311793
PR Review Comment: https://git.openjdk.org/valhalla/pull/1834#discussion_r2692513236
PR Review Comment: https://git.openjdk.org/valhalla/pull/1834#discussion_r2692508079