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

[Alex Menkov]

On Wed, 14 Jan 2026 08:43:34 GMT, Serguei Spitsyn <sspitsyn at openjdk.org> wrote:

>> src/jdk.jdi/share/classes/com/sun/tools/jdi/ObjectReferenceImpl.java line 171:
>> 
>>> 169:     public int hashCode() {
>>> 170:         try {
>>> 171:             return JDWP.ObjectReference.ObjectHashCode.process(vm, this).hashCode;
>> 
>> Don't we want to limit the slow path to value objects?
>
>> We didn't do similar for Loom related APIs. I looked through the current canXXX list, and they all seem related to JVMTI capabilities, which don't apply to these two APIs. I think the expectation should be that the user checks the JDWP version to determine if it is implemented.
> 
> Yes, I remember about Loom. Asked this to be sure we are in sync. I agree with your suggestion.

> Don't we want to limit the slow path to value objects?

ok

>> src/jdk.jdi/share/classes/com/sun/tools/jdi/ReferenceTypeImpl.java line 334:
>> 
>>> 332: 
>>> 333:     // Inline type is a concrete value class.
>>> 334:     boolean isInlined() {
>> 
>> Why is this called isInlined()? Shouldn't it be isValueClass()? Do we want to expose it to users through ReferenceType? Should we also consider exposing a new isIdentity() API?
>
>> Why is this called isInlined()? Shouldn't it be isValueClass()?
> 
> I had the same question. The `isInlined()` matches the obsolete approach. The `isValueClass()` looks better.
> 
>> Do we want to expose it to users through ReferenceType?
> 
> If the JDI implementation needed it then there are some chances debuggers may need it as well. We have some time to decide. Preview allows to change the API specs in the future. I have a minor preference to expose it now. It is pretty simple and clear.
> 
>> Should we also consider exposing a new isIdentity() API?
> 
> It would be consistent with other modifier bits.

`isInlined` name (and its implementation) is consistent with hotspot code.
This API if required by ObjectReferenceImpl to determine if the reference is a value object (so the class cannot be abstract or interface).
To me `IsIdentity` (I think `isValue` is better) should be in `ClassType`, I'm updating ClassTypeImpl, it can be added to ClassType interface later if debuggers really need it).

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PR Review Comment: https://git.openjdk.org/valhalla/pull/1834#discussion_r2692339958
PR Review Comment: https://git.openjdk.org/valhalla/pull/1834#discussion_r2692365585