[lworld] RFR: 8373202: [lworld] ObjectReference.equals should follow == semantics for value objects [v4]

[Chris Plummer]

On Wed, 21 Jan 2026 04:31:41 GMT, Serguei Spitsyn <sspitsyn at openjdk.org> wrote:

>> Alex Menkov has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   space
>
> src/jdk.jdi/share/classes/com/sun/tools/jdi/ObjectReferenceImpl.java line 170:
> 
>> 168:                     throw exc.toJDIException();
>> 169:                 }
>> 170:             }
> 
> Nit: The lines 164, 177 can be simplified a little bit with move of the renamed `vm.canUseIsSameObject()` check equivalent to the `isValueClass()`.

If Valhalla is not supported on the target VM, there is no way for isValueClass() or isValueObject() to ever return true. If Valhalla is supported, they can return true, and we have to assume that JDWP and the debug agent support Valhalla also. We can't have Valhalla support in the JVM and not also have it in JDWP and the debug agent. The debugger/JDI will break if isValueObject() returns false for a value object.

> src/jdk.jdi/share/classes/com/sun/tools/jdi/VirtualMachineImpl.java line 841:
> 
>> 839:         return versionInfo().jdwpMajor >= 27;
>> 840:     }
>> 841: 
> 
> Nit: We may want to generalize this with something like 'maySupportValueClasses()'.

I'm not so sure this API is really even needed. I don't believe the current calls to it are valid.

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PR Review Comment: https://git.openjdk.org/valhalla/pull/1834#discussion_r2710939565
PR Review Comment: https://git.openjdk.org/valhalla/pull/1834#discussion_r2710942102