On Wed, 8 Jul 2026 07:13:38 GMT, David Simms <[email protected]> wrote:

>> This is a "*sub-review pull request*" for the first 
>> [preview](https://openjdk.org/jeps/12) of [JEP 401: Value Classes and 
>> Objects](https://openjdk.org/jeps/401), specifically 
>> [JDK-8317279](https://bugs.openjdk.org/browse/JDK-8317279): Standard library 
>> implementation of value classes and objects 
>> 
>>> [!NOTE]
>>> This pull request and the other sub-review pull requests listed below are 
>>> based on the "*master pull request*" 
>>> (https://github.com/openjdk/jdk/pull/31120). It contains the same full set 
>>> of code changes as the "*master pull request*" to preserve the full 
>>> implementation context; the language compiler, JVM, and standard library 
>>> changes are intertwined. This separate pull requests exist only to 
>>> subdivide the review and related discussion by area.
>> 
>> Other areas for review:
>> 
>> - [JDK-8317277](https://bugs.openjdk.org/browse/JDK-8317277): Java language 
>> implementation of value classes and objects
>>   - https://github.com/openjdk/jdk/pull/31121
>> - [JDK-8317278](https://bugs.openjdk.org/browse/JDK-8317278): JVM 
>> implementation of value classes and objects
>>   - https://github.com/openjdk/jdk/pull/31122
>> 
>> Code changes resulting from the review process should be made in 
>> [`valhalla/lworld`](https://github.com/openjdk/valhalla/).
>> 
>> `valhalla/lworld` is currently updated from `jdk/master` whenever a weekly 
>> [`jdk` tag](https://github.com/openjdk/jdk/tags) is created. At that time, 
>> code changes from `valhalla/lworld` will be propagated to the master pull 
>> request and to all sub-review pull requests, including this one.
>> 
>> Ultimately, review sign-off will be recorded on the "*master pull request*", 
>> and this pull request will be closed without integration.
>> 
>> This pull request has a large code surface area and often conflicts with 
>> `jdk/master` on a daily basis. Refer to 
>> [`valhalla/lworld`](https://github.com/openjdk/valhalla/) for the latest 
>> state of the project code, keeping in mind that it may lag several days 
>> behind `jdk/master`. Both repositories may be needed as references during 
>> review.
>> 
>> # PR implementation description
>> 
>> Here's a high-level overview of what's included here.
>> 
>> ### Core object behaviors
>> 
>> Introduced `Objects` methods to test for identity and `IdentityException` for
>> test failures; revised definitions of `==` and `identityHashCode` to work on 
>> the
>> fields of value objects.
>> 
>> - `src/java.base/share/classes/java/lang`
>> - `src/java.base/share/classes/java/util`
>> - `src/java.base/share/classes/java/lang/runtime`
>> - ...
>
> David Simms has updated the pull request incrementally with 11 additional 
> commits since the last revision:
> 
>  - Merge branch '8317277' into jep401_sub_review_8317279
>  - Merge remote-tracking branch 'valhalla/lworld' into 8317277
>  - 8387703: [lworld] address batch of comments in mainline PR
>    
>    Co-authored-by: Tobias Hartmann <[email protected]>
>    Reviewed-by: thartmann, dlong
>  - 8387661: [lworld] move generate_return_value_stub() to SharedRuntime
>    
>    Reviewed-by: adinn, thartmann
>  - 8387405: [lworld] is_always_flat_in_array should be always false
>    
>    Reviewed-by: thartmann
>  - 8387686: [lworld] Update the JNI specification version for value types
>    
>    Reviewed-by: alanb, dsimms
>  - 8387726: [lworld] JVMTI/JDWP/JDI docs cleanup
>    
>    Reviewed-by: sspitsyn, cjplummer
>  - 8387673: [lworld] C2: clone() intrinsic does not throw 
> CloneNotSupportedException for value classes not implementing Cloneable
>    
>    Reviewed-by: thartmann
>  - 8387709: [lworld] Split Valhalla tests from tier1_compiler_3 to avoid task 
> timeouts
>    
>    Reviewed-by: chagedorn
>  - 8387350: [lworld] ObjectOutputStream.writeObject() doesn't throw 
> InvalidClassException for Serializable instance with strict init fields
>    
>    Reviewed-by: alanb, jpai, thartmann
>  - ... and 1 more: https://git.openjdk.org/jdk/compare/8a7fdc6e...78d2bcdb

src/java.base/share/classes/java/lang/ref/SoftReference.java line 93:

> 91:      *
> 92:      * @param referent object the new soft reference will refer to
> 93:      * @throws IdentityException if the referent is not an

IIRC, there was discussion recently that at least some of the `java.lang.ref` 
classes accept `null` as a valid argument for the referent. If so, the "not an 
identity object" wording should be changed to "not an identity object or null" 
or similar.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/31123#discussion_r3560659427

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