[lworld] RFR: 8354529: [lworld] Add tests for flat arrays in CDS archive [v2]

[Paul Hübner]

On Wed, 11 Feb 2026 22:16:02 GMT, Matias Saavedra Silva <matsaave at openjdk.org> wrote:

>> With CDS and AOT now fully supported in lworld, we need better test coverage to ensure that flat arrays are archived correctly. This patch adds a test to check that an array of both a migrate value class and a flattenable user defined value class can be archived and restored correctly in a static CDS dump. 
>> 
>> During the process it was discovered that the object subgraph was overlooking the element class of flat arrays, so proper handling was added courtesy of @iklam.
>> 
>> Verified with tier 1-5 tests.
>
> Matias Saavedra Silva has updated the pull request incrementally with one additional commit since the last revision:
> 
>   ioi comment and additional testing

Thanks for doing this. I've left a comment, if you think it is valid this is also something that can be addressed in a future RFE.

test/hotspot/jtreg/runtime/cds/appcds/cacheObject/ArchivedFlatArrayApp.java line 34:

> 32:     public static class ArchivedData {
> 33:         Integer[] intArray;
> 34:         CharPair[] charPairArray;

>From a high-level perspective, would it be valuable to additionally also test the following?
1. Null-free layouts, doesn't necessarily have to be 8 byte payloads, I think re-using `CharPair` and parameterizing the below test should be fine.
2. Scenarios where we flatten during archival but not at runtime or vice-versa (controlled by our flattening flag). I'm not sure if this would even work, but it feels like it'd be a good sanity test.

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PR Review: https://git.openjdk.org/valhalla/pull/2081#pullrequestreview-3790001081
PR Review Comment: https://git.openjdk.org/valhalla/pull/2081#discussion_r2797969322