RFR: JDK-8282798 java.lang.runtime.Carrier [v4]

[Maurizio Cimadamore]

On Thu, 10 Mar 2022 19:35:16 GMT, Jim Laskey <jlaskey at openjdk.org> wrote:

>> We propose to provide a runtime anonymous carrier class object generator; java.lang.runtime.Carrier. This generator class is designed to share anonymous classes when shapes are similar. For example, if several clients require objects containing two integer fields, then Carrier will ensure that each client generates carrier objects using the same underlying anonymous class. 
>> 
>> See JBS for details.
>
> Jim Laskey has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Leave public for the time being

src/java.base/share/classes/java/lang/runtime/Carrier.java line 346:

> 344:              * Carrier for longs and integers.
> 345:              */
> 346:             private final int[] integers;

I believe (@rose00 correct me if I'm wrong) that an `int[]` doesn't guarantee proper 64-but alignment of the first element in the array in 32-bit platforms. We ran into similar issues with the MemorySegment API, I believe. I think using a `long[]` if you want explicit 64-bit alignment is the safest choice.

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PR: https://git.openjdk.java.net/jdk/pull/7744