RFR: JDK-8282798 java.lang.runtime.Carrier

[Brian Goetz]

You keep saying “what we need”.  But really, what I think you mean is “what the scheme I have in mind needs.”  Can we try and separate these out?  I don’t think any of these are *needed*, but maybe you want to make the argument that you have a better scheme in mind, and we should choose that scheme, and therefore then we might need them.  

> On Mar 8, 2022, at 10:04 AM, Remi Forax <forax at univ-mlv.fr> wrote:
> 
> Hi Jim,
> I believe that there is a mismatch about what is needed for the pattern matching and the API you propose.
> The Carrier API allows to map one tuple of types to one storage representation based on ints, longs and references.
> 
> But what we need is to have several shapes for the same storage, mapping is not one to one but many to one, more like how unions are mapped in C.
> For a switch, if we have several cases, each one need it's own shape to store the bindings but at the same time we also need one field to be the same for all shapes (the field of type int indicating which case match) so one storage but many shapes.
> 
> Rémi
> 
> ----- Original Message -----
>> From: "Jim Laskey" <jlaskey at openjdk.java.net>
>> To: "core-libs-dev" <core-libs-dev at openjdk.java.net>
>> Sent: Tuesday, March 8, 2022 3:11:39 PM
>> Subject: RFR: JDK-8282798 java.lang.runtime.Carrier
> 
>> 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.
>> 
>> -------------
>> 
>> Commit messages:
>> - Introduce java.lang.runtime.Carrier
>> 
>> Changes: https://git.openjdk.java.net/jdk/pull/7744/files
>> Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7744&range=00
>> Issue: https://bugs.openjdk.java.net/browse/JDK-8282798
>> Stats: 1085 lines in 2 files changed: 1085 ins; 0 del; 0 mod
>> Patch: https://git.openjdk.java.net/jdk/pull/7744.diff
>> Fetch: git fetch https://git.openjdk.java.net/jdk pull/7744/head:pull/7744
>> 
>> PR: https://git.openjdk.java.net/jdk/pull/7744