RFR: 8302154: Hidden classes created by LambdaMetaFactory can't be unloaded [v2]

[Ioi Lam]

On Tue, 21 Feb 2023 18:39:31 GMT, Volker Simonis <simonis at openjdk.org> wrote:

>> Volker Simonis has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - Remove assertions which insist on Lambda proxy classes being strongly linked to their class loader
>>  - Removed unused import of STRONG und updated copyright year
>
> I hear your arguments although I don't agree :)
> 
> Can we at least get consensus on that the current design to create a new ClassLoaderData for each non-strongly linked Hidden Class just in order to enable simple unloading isn't the greatest design and should eventually be replaced by a more sophisticated implementation which allows non-strongly linked Hidden Classes to share a single ClassLoaderData but still enable unloading for them once they aren't referenced any more?

@simonis I want to ask a basic question -- what is the reason for your code to call `LambdaMetafactory.metafactory()` directly? It looks like you want to implement so sort of dynamic dispatch. Can equivalent functionality be implemented by the app itself?

If there's a real need for such a style of programming, and it requires some sort of built-in support in by the JDK, maybe we should have a proper API instead of piggy-backing on `LambdaMetafactory.metafactory()`.

I think if you give us more background, we can make this a more productive discussion than focusing on "did we make the right decision N versions ago" without defining what "right" means :-)

I would suggest re-booting this decision in the mailing lists rather than continuing in this PR.

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PR: https://git.openjdk.org/jdk/pull/12493