ModuleLayer.Controller strongly references Module

[Alan Bateman]

On 24/11/2021 12:19, Michał Kłeczek wrote:
> Hi Alan,
>
> (Disregard previous message - fat fingers)
>
> Attached is a first draft of the patch:
>
> 1. Controller is created upon ML construction and returned from static 
> ML.defineModules methods.
> 2. Created two controller liveness tests (they rely on System.gc() 
> though - not sure if there are some tricks to test it reliably).

I read your mail about "smart proxy" classes and lazy downloading of 
modules. I don't have an opinion at this time on whether this is worth 
doing or not.

If you want to experiment with patches then add a volatile field to ML 
and only set it when VM.isBooted() is true. In order words, let the 
ML.Controller for the boot layer be GC'ed as it is now (it would be 
attractive nuisance to keep it alive). There are many tests in the 
test/jdk tree that check that a weak ref is cleared, there is also some 
test infrastructure to help, so you might want to look at those.

-Alan