[foreign-jextract] RFR: 8261906: Improve jextract support for virtual functions [v4]

[Jorn Vernee]

On Wed, 3 Mar 2021 13:59:35 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

> Having two is problematic in terms of adding the required overloads (e.g. we'd need to make up a new name for both options, which might be hard to decipher).

Ah right. Maybe we could call the direct accessor `f$call` instead ?
 
> It also occurs to me, that, with the currently implemented option, one could still do this:
> 
> ```
> func f = header::f;
> ```
> 
> E.g. if a functional interface is expected, it should be possible to instantiate it using a method reference.

That's an interesting idea, though I think it only works for global variables? (struct fields require a MemorySegment as well).

I think in general, when JDK-8259054 is implemented it should be easy enough to get a function interface instance:

func x = func.ofAddress(foo.f$get(segment));

So, maybe that's another reason to pick the simpler accessor...

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PR: https://git.openjdk.java.net/panama-foreign/pull/456