[foreign-jextract] RFR: 8249810: Jextract should generate parameter types with Addressable type

[Henry Jen]

On Tue, 21 Jul 2020 21:38:14 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> src/jdk.incubator.jextract/share/classes/jdk/incubator/jextract/HeaderBuilder.java line 76:
>> 
>>> 75:             }
>>> 76:             if (sigtype.parameterType(i).equals(Addressable.class)) {
>>> 77:                 pExprs.add(pName + ".address()");
>> 
>> Here we assume the method handle have MemoryAddress type, while this is true in current implementation, it's possible
>> that mhtype actually have Addressable if caller chose to do so otherwise.
>
> No, that's not possible. The ABI does not support Addressable as a carrier type for parameter/returns. In other words,
> Addressable is a fiction that's only valid in jextract - it is not really taken into account by the guts of the ABI
> support.

It is true at ABI level, the method handle can only handle MemoryAddress. But there is nothing preventing something
like ConstantHelper to adapt the ABI-level MH to take Addressable as you do here.

What I am suggesting is simply saying you don't need add sigtype, simply take the incoming method type and adapt
MemoryAddress into Addressable.address().

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PR: https://git.openjdk.java.net/panama-foreign/pull/257