[foreign-jextract] RFR: 8261906: Improve jextract support for virtual functions [v9]

[Jorn Vernee]

On Fri, 5 Mar 2021 18:10:27 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> This patch add support for function pointer calls. Whenever jextract encounters a function pointer variable (be it a global variable, or a struct field), it will additionally emit code to _call_ the function pointer - by means of a static wrapper around a virtual method handle.
>> 
>> The implementation is relatively straightforward, although there is some duplication in the code that is being emitted. I played with this a bit, to see if duplication could be removed, but I ended up with a single routine to generate wrappers which worked across the axis { virtual, non virtual } x { struct, global } - which in the end I found too complex for my taste (note that, e.g. when we're inside a struct, the logic to get the virtual address depends on what else is generated inside the struct, so there's a lot of ad-hocness).
>> 
>> For these reason I ended up with separate emit function for virtual wrappers (e.g. I did not reuse the code for native functions) - the code which emit virtual function wrappers is also overridden in StructBuilder. My sense is that if we move the code to use text blocks, the duplication will be much less problematic.
>> 
>> In OutputFactory, I cleaned up things a bit - since I realized that support for valist doesn't work - this is now removed. I will file a followup issue to add proper VaList support, both in downcalls and upcalls.
>
> Maurizio Cimadamore has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 13 commits:
> 
>  - Merge branch 'foreign-jextract' into virtual-calls
>  - Merge branch 'foreign-jextract' into virtual-calls
>  - * Make logic for resolving name of typedef of function pointer more robust
>    * Add more tests
>  - Add call to Utils.javaSafeIdentifier
>  - Replace direct function pointer accessor with functional interface getter
>  - Add restricted functional interface factory from address
>  - * removed unused #include in func.h
>    * add copyright headers in func.h/libFunc.h
>  - Consolidate code in OutputFactory to reuse FunctionInfo factory
>  - Add records to pass multiple information and simplify signatures of builders
>  - Remove Constant.MethodHandle from ConstantBuilder
>  - ... and 3 more: https://git.openjdk.java.net/panama-foreign/compare/2a85cbfd...73abb201

Looks good!

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Marked as reviewed by jvernee (Committer).

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