notes on binding C++

[Samuel Audet]

On 02/05/2018 06:10 AM, Maurizio Cimadamore wrote:
> On 04/02/18 02:38, Samuel Audet wrote:
>> The only thing that you have been able to show me until now requires
>>
>> Java -> C wrappers -> C++
>>
>> For C++ libraries, that gains us nothing over JNI! Except that now we 
>> have 2 ways of accessing native libraries that have very different 
>> APIs. Not so great for usability, but that is OK, in a way. 
> Going from Java to C wrappers is not the same of going from Java to JNI. 
> That's the whole point. The wrappers are Panama-friendly C-like entry 
> points, so we can jump straight from Java to the native wrapper entry 
> point w/o any overhead (if the foundations are laid well enough, that is).
> 
> Moreover, if we leave enough breadcrumbs around, the JIT might 
> understand that 'this is a wrapper around a C++ inlined function' (after 
> all there's only a limited amount of wrappers needed for C++ interop) 
> and optimize that  suitably. This is an approach that is not too 
> dissimilar to what we have done with MethodHandles - where many 
> seemingly different method handles are implemented under the hood by an 
> handful of shared lambda forms, which the JIT knows how to optimize well.
> 
> So yes, there's still an hop before getting into C++, but the hop is not 
> a jump into an opaque world, as it currently is for JNI; and that's 
> where Panama extension to the VM/runtime can and should provide extra 
> value.

That sounds great and all, but it has been almost 4 years now, and the 
only feedback I am getting is that it does not yet support function-like 
macros, inline functions, C++ templates, etc. Ok, then, when? Why is a 
"limited amount of wrappers" taking so long? It would be nice to have 
some sort of plan about where this is going! Maybe cooperating with the 
developers of Clang, get MSVC support in shape, and have Panama use 
that? Even Microsoft has their own fork these days:
     https://github.com/Microsoft/llvm
     https://github.com/Microsoft/clang
So they might be able to participate in this effort too! That would 
start to sound like a plan to me...

How do you see all this happening, if not with Clang?

Samuel