downcalls, fixed-sized ABI types

[Maurizio Cimadamore]

There needs to be a discussion on what kind of layout constants should 
be provided.

In the old repo we had a combination which, I think, worked well - there 
were _both_ ABI-specific constants (say - if you wanted to specifically 
target a platform, these are good targets for jextract). But there were 
also platform-agnostic constants like C_INT, which were dynamically 
bound to the right ABI-dependent constant. I think having these would be 
helpful, plus the addition of some more, like SIZE_T etc.

So, yes, work in progress.

Maurizio

On 20/01/2020 04:01, Michael Zucchi wrote:
>
> Hi guys,
>
> I suspect this is still somewhat 'work in progress', but when creating 
> downcall method handles you need to use the annotated ValueLayouts in 
> the FunctionDescriptor but these only contain the arbitrary 'c' sizes 
> from the standard platform compiler.
>
> But this misses some important types like size_t, intptr_t, or the 
> stdint types.  So to map to those you need to know both the size the 
> type and the size of the integral types you're mapping to, and not 
> just it's symbolic base name.  It would be convenient if the sized 
> types worked or were available since that is the most fundamental 
> information you get from the c compiler.
>
> If you know all this information already, the ABI stuff just seems 
> redundant.  And the way the abi definitions are accessed also seems 
> counter to creating dynamic cross-platform code, at least without a 
> bunch of extra scaffolding.
>
> Thanks,
>  Michael
>