[Haskell-cafe] Re: Could FFI support pass-by-value of structs?

[Henning Thielemann]

Maurí­cio schrieb:
>>> It's not usual, but it is allowed to have values of
>>> structs passed between functions directly instead of
>>> using pointers: (...)
> 
>>> Would it be possible to allow that in Haskell FFI (...)
> 
>> There are a couple problems with this. First, the storage layout for a
>> given C struct may be radically different depending on the back end,
> 
> When you say struct layout, do you mean the offset of diferent
> fields? I don't think this would be a problem, as your sugestion
> of hsc2hs is one of many solutions to that. I'm not sugesting
> that peek and poke methods of Storage instances should be created
> automatically, I understand this would not worth the effort.
> 
> However, isn't just knowing the size and alignment enough to
> write a generic struct handler that, by using the appropriate
> calling convention, is going to work with any struct? If not,
> I agree with you it's really not worth it (as we can use pointers
> as Felipe sugested.

I tried that in
  http://hackage.haskell.org/package/storable-record/