Re: [Chicken-users] FFI: wrapping method that returns object

[Felix Winkelmann]

Sergey Khorev wrote:
> Is there an easy way to teach Chicken to process the declarations below?
> Maybe some magic with ___declare(type,...)?
>
> #>!
> class T
> {
> public:
>     T() {}
>     int m(int i) { return i + 1 }
> };
>
> class A
> {
> public:
>     A() {}
>     T makeT()
>     {
>         T t;
>         return t;
>     }
> };
> <#
>
> Of course one can write wrapper like 
> T* makeT_() { return new T(makeT()); }
> But this is too boring, especially for dozens of such methods.

Sorry, no that is not possible. Chicken knows internally only
one type, the "C_word", a machine-sized typeless word (32 or
64 bit wide). Immediate values like fixnums and booleans are
marked words and everything else is a pointer. The makeT()
method above returns a non-pointer object, something we can
currently not handle.

One possible solution would be to create a piece of storage
and memcpy(..., ..., sizeof(T)) into it, passing this storage
around, but this may be a very dangerous thing to do, if T
does funky stuff, or prefers it's copy-constructor to be used.

Hm... I'll check this out. Perhaps we can kludge around this
problem somehow...


cheers,
felix