Re: [Chicken-users] FFI: Safe referencing and allocation of Scheme objects from C

[felix]

On Mon, 10 Nov 2003 15:04:19 +0000, Category 5 <address@hidden> 
wrote:

> The calling function expects it to take an (unsigned char *), so
> changing the declaration causes warnings.  However, I went ahead and
> tried changing it to:
>
> (define-external (scheme_callback_func (scheme-object x))
> void
> (let ((p x))
> (assert (procedure? p))
> (p ...)))

That's better.

> I also played around with the C_alloc_in_heap case a little more.  The
> call to that function itself succeeds and returns a pointer that looks
> good; the fireworks start when the callback function is called.  The
> process immediately begins spinning, using 100% CPU.  I can get a print
> from the callback function to come through, but as soon as it tries to
> call the procedure passed in as x above, it goes into never-never land;
> not even a print at the beginning of the-procedure-x-points-to comes
> through.
>
> Very odd, especially since just replacing C_alloc_in_heap with malloc
> makes everything run happily.

The only thing that comes to mind is that either the heap-allocated object
does not get passed properly, or that C_alloc_in_heap is simply buggy.
I'll investigate this...


cheers,
felix