Re: ffi & double[]

[Bruno H. <br...@cl...>]

Sam wrote:
> does CLISP FFI support double arrays?
> 
> --------- sum.c -------------------
> double sum (int len, double *vec) {
>   int i;
>   double s=0;
>   for (i=0; i<len; i++) s+= vec[i];
>   return s;
> }
> --------- sum.c -------------------
> gcc -shared -o libsum.so sum.c
> 
> (def-call-out sum (:name "sum") (:library "libsum.so") (:language :stdc)
>   (:return-type double-float)
>   (:arguments (n int) (v (c-array-max double-float 10))))
> 
> (sum 0 #()) ==> 0d0
> (sum 3 #(1d0 2d0 3d0)) ==> segfault (at NULL)

This is normal. Your declaration (def-call-out sum ...)
corresponds to

    double sum (int len, double v[10]);

which means that 10 doubles are passed on the stack. Whereas sum.c defines
a function that expects on the stack a _pointer_ to 10 doubles. So the CPU
is now interpreting the first half of a 'double' value as a pointer, and
it must crash.

Bruno