(import foreign)

(foreign-declare #<<EOF

typedef struct {
    double u;
    double v;
    double w;
    double x;
    double y;
    void* hah;
    double z;
} c_struct_t;


void fill_struct (c_struct_t* s, double val){
  s->z = val;
}

EOF
)

(define-foreign-variable sizeof-c-struct size_t "sizeof(c_struct_t)")
(define-record c-struct-type buffer)
(let ((maker make-c-struct-type))
  (set! make-c-struct-type
    (lambda () (maker (make-blob sizeof-c-struct)))))

(define-foreign-type c-struct-t scheme-pointer)

(define fill-struct (foreign-lambda void "fill_struct" c-struct-t double))
(define c-struct-t-z (foreign-lambda* double ((c-struct-t t)) "C_return(((c_struct_t*)t)->z);"))

(print "sizeof c struct: " sizeof-c-struct)

(let loop ((i 0.23))
  (let ((s (c-struct-type-buffer (make-c-struct-type)))) ;; <-- Buffer accessor used here
    (fill-struct s i)
    (print i " == " (c-struct-t-z s)))
  (loop (add1 i)))