anchor.diff:      (alloc-pair-plus-one 1 2 3)
     ((1 . 2) . 3))
   
  -#+#:unimplemented
   (defcfun "pair_sum" :int
  -  (p (:struct pair)))
  -
  -#+#:unimplemented
  -(defcfun "make_pair" (:struct pair)
  +  (p (:struct struct-pair)))
  +
  +(defcfun "make_pair" (:struct struct-pair)
     (a :int)
     (b :int))
   
  -#|| ; TODO: load cffi-libffi for these tests to work.
   (deftest struct-values.fn.1
  -    (with-foreign-object (p '(:struct pair))
  -      (with-foreign-slots ((a b) p (:struct pair))
  -        (setf a -1 b 2)
  -        (pair-sum p)))
  +    (pair-sum '(-1 . 2))
     1)
   
   (deftest struct-values.fn.2
  -    (pair-sum '(3 . 5))
  -  8)
  -
  -(deftest struct-values.fn.3
  -    (with-foreign-object (p '(:struct pair))
  -      (make-pair 7 11 :result-pointer p)
  -      (with-foreign-slots ((a b) p (:struct pair))
  -        (cons a b)))
  -  (7 . 11))
  -
  -(deftest struct-values.fn.4
       (make-pair 13 17)
     (13 . 17))
  -||#
   
   (defcstruct single-byte-struct
     (a :uint8))
  
positive.code:   (1 . 2)
    (3 . 4))
  
  (defcstruct (struct-pair-default-translate :class pair-default)
    (a :int)
    (b :int))
  
  
negative.code:   1
    2)
  
  (defcstruct (struct-pair+double)
    (pr (:struct struct-pair-default-translate))
    (dbl :double))
  
  