extern void validate_subarray (Lisp_Object, Lisp_Object, Lisp_Object,
ptrdiff_t, ptrdiff_t *, ptrdiff_t *);
extern Lisp_Object substring_both (Lisp_Object, ptrdiff_t, ptrdiff_t,
extern void validate_subarray (Lisp_Object, Lisp_Object, Lisp_Object,
ptrdiff_t, ptrdiff_t *, ptrdiff_t *);
extern Lisp_Object substring_both (Lisp_Object, ptrdiff_t, ptrdiff_t,