A foreign pointer that may be a null pointer.
null-pointer-p returns true if ptr is a null
pointer and false otherwise.
CFFI> (null-pointer-p (null-pointer)) ⇒ T
(defun contains-str-p (big little) (not (null-pointer-p (foreign-funcall "strstr" :string big :string little :pointer)))) CFFI> (contains-str-p "Popcorns" "corn") ⇒ T CFFI> (contains-str-p "Popcorns" "salt") ⇒ NIL