anchor.diff:                 :documentation "Keyword identifier, or NIL.")
      (message :initarg :message :reader message-of
               :documentation "Error description."))
  -  (:default-initargs :code nil :identifier :unknown))
  +  (:default-initargs :code nil :identifier :unknown :message nil))
   
   (define-condition system-error (error condition-info-mixin)
     ()
  
positive.code:   ((event-type :initarg :event-type :reader event-type-of)
     (os-handle :initarg :os-handle :reader os-handle-of))
    (:report (lambda (c s)
               (format s "Poll error(event ~S, handle ~A): ~A"
                       (event-type-of c) (os-handle-of c) (message-of c))))
    (:documentation
     "Signaled when an error occurs while polling for I/O readiness
  of a file descriptor."))
  
negative.code:   ((event-type :initarg :event-type :reader event-type-of)
     (os-handle :initarg :os-handle :reader os-handle-of))
    (:report (lambda (c s)
               (format s "Poll timeout(event ~S, handle ~A)"
                       (event-type-of c) (os-handle-of c))
               (when (message-of c)
                 (format s ": ~A" (message-of c)))))
    (:documentation
     "Signaled when a timeout occurs while polling for I/O readiness
  of a file descriptor."))
  