anchor.diff:    "Fires the callback attached to a notifier. Can be called from any thread."
     (let ((async-c (notifier-c notifier)))
       (uv:uv-async-send async-c)))
  +
  
positive.code: (defclass notifier ()
    ((c :accessor notifier-c :initarg :c :initform (cffi:null-pointer))
     (freed :accessor notifier-freed :reader notifier-freed-p :initform nil)
     (main-cb :accessor notifier-main-cb :initarg :main-cb :initform nil)
     (event-cb :accessor notifier-event-cb :initarg :event-cb :initform nil)
     (single-shot :accessor notifier-single-shot :reader notifier-single-shot-p
                  :initarg :single-shot :initform t))
    (:documentation "Wraps a threading-enabled notifier."))
  
negative.code: 
  (define-c-callback async-close-cb :void ((async-c :pointer))
    "Called when an async handle is closed."
    (free-pointer-data async-c :preserve-pointer t)
    (uv:free-handle async-c))
  
  (define-c-callback async-cb :void ((async-c :pointer))
    "Called when an async notifier is triggered."
    (let* ((notifier (deref-data-from-pointer async-c))
           (callbacks (get-callbacks async-c))
           (callback (getf callbacks :main-cb))
           (event-cb (getf callbacks :event-cb)))
      (catch-app-errors event-cb
        (unwind-protect
             (when callback (funcall callback))
  