anchor.diff:    fd)
   
   (defun %with-fd-scope (fn &optional bindings)
  +  "The function that implements `with-fd-scope'."
     (let* ((*fd-bindings* (or bindings *fd-bindings* (fset:empty-map)))
            (*autorelease-fd-scope* (make-extensible-vector :element-type 'integer)))
       ;; Retain the new bindings
  
positive.code:     (posix-write fd (make-array 1 :initial-element byte :element-type '(unsigned-byte 8)))))
  
  (defmacro with-fd-streams (() &body body)
    `(let ((*standard-input* (make-instance 'fd-character-input-stream :fd 0 :symbolic t))
           (*standard-output* (make-instance 'fd-character-output-stream :fd 1 :symbolic t))
           (*error-output* (make-instance 'fd-character-output-stream :fd 2 :symbolic t)))
       ,@body))
  
  (defun make-binary-fd-stream (fd direction symbolic)
    (macrolet
        ((make (type)
           `(make-instance ',type :symbolic symbolic :fd fd)))
  
negative.code:       (debug-log status "SIMPLIFIED ~A" fd-bindings)
        fd-bindings)))
  
  (defun simplify-fd-bindings ()
    "Produce a version of the current fd bindings which is safe to
  naively apply via dup2 in a child process."
    (%simplify-fd-bindings *fd-bindings* (lambda (fd) (fd-autorelease (dup-retained fd)))))
  
  (defclass fd-stream (fundamental-stream)
    ((fd
      :initarg :fd
      :type (or integer null)
      :initform (required)
      :documentation
      "The file descriptor this stream interacts with.")
     (symbolic
      :initarg :symbolic
      :initform nil
      :documentation
      "Non-nil if this stream should evaluate the given fd in the
  context of the current fd bindings.
  
  If this slot is non-nil, then a call to `bind-fd' could change which
  file descriptor is actually being interacted with.  If this slot is
  nil, then the stream will disregard the fd bindings and just interact
  with the given fd."))
    (:documentation
     "A stream which interacts with a file descriptor."))
  
  (defgeneric fd-stream-fd (stream)
    (:documentation
     "Return the actual file descriptor that the stream is currently
  with."))
  (defmethod fd-stream-fd ((stream fd-stream))
    (with-slots (symbolic fd) stream
      (if symbolic
  