anchor.diff:    (:report (lambda (c s) (format s "Can't enter FD ~A into retain/release management again" (fd-already-managed-fd c)))))
   
   (defun %manage-new-fd (fd)
  +  "Enter the given fd into the retain/release table."
     (when (gethash fd %fd-retain-count-table%)
       (error 'fd-already-managed :fd fd))
     (setf (gethash fd %fd-retain-count-table%) 1)
  
positive.code:   (declare (ignore r))
    (logior sb-posix:o-rdwr sb-posix:o-creat))
  
  (defgeneric fd-from-description (description))
  (defmethod fd-from-description ((fd integer))
    fd)
  (defmethod fd-from-description ((io-file io-file))
  
negative.code:              (,write-end (fd-autorelease ,raw-write-end)))
           ,@body))))
  
  (defgeneric open-args-for-redirect (redirect)
    (:documentation
     "Returns the flags that should be passed to the posix open function
  for the given redirect."))
  (defmethod open-args-for-redirect ((r less))
    (declare (ignore r))
    (logior sb-posix:o-rdonly))
  