compilation-process-setup-function doc bug?

[Paul Michael Reilly]

I believe the documentation string for the variable
compilation-process-setup-function is wrong or less than clear.
It says:

  *Function to call to customize the compilation process.
  This function is called immediately before the compilation process is
  started.  It can be used to set any variables or functions that are
  used while processing the output of the compilation process.  The
  function is called with variables `compilation-buffer' and
  `compilation-window' bound to the compilation buffer and window,
  respectively.

What does this mean actually?  In my blissful ignorance I thought
it meant I should create a function like so:

(defun test (compilation-buffer compilation-window)
  ...)

and do

(setq compilation-process-setup-function 'test)

but when I do M-x compile, Emacs is not happy with the arguments.
It is actually called with no arguments.  So next I'm thinking maybe 
this is what the documentation means:

(defun test ()
  (message "The args are %s %s" compilation-buffer compilation-window)
  ...)

but Emacs complains that the variables are void, which seems reasonable. 
 My take is that the last sentence in the doc string should be 
expunged.  Am I correct?

-pmr