0.8.7.47:

(def-format-interpreter #\W (colonp atsignp params)

  (interpret-bind-defaults () params

    (let ((*print-pretty* (or colonp *print-pretty*))

	  (*print-level* (and atsignp *print-level*))

	  (*print-length* (and atsignp *print-length*)))

	  (*print-level* (unless atsignp *print-level*))

	  (*print-length* (unless atsignp *print-length*)))

      (output-object (next-arg) stream))))

;;;; format interpreters and support functions for integer output

;;; violations through stack corruption.

(print 0.0001)

;;; In sbcl-0.8.7, the ~W format directive interpreter implemented the

;;; sense of the colon and at-sign modifiers exactly backwards.

;;;

;;; (Yes, the test for this *is* substantially hairier than the fix;

;;; wanna make something of it?)

(cl:in-package :cl-user)

(defstruct wexerciser-0-8-7)

(defun wexercise-0-8-7-interpreted (wformat)

  (format t wformat (make-wexerciser-0-8-7)))

(defmacro define-compiled-wexercise-0-8-7 (wexercise wformat)

  `(defun ,wexercise ()

    (declare (optimize (speed 3) (space 1)))

    (format t ,wformat (make-wexerciser-0-8-7))

    (values)))

(define-compiled-wexercise-0-8-7 wexercise-0-8-7-compiled-without-atsign "~W")

(define-compiled-wexercise-0-8-7 wexercise-0-8-7-compiled-with-atsign "~@W")

(defmethod print-object :before ((wexerciser-0-8-7 wexerciser-0-8-7) stream)

  (unless (and *print-level* *print-length*)

    (error "gotcha coming")))

(let ((*print-level* 11)

      (*print-length* 12))

  (wexercise-0-8-7-interpreted "~W")

  (wexercise-0-8-7-compiled-without-atsign))

(remove-method #'print-object

	       (find-method #'print-object

			    '(:before)

			    (mapcar #'find-class '(wexerciser-0-8-7 t))))

(defmethod print-object :before ((wexerciser-0-8-7 wexerciser-0-8-7) stream)

  (when (or *print-level* *print-length*)

    (error "gotcha going")))

(let ((*print-level* 11)

      (*print-length* 12))

  (wexercise-0-8-7-interpreted "~@W")

  (wexercise-0-8-7-compiled-with-atsign))

;;; success

(quit :unix-status 104)

;;; checkins which aren't released. (And occasionally for internal

;;; versions, especially for internal versions off the main CVS

;;; branch, it gets hairier, e.g. "0.pre7.14.flaky4.13".)

"0.8.7.46"

"0.8.7.47"