bug in save-some-buffers or diff.el?

[David Abrahams <dave@boost-consulting.com>]

Here's my backtrace:

Debugger entered--Lisp error: (wrong-type-argument stringp nil)
  expand-file-name(nil)
  find-file-noselect(nil)
  #[(file subexpr) "???Å ? )Ç\b??{!? ÉÊ\v!q×?	!? +B\fB?? [subexpr line save-match-data-internal file compilation-error-list beginning-of-line point-marker string-to-int match-data (...) find-file-noselect goto-line] 4](nil 2)
  diff-parse-differences(732 nil)
  compile-reinitialize-errors(nil 732)
  compilation-handle-exit(exit 1 "exited abnormally with code 1\n")
  compile-internal("diff -wu \"c:/src/emacs/README\" \"c:/DOCUME~1/dave/LOCALS~1/Temp/buffer-content-2644bjc\"" "No more differences" "Diff" diff-parse-differences nil nil nil nil nil nil t)
  diff("c:/src/emacs/README" "c:/DOCUME~1/dave/LOCALS~1/Temp/buffer-content-2644bjc" nil t)
  diff-buffer-with-file(#<buffer README>)
  funcall(diff-buffer-with-file #<buffer README>)
  (if (funcall (aref def 0) elt) (setq actions (1+ actions)) (setq next (\` ...)))
  (cond ((eq def ...) (setq next ...)) ((eq def ...) (funcall actor elt) (setq actions ...)) ((eq def ...)) ((eq def ...) (funcall actor elt) (setq actions ... next ...)) ((eq def ...) (setq quit-flag t) (setq next ...)) ((eq def ...) (if ... ...) (while ... ...)) ((eq def ...) (with-output-to-temp-buffer "*Help*" ... ...) (setq next ...)) ((vectorp def) (if ... ... ...)) ((and ... ...) (setq delayed-switch-frame char) (setq next ...)) (t (message "Type %s for help." ...) (beep) (sit-for 1) (setq next ...)))
  (cond ((stringp prompt) (setq quit-flag nil) (if use-menus ... ... ...) (cond ... ... ... ... ... ... ... ... ... ...)) (prompt (funcall actor elt) (setq actions ...)))
  (while (funcall next) (setq prompt (funcall prompter elt)) (cond (... ... ... ...) (prompt ... ...)))
  (progn (if (stringp prompter) (setq prompter ...)) (while (funcall next) (setq prompt ...) (cond ... ...)))
  (unwind-protect (progn (if ... ...) (while ... ... ...)) (if delayed-switch-frame (setq unread-command-events ...)))
  (let* ((actions 0) user-keys mouse-event map prompt char elt tail def use-menus delayed-switch-frame (next ...)) (if (and ... use-dialog-box) (let ... ...) (setq user-keys ... map ...)) (unwind-protect (progn ... ...) (if delayed-switch-frame ...)) (let (...) (message "")) actions)
  map-y-or-n-p(#[(buffer) "Å!?


Here's how I get there:

1. Run emacs with -q

1.5 `M-x set-variable RET debug-on-error RET t'

2. open emacs' README file

3. Go to the beginning of line 48

4. Type `X'

5. Type `C-x s'

6. Type `d'

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com