- (declare (simple-string pathname))
- (let ((len (length pathname))
- (pending pathname))
- (declare (fixnum len) (simple-string pending))
- (if (zerop len)
- pathname
- (let ((result (make-string 1024 :initial-element (code-char 0)))
- (fill-ptr 0)
- (name-start 0))
- (loop
- (let* ((name-end (or (position #\/ pending :start name-start) len))
- (new-fill-ptr (+ fill-ptr (- name-end name-start))))
- (replace result pending
- :start1 fill-ptr
- :end1 new-fill-ptr
- :start2 name-start
- :end2 name-end)
- (let ((kind (unix-file-kind (if (zerop name-end) "/" result) t)))
- (unless kind (return nil))
- (cond ((eq kind :link)
- (multiple-value-bind (link err) (unix-readlink result)
- (unless link
- (error 'simple-file-error
- :pathname pathname
- :format-control
- "~@<error reading link ~S: ~2I~_~A~:>"
- :format-arguments (list (subseq
- result 0 fill-ptr)
- (strerror err))))
- (cond ((or (zerop (length link))
- (char/= (schar link 0) #\/))
- ;; It's a relative link.
- (fill result (code-char 0)
- :start fill-ptr
- :end new-fill-ptr))
- ((string= result "/../" :end1 4)
- ;; It's across the super-root.
- (let ((slash (or (position #\/ result :start 4)
- 0)))
- (fill result (code-char 0)
- :start slash
- :end new-fill-ptr)
- (setf fill-ptr slash)))
- (t
- ;; It's absolute.
- (and (> (length link) 0)
- (char= (schar link 0) #\/))
- (fill result (code-char 0) :end new-fill-ptr)
- (setf fill-ptr 0)))
- (setf pending
- (if (= name-end len)
- link
- (concatenate 'simple-string
- link
- (subseq pending name-end))))
- (setf len (length pending))
- (setf name-start 0)))
- ((= name-end len)
- (return (subseq result 0 new-fill-ptr)))
- ((eq kind :directory)
- (setf (schar result new-fill-ptr) #\/)
- (setf fill-ptr (1+ new-fill-ptr))
- (setf name-start (1+ name-end)))
- (t
- (return nil))))))))))
+ (declare (type simple-string pathname))
+ (aver (not (relative-unix-pathname? pathname)))
+ (/noshow "entering UNIX-RESOLVE-LINKS")
+ (loop with previous-pathnames = nil do
+ (/noshow pathname previous-pathnames)
+ (let ((link (unix-readlink pathname)))
+ (/noshow link)
+ ;; Unlike the old CMU CL code, we handle a broken symlink by
+ ;; returning the link itself. That way, CL:TRUENAME on a
+ ;; broken link returns the link itself, so that CL:DIRECTORY
+ ;; can return broken links, so that even without
+ ;; Unix-specific extensions to do interesting things with
+ ;; them, at least Lisp programs can see them and, if
+ ;; necessary, delete them. (This is handy e.g. when your
+ ;; managed-by-Lisp directories are visited by Emacs, which
+ ;; creates broken links as notes to itself.)
+ (if (null link)
+ (return pathname)
+ (let ((new-pathname
+ (unix-simplify-pathname
+ (if (relative-unix-pathname? link)
+ (let* ((dir-len (1+ (position #\/
+ pathname
+ :from-end t)))
+ (dir (subseq pathname 0 dir-len)))
+ (/noshow dir)
+ (concatenate 'string dir link))
+ link))))
+ (if (unix-file-kind new-pathname)
+ (setf pathname new-pathname)
+ (return pathname)))))
+ ;; To generalize the principle that even if portable Lisp code
+ ;; can't do anything interesting with a broken symlink, at
+ ;; least it should be able to see and delete it, when we
+ ;; detect a cyclic link, we return the link itself. (So even
+ ;; though portable Lisp code can't do anything interesting
+ ;; with a cyclic link, at least it can see it and delete it.)
+ (if (member pathname previous-pathnames :test #'string=)
+ (return pathname)
+ (push pathname previous-pathnames))))