* files.el (hack-local-variables-prop-line)

(hack-local-variables, dir-locals-read-from-file): Bind
read-circle to nil before reading.
* lread.c (Vread_circle): New variable.
(read1): Disable recursive read if Vread_circle is nil.

5 files changed, 32 insertions, 6 deletions

diff --git a/etc/NEWS b/etc/NEWS
index de3464ede22..a1246837c3e 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1931,6 +1931,10 @@ port support (see Emacs changes, above).
 ** Miscellaneous new variables
 
 +++
+*** `read-circle', if nil, disables the reading of recursive Lisp
+structures using the #N= and #N# syntax.
+
++++
 *** `this-command-keys-shift-translated' is non-nil if the key
 sequence invoking the current command was found by shift-translation.
 
diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 8d7881c1aa1..c93996b6ef0 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,9 @@
+2009-04-29  Ulrich Mueller  <ulm@gentoo.org>
+
+        * files.el (hack-local-variables-prop-line)
+        (hack-local-variables, dir-locals-read-from-file): Bind
+        read-circle to nil before reading.
+
 2009-04-28  Geert Kloosterman  <g.j.kloosterman@gmail.com>  (tiny change)
 
         * progmodes/which-func.el (which-function): Don't assume that
diff --git a/lisp/files.el b/lisp/files.el
index b14ccc2be5c..7b7c438df3c 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -2898,7 +2898,8 @@ and VAL is the specified value."
                (let ((key (intern (match-string 1)))
                      (val (save-restriction
                             (narrow-to-region (point) end)
-                            (read (current-buffer)))))
+                            (let ((read-circle nil))
+                              (read (current-buffer))))))
                  ;; It is traditional to ignore
                  ;; case when checking for `mode' in set-auto-mode,
                  ;; so we must do that here as well.
@@ -3044,12 +3045,14 @@ is specified, returning t if it is specified."
                   (if (eolp) (error "Missing colon in local variables entry"))
                   (skip-chars-backward " \t")
                   (let* ((str (buffer-substring beg (point)))
-                         (var (read str))
+                         (var (let ((read-circle nil))
+                                (read str)))
                          val)
                     ;; Read the variable value.
                     (skip-chars-forward "^:")
                     (forward-char 1)
-                    (setq val (read (current-buffer)))
+                    (let ((read-circle nil))
+                      (setq val (read (current-buffer))))
                     (if mode-only
                         (if (eq var 'mode)
                             (setq result t))
@@ -3348,7 +3351,8 @@ is found.  Returns the new class name."
     (insert-file-contents file)
     (let* ((dir-name (file-name-directory file))
            (class-name (intern dir-name))
-           (variables (read (current-buffer))))
+           (variables (let ((read-circle nil))
+                        (read (current-buffer)))))
       (dir-locals-set-class-variables class-name variables)
       (dir-locals-set-directory-class dir-name class-name
                                       (nth 5 (file-attributes file)))
diff --git a/src/ChangeLog b/src/ChangeLog
index d47f354ba6a..760795f1870 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2009-04-29  Ulrich Mueller  <ulm@gentoo.org>
+
+        * lread.c (Vread_circle): New variable.
+        (read1): Disable recursive read if Vread_circle is nil.
+
 2009-04-29  Kenichi Handa  <handa@m17n.org>
 
         * fontset.h (set_default_ascii_font): Delete extern.
diff --git a/src/lread.c b/src/lread.c
index 8a4b96874ce..cb3f5b04633 100644
--- a/src/lread.c
+++ b/src/lread.c
@@ -125,6 +125,9 @@ Lisp_Object Vload_file_name;
 /* Function to use for reading, in `load' and friends.  */
 Lisp_Object Vload_read_function;
 
+/* Non-nil means read recursive structures using #n= and #n# syntax.  */
+Lisp_Object Vread_circle;
+
 /* The association list of objects read with the #n=object form.
    Each member of the list has the form (n . object), and is used to
    look up the object for the corresponding #n# construct.
@@ -2558,7 +2561,7 @@ read1 (readcharfun, pch, first_in_list)
               c = READCHAR;
             }
           /* #n=object returns object, but associates it with n for #n#.  */
-          if (c == '=')
+          if (c == '=' && !NILP (Vread_circle))
             {
               /* Make a placeholder for #n# to use temporarily */
               Lisp_Object placeholder;
@@ -2580,7 +2583,7 @@ read1 (readcharfun, pch, first_in_list)
               return tem;
             }
           /* #n# returns a previously read object.  */
-          if (c == '#')
+          if (c == '#' && !NILP (Vread_circle))
             {
               tem = Fassq (make_number (n), read_objects);
               if (CONSP (tem))
@@ -4215,6 +4218,10 @@ read multiple times.  The list is in the same order as the symbols
 were read in. */);
   Vread_symbol_positions_list = Qnil;
 
+  DEFVAR_LISP ("read-circle", &Vread_circle,
+               doc: /* Non-nil means read recursive structures using #N= and #N# syntax.  */);
+  Vread_circle = Qt;
+
   DEFVAR_LISP ("load-path", &Vload_path,
                doc: /* *List of directories to search for files to load.
 Each element is a string (directory name) or nil (try default directory).