Fix and doc-fix for `buffer-local-variables'.

* src/buffer.c (Fbuffer_local_variables)
(buffer_lisp_local_variables): Handle unbound vars correctly;
don't let Qunbound leak into Lisp.

* doc/lispref/variables.texi (Creating Buffer-Local): Minor clarification
to buffer-local-variables doc.

Fixes: debbugs:10715

2 files changed, 16 insertions, 4 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 5e4d995d857..71af862cdac 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,9 @@
+2012-02-07  Chong Yidong  <cyd@gnu.org>
+
+	* buffer.c (Fbuffer_local_variables)
+	(buffer_lisp_local_variables): Handle unbound vars correctly;
+	don't let Qunbound leak into Lisp.
+
 2012-02-07  Glenn Morris  <rgm@gnu.org>
 
 	* image.c (Fimagemagick_types): Doc fix.
diff --git a/src/buffer.c b/src/buffer.c
index 01418956c8d..a6f61a1936a 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -1022,7 +1022,10 @@ buffer_lisp_local_variables (struct buffer *buf)
       if (buf != current_buffer)
 	val = XCDR (elt);
 
-      result = Fcons (Fcons (XCAR (elt), val), result);
+      result = Fcons (EQ (val, Qunbound)
+		      ? XCAR (elt)
+		      : Fcons (XCAR (elt), val),
+		      result);
     }
 
   return result;
@@ -1064,9 +1067,12 @@ No argument or nil as argument means use current buffer as BUFFER.  */)
 	idx = PER_BUFFER_IDX (offset);
 	if ((idx == -1 || PER_BUFFER_VALUE_P (buf, idx))
 	    && SYMBOLP (PER_BUFFER_SYMBOL (offset)))
-	  result = Fcons (Fcons (PER_BUFFER_SYMBOL (offset),
-				 PER_BUFFER_VALUE (buf, offset)),
-			  result);
+	  {
+	    Lisp_Object sym = PER_BUFFER_SYMBOL (offset);
+	    Lisp_Object val = PER_BUFFER_VALUE (buf, offset);
+	    result = Fcons (EQ (val, Qunbound) ? sym : Fcons (sym, val),
+			    result);
+	  }
       }
   }