From 0d3e2f0116da21f2c52ef225148e17555d4be6ff Mon Sep 17 00:00:00 2001
From: hobbs <hobbs>
Date: Mon, 10 Sep 2007 23:05:45 +0000
Subject: 	* generic/tclLink.c (Tcl_UpdateLinkedVar): guard against var
 being 	unlinked. [Bug 1740631] (maros)

---
 ChangeLog         |  5 +++++
 generic/tclLink.c | 11 +++++++++--
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 48fc551..5276c37 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2007-09-10  Jeff Hobbs  <jeffh@ActiveState.com>
+
+	* generic/tclLink.c (Tcl_UpdateLinkedVar): guard against var being
+	unlinked. [Bug 1740631] (maros)
+
 2007-09-10  Miguel Sofer  <msofer@users.sf.net>
 
 	* generic/tclCompile.c: fix tclInstructionTable entry for
diff --git a/generic/tclLink.c b/generic/tclLink.c
index 0f33c03..59eb70f 100644
--- a/generic/tclLink.c
+++ b/generic/tclLink.c
@@ -12,7 +12,7 @@
  * See the file "license.terms" for information on usage and redistribution of
  * this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tclLink.c,v 1.22 2007/05/07 19:45:33 dgp Exp $
+ * RCS: @(#) $Id: tclLink.c,v 1.23 2007/09/10 23:05:46 hobbs Exp $
  */
 
 #include "tclInt.h"
@@ -215,7 +215,14 @@ Tcl_UpdateLinkedVar(
     linkPtr->flags |= LINK_BEING_UPDATED;
     Tcl_ObjSetVar2(interp, linkPtr->varName, NULL, ObjValue(linkPtr),
 	    TCL_GLOBAL_ONLY);
-    linkPtr->flags = (linkPtr->flags & ~LINK_BEING_UPDATED) | savedFlag;
+    /*
+     * Callback may have unlinked the variable. [Bug 1740631]
+     */
+    linkPtr = (Link *) Tcl_VarTraceInfo(interp, varName, TCL_GLOBAL_ONLY,
+	    LinkTraceProc, (ClientData) NULL);
+    if (linkPtr != NULL) {
+	linkPtr->flags = (linkPtr->flags & ~LINK_BEING_UPDATED) | savedFlag;
+    }
 }
 
 /*
-- 
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