From cb46d8443010d208077152c70a8d11ea8f10ba9e Mon Sep 17 00:00:00 2001
From: mig <mig>
Date: Wed, 13 Apr 2011 13:09:19 +0000
Subject: fix for [Bug 2662380], crash caused by appending to a variable with a
 write trace that unsets it

---
 ChangeLog        | 5 +++++
 generic/tclVar.c | 3 ++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/ChangeLog b/ChangeLog
index 1ee1018..2ff7fc6 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2011-04-13  Miguel Sofer  <msofer@users.sf.net>
+
+	* generic/tclVar.c: fix for [Bug 2662380], crash caused by
+	appending to a variable with a write trace that unsets it.
+
 2011-04-04  Don Porter  <dgp@users.sourceforge.net>
 
 	* README:	Updated README files, repairing broken URLs and
diff --git a/generic/tclVar.c b/generic/tclVar.c
index 3312191..a434bae 100644
--- a/generic/tclVar.c
+++ b/generic/tclVar.c
@@ -2699,7 +2699,8 @@ Tcl_AppendObjCmd(dummy, interp, objc, objv)
 
 	    varValuePtr = TclPtrSetVar(interp, varPtr, arrayPtr, part1, NULL, 
 	            objv[i], (TCL_APPEND_VALUE | TCL_LEAVE_ERR_MSG));
-	    if (varValuePtr == NULL) {
+	    if ((varValuePtr == NULL) ||
+		    (varValuePtr == ((Interp *) interp)->emptyObjPtr)) {
 		return TCL_ERROR;
 	    }
 	}
-- 
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