From 98c6b22c1002fae94f8abf7422758530a9a6fdeb Mon Sep 17 00:00:00 2001
From: dgp <dgp@users.sourceforge.net>
Date: Wed, 8 Nov 2017 02:21:49 +0000
Subject: TclOO object allocation: Set classPtr to NULL if it wasn't otherwise
 set.

---
 generic/tclOO.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/generic/tclOO.c b/generic/tclOO.c
index ec666ee..f236ac9 100644
--- a/generic/tclOO.c
+++ b/generic/tclOO.c
@@ -537,7 +537,8 @@ KillFoundation(
  * AllocObject --
  *
  *	Allocate an object of basic type. Does not splice the object into its
- *	class's instance list.
+ *	class's instance list.  The caller must set the classPtr on the object,
+ *	either to a class or to NULL.
  *
  * ----------------------------------------------------------------------
  */
@@ -1672,6 +1673,8 @@ Tcl_NewObjectInstance(
 	AllocClass(interp, oPtr);
 	oPtr->selfCls = classPtr;
 	TclOOAddToSubclasses(oPtr->classPtr, fPtr->objectCls);
+    } else {
+	oPtr->classPtr = NULL;
     }
 
     /*
-- 
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