--- a/UndefObj.st	Fri Jun 25 18:01:47 1999 +0200
+++ b/UndefObj.st	Sat Jun 26 15:50:58 1999 +0200
@@ -126,6 +126,16 @@
     ^ true
 
     "Created: 3.6.1997 / 12:01:39 / cg"
+!
+
+isBuiltInClass
+    "return true, if this class is known by the run-time-system,
+     i.e. you cannot add/remove instance variables without recompiling
+     the VM.
+     Here, true is returned for myself, false for subclasses."
+
+    ^ self == UndefinedObject
+
 ! !
 
 !UndefinedObject methodsFor:'converting'!
@@ -517,6 +527,6 @@
 !UndefinedObject class methodsFor:'documentation'!
 
 version
-    ^ '$Header: /cvs/stx/stx/libbasic/Attic/UndefObj.st,v 1.38 1999-03-19 07:27:31 stefan Exp $'
+    ^ '$Header: /cvs/stx/stx/libbasic/Attic/UndefObj.st,v 1.39 1999-06-26 13:50:58 cg Exp $'
 ! !
 UndefinedObject initialize!

--- a/UndefinedObject.st	Fri Jun 25 18:01:47 1999 +0200
+++ b/UndefinedObject.st	Sat Jun 26 15:50:58 1999 +0200
@@ -126,6 +126,16 @@
     ^ true
 
     "Created: 3.6.1997 / 12:01:39 / cg"
+!
+
+isBuiltInClass
+    "return true, if this class is known by the run-time-system,
+     i.e. you cannot add/remove instance variables without recompiling
+     the VM.
+     Here, true is returned for myself, false for subclasses."
+
+    ^ self == UndefinedObject
+
 ! !
 
 !UndefinedObject methodsFor:'converting'!
@@ -517,6 +527,6 @@
 !UndefinedObject class methodsFor:'documentation'!
 
 version
-    ^ '$Header: /cvs/stx/stx/libbasic/UndefinedObject.st,v 1.38 1999-03-19 07:27:31 stefan Exp $'
+    ^ '$Header: /cvs/stx/stx/libbasic/UndefinedObject.st,v 1.39 1999-06-26 13:50:58 cg Exp $'
 ! !
 UndefinedObject initialize!