Index: generic/nsf.c
===================================================================
diff -u -r0d57967b71cec0802c109bdef6aef37d85a817a2 -re89a635d134e85db66c3e7059ec81817b6b36ea5
--- generic/nsf.c	(.../nsf.c)	(revision 0d57967b71cec0802c109bdef6aef37d85a817a2)
+++ generic/nsf.c	(.../nsf.c)	(revision e89a635d134e85db66c3e7059ec81817b6b36ea5)
@@ -2959,7 +2959,11 @@
    * perform the merge operation. For n elements in superClasses, the merge
    * operation is performed n-1 times.
    */
-  for (sl = superClasses->nextPtr; sl != NULL; sl = sl->nextPtr) {
+
+  sl = superClasses->nextPtr;
+  assert(superClasses->nextPtr != NULL);
+
+  do {
     NsfClasses *mergeList = sl->cl->order, *baseListCurrent;
 
 #if defined(NSF_LINEARIZER_TRACE)
@@ -3078,7 +3082,11 @@
       pl = NULL;
       plNext = NsfClassListAdd(&pl, class, NULL);
     }
-  }
+    /*
+     * Get next element from the list.
+     */
+    sl = sl->nextPtr;
+  } while (sl != NULL);
 
   for (sl = deletionList; sl != NULL; sl = sl->nextPtr) {
     /* fprintf(stderr, "delete from deletion list %p client data %p\n", sl, sl->clientData); */
@@ -6507,7 +6515,7 @@
            entryPtr != NULL;
            entryPtr = Tcl_NextHashEntry(&search)) {
         Tcl_Obj *nameObj;
-        Var *varPtr;
+        Var     *varPtr;
 
         GetVarAndNameFromHash(entryPtr, &varPtr, &nameObj);
         if ((varPtr->flags & VAR_TRACED_UNSET) != 0u /* TclIsVarTraced(varPtr) */) {
@@ -29731,17 +29739,16 @@
 */
 static int
 NsfNSCopyVarsCmd(Tcl_Interp *interp, Tcl_Obj *fromNsObj, Tcl_Obj *toNsObj) {
-  Tcl_Namespace *fromNsPtr = NULL, *toNsPtr;
-  Var *varPtr = NULL;
-  Tcl_HashSearch hSrch;
+  Tcl_Namespace       *fromNsPtr = NULL, *toNsPtr;
+  Var                 *varPtr = NULL;
+  Tcl_HashSearch       hSrch;
   const Tcl_HashEntry *hPtr;
-  TclVarHashTable *varTablePtr;
-  NsfObject *object, *destObject;
-  const char *destFullName;
-  Tcl_Obj *destFullNameObj;
-  Tcl_CallFrame frame, *framePtr = &frame;
-  Tcl_Obj *varNameObj = NULL;
-  int      result;
+  TclVarHashTable     *varTablePtr;
+  NsfObject           *destObject;
+  const char          *destFullName;
+  Tcl_Obj             *destFullNameObj;
+  Tcl_CallFrame        frame, *framePtr = &frame;
+  int                  result;
 
   nonnull_assert(interp != NULL);
   nonnull_assert(fromNsObj != NULL);
@@ -29755,14 +29762,13 @@
                            ObjStr(toNsObj));
     }
 
-    object = GetObjectFromString(interp, ObjStr(fromNsObj));
     destFullName = toNsPtr->fullName;
     destFullNameObj = Tcl_NewStringObj(destFullName, -1);
     INCR_REF_COUNT(destFullNameObj);
     varTablePtr = Tcl_Namespace_varTablePtr(fromNsPtr);
     Tcl_PushCallFrame(interp, (Tcl_CallFrame *)framePtr, toNsPtr, 0);
   } else {
-    NsfObject *newObject;
+    NsfObject *newObject, *object;
 
     if (GetObjectFromObj(interp, fromNsObj, &object) != TCL_OK) {
       return NsfPrintError(interp, "CopyVars: Origin object/namespace %s does not exist",
@@ -29786,7 +29792,7 @@
    */
   hPtr = (varTablePtr != NULL) ? Tcl_FirstHashEntry(TclVarHashTablePtr(varTablePtr), &hSrch) : NULL;
   while (hPtr != NULL) {
-    Tcl_Obj *resultObj;
+    Tcl_Obj *varNameObj, *resultObj;
 
     GetVarAndNameFromHash(hPtr, &varPtr, &varNameObj);
     INCR_REF_COUNT(varNameObj);
@@ -29795,11 +29801,11 @@
       if (TclIsVarScalar(varPtr)) {
         /*
          * Copy scalar variables from the namespace, which might be
-         * either object or namespace variables.
+         * either instance or namespace variables.
          */
 
         if (destObject != NULL) {
-          /* fprintf(stderr, "copy in obj %s var %s val '%s'\n", ObjectName(object), ObjStr(varNameObj),
+          /* fprintf(stderr, "copy in obj %s var %s val '%s'\n", ObjectName(destObject), ObjStr(varNameObj),
              ObjStr(TclVarValue(Tcl_Obj, varPtr, objPtr)));*/
 
           resultObj = Nsf_ObjSetVar2((Nsf_Object *)destObject, interp, varNameObj, NULL,
@@ -29829,7 +29835,7 @@
             INCR_REF_COUNT(eltNameObj);
 
             if (TclIsVarScalar(eltVar)) {
-              if (object != NULL) {
+              if (destObject != NULL) {
                 resultObj = Nsf_ObjSetVar2((Nsf_Object *)destObject, interp, varNameObj, eltNameObj,
                                            TclVarValue(Tcl_Obj, eltVar, objPtr), TCL_LEAVE_ERR_MSG);
               } else {
@@ -34608,6 +34614,7 @@
          entryPtr = Tcl_NextHashEntry(&search)) {
       Tcl_Obj *nameObj;
       Var *varPtr;
+
       GetVarAndNameFromHash(entryPtr, &varPtr, &nameObj);
       if (!TclIsVarUndefined(varPtr) || TclIsVarNamespaceVar(varPtr)) {
         /* fprintf(stderr, "unsetting var %s\n", ObjStr(nameObj));*/
Index: generic/nsfStack.c
===================================================================
diff -u -r7aad1f9b1cd757ef50182bdef2bbbf401a866862 -re89a635d134e85db66c3e7059ec81817b6b36ea5
--- generic/nsfStack.c	(.../nsfStack.c)	(revision 7aad1f9b1cd757ef50182bdef2bbbf401a866862)
+++ generic/nsfStack.c	(.../nsfStack.c)	(revision e89a635d134e85db66c3e7059ec81817b6b36ea5)
@@ -638,53 +638,59 @@
                                Tcl_CallFrame **callingProcFramePtrPtr,
                                Tcl_CallFrame **callingFramePtrPtr) {
   register Tcl_CallFrame *varFramePtr;
-  int                     lvl;
 
   nonnull_assert(interp != NULL);
 
   varFramePtr = (Tcl_CallFrame *)Tcl_Interp_varFramePtr(interp);
-  lvl = Tcl_CallFrame_level(varFramePtr);
+  if (likely(varFramePtr != NULL)) {
+    int lvl = Tcl_CallFrame_level(varFramePtr);
 
-  for (; likely(varFramePtr != NULL); varFramePtr = Tcl_CallFrame_callerVarPtr(varFramePtr)) {
-    register unsigned int flags = (unsigned int)Tcl_CallFrame_isProcCallFrame(varFramePtr);
+    do {
+      register unsigned int flags = (unsigned int)Tcl_CallFrame_isProcCallFrame(varFramePtr);
 
-    if (flags != 0u) {
-      /*
-       * A proc frame
-       */
-      NsfCallStackContent *cscPtr =
-        (flags & (FRAME_IS_NSF_METHOD|FRAME_IS_NSF_CMETHOD)) ?
-        ((NsfCallStackContent *)Tcl_CallFrame_clientData(varFramePtr)) : NULL;
-
-      if (cscPtr != NULL) {
+      if (flags != 0u) {
         /*
-         * An NSF method frame.
+         * A proc frame
          */
-        if ((cscPtr->flags & (NSF_CSC_CALL_IS_NEXT|NSF_CSC_CALL_IS_ENSEMBLE))
-            || (cscPtr->frameType & NSF_CSC_TYPE_INACTIVE)) {
-          continue;
-        }
-      }
+        NsfCallStackContent *cscPtr =
+          (flags & (FRAME_IS_NSF_METHOD|FRAME_IS_NSF_CMETHOD)) ?
+          ((NsfCallStackContent *)Tcl_CallFrame_clientData(varFramePtr)) : NULL;
 
-      if (offset != 0) {
-        offset--;
-      } else if (Tcl_CallFrame_level(varFramePtr) < lvl) {
-        if (callingProcFramePtrPtr != NULL) {
-          *callingProcFramePtrPtr = varFramePtr;
+        if ((cscPtr != NULL)
+            && ((cscPtr->flags & (NSF_CSC_CALL_IS_NEXT|NSF_CSC_CALL_IS_ENSEMBLE))
+                || (cscPtr->frameType & NSF_CSC_TYPE_INACTIVE))
+            ) {
+          /*
+           * Skip NSF method frames, which are next calls, ensembles or inactive
+           */
+        } else {
+
+          if (offset != 0) {
+            offset--;
+          } else if (Tcl_CallFrame_level(varFramePtr) < lvl) {
+            if (callingProcFramePtrPtr != NULL) {
+              *callingProcFramePtrPtr = varFramePtr;
+            }
+            return cscPtr;
+          }
         }
-        return cscPtr;
+      } else if (callingFramePtrPtr != NULL
+                 && *callingFramePtrPtr == NULL
+                 && Tcl_CallFrame_level(varFramePtr) < lvl
+                 ) {
+        *callingFramePtrPtr = varFramePtr;
       }
+      /* 
+       * Continue in loop.
+       */
+      varFramePtr = Tcl_CallFrame_callerVarPtr(varFramePtr);
+      
+    } while (likely(varFramePtr != NULL));
 
-    } else if (callingFramePtrPtr != NULL &&
-               *callingFramePtrPtr == NULL &&
-               Tcl_CallFrame_level(varFramePtr) < lvl) {
-      *callingFramePtrPtr = varFramePtr;
+    if (callingProcFramePtrPtr != NULL) {
+      *callingProcFramePtrPtr = NULL;
     }
   }
-
-  if (callingProcFramePtrPtr != NULL) {
-    *callingProcFramePtrPtr = NULL;
-  }
   return NULL;
 }