Index: generic/nsfStack.c
===================================================================
diff -u -r558d6c0bf34ca8204111154abca95ac474148fd3 -r56771aadda62cc84f8631070e54c87e9f2e26c8b
--- generic/nsfStack.c	(.../nsfStack.c)	(revision 558d6c0bf34ca8204111154abca95ac474148fd3)
+++ generic/nsfStack.c	(.../nsfStack.c)	(revision 56771aadda62cc84f8631070e54c87e9f2e26c8b)
@@ -51,21 +51,21 @@
   nonnull(1);
 
 static Tcl_CallFrame* CallStackGetActiveProcFrame(Tcl_CallFrame *framePtr)
-  nonnull(1);
+  nonnull(1) pure;
 
 NSF_INLINE static NsfObject* GetSelfObj2(const Tcl_Interp *UNUSED(interp), Tcl_CallFrame *framePtr)
-  nonnull(2);
+  nonnull(2) pure;
 
 static Tcl_CallFrame* CallStackGetTclFrame(const Tcl_Interp *interp,
                                            Tcl_CallFrame *varFramePtr,
                                            int skip)
-  nonnull(1);
+  nonnull(1) pure;
 
 static NsfCallStackContent* CallStackGetTopFrame(const Tcl_Interp *interp, Tcl_CallFrame **framePtrPtr)
   nonnull(1);
 
 NSF_INLINE static NsfCallStackContent* CallStackGetTopFrame0(const Tcl_Interp *interp)
-  nonnull(1);
+  nonnull(1) pure;
 
 static NsfCallStackContent* NsfCallStackFindLastInvocation(const Tcl_Interp *interp,
                                                            int offset, Tcl_CallFrame **framePtrPtr)
@@ -82,7 +82,7 @@
   nonnull(1) nonnull(2);
 
 static NsfCallStackContent* CallStackFindActiveFilter(const Tcl_Interp *interp)
-  nonnull(1);
+  nonnull(1) pure;
 
 static NsfCallStackContent* CallStackFindEnsembleCsc(const Tcl_CallFrame *framePtr, Tcl_CallFrame **framePtrPtr)
   nonnull(1) nonnull(2);
@@ -770,7 +770,7 @@
  */
 static NsfCallStackContent *
 CallStackFindActiveFilter(const Tcl_Interp *interp) {
-  register Tcl_CallFrame *varFramePtr = (Tcl_CallFrame *)Tcl_Interp_varFramePtr(interp);
+  register const Tcl_CallFrame *varFramePtr = (Tcl_CallFrame *)Tcl_Interp_varFramePtr(interp);
 
   nonnull_assert(interp != NULL);