Add hack to prevent checkstack.py from infinitely recursing (with bad input).
diff --git a/tools/checkstack.py b/tools/checkstack.py
index 1822cc8..8463500 100755
--- a/tools/checkstack.py
+++ b/tools/checkstack.py
@@ -25,6 +25,7 @@
         return
     # Find max of all nested calls.
     max = info[0]
+    info[1] = max
     for addr, callfname, usage in info[2]:
         callinfo = funcs[callfname]
         if callinfo[1] is None: