Stackless issue python#96: limit the recursion depth of cPickle

Impose a very high recursion limit. Add one call to Py_EnterRecursiveCall()
for each stack saving. This stops an infinite recursion after using
about 170MB of memory.
(grafted from cbc9f897eac548b56ec694a3001130717810e470 and 23ee2a4b0beb)

Author: Anselm Kruis

Modules/_pickle.c

@@ -3156,8 +3156,14 @@ save(PicklerObject *self, PyObject *obj, int pers_save)
 
 #ifdef STACKLESS
     /* but we save the stack after a fixed watermark */
-    if (CSTACK_SAVE_NOW(PyThreadState_GET(), self))
-        return slp_safe_pickling((void *)&save, (PyObject *)self, obj, pers_save);
+    if (CSTACK_SAVE_NOW(PyThreadState_GET(), self)) {
+        int res;
+        if (Py_EnterRecursiveCall(" while pickling an object"))
+            return -1;
+        res = slp_safe_pickling((void *)&save, (PyObject *)self, obj, pers_save);
+        Py_LeaveRecursiveCall();
+        return res;
+    }
 #endif
     if (Py_EnterRecursiveCall(" while pickling an object"))
         return -1;

Stackless/changelog.txt

@@ -1,15 +1,20 @@
 Stackless-Python News
 +++++++++++++++++++++
 
-This file documents changes to the Stackless extension of C-Python.
+This file documents user visible changes to the Stackless extension of C-Python.
 For other changes see Misc/NEWS.
 
-
 What's New in Stackless 3.X.X?
 ==============================
 
 *Release date: 20XX-XX-XX*
 
+- https://bitbucket.org/stackless-dev/stackless/issues/96
+  Impose a very high limit on the recursion depth of cPickle.
+  Previously an infinite recursion could eat up all you memory
+  and finally crash Stackless. No the recursion stops after using
+  about 170MB (32bit) / 300MB (64bit) of memory.
+
 - https://bitbucket.org/stackless-dev/stackless/issues/93
   Unify tasklet.kill(), tasklet.throw() and tasklet.raise_exception().
   They now behave almost identically. This affects the error handling in some