A new crasher.
diff --git a/Lib/test/crashers/mutation_inside_cyclegc.py b/Lib/test/crashers/mutation_inside_cyclegc.py
new file mode 100644
index 0000000..2b67398
--- /dev/null
+++ b/Lib/test/crashers/mutation_inside_cyclegc.py
@@ -0,0 +1,31 @@
+
+# The cycle GC collector can be executed when any GC-tracked object is
+# allocated, e.g. during a call to PyList_New(), PyDict_New(), ...
+# Moreover, it can invoke arbitrary Python code via a weakref callback.
+# This means that there are many places in the source where an arbitrary
+# mutation could unexpectedly occur.
+
+# The example below shows list_slice() not expecting the call to
+# PyList_New to mutate the input list. (Of course there are many
+# more examples like this one.)
+
+
+import weakref
+
+class A(object):
+ pass
+
+def callback(x):
+ del lst[:]
+
+
+keepalive = []
+
+for i in range(100):
+ lst = [str(i)]
+ a = A()
+ a.cycle = a
+ keepalive.append(weakref.ref(a, callback))
+ del a
+ while lst:
+ keepalive.append(lst[:])