AppPkg/Applications/Python/Python-2.7.2/Lib/test/crashers/mutation_inside_cyclegc.py

   1
   2 # The cycle GC collector can be executed when any GC-tracked object is
   3 # allocated, e.g. during a call to PyList_New(), PyDict_New(), ...
   4 # Moreover, it can invoke arbitrary Python code via a weakref callback.
   5 # This means that there are many places in the source where an arbitrary
   6 # mutation could unexpectedly occur.
   7
   8 # The example below shows list_slice() not expecting the call to
   9 # PyList_New to mutate the input list.  (Of course there are many
  10 # more examples like this one.)
  11
  12
  13 import weakref
  14
  15 class A(object):
  16     pass
  17
  18 def callback(x):
  19     del lst[:]
  20
  21
  22 keepalive = []
  23
  24 for i in range(100):
  25     lst = [str(i)]
  26     a = A()
  27     a.cycle = a
  28     keepalive.append(weakref.ref(a, callback))
  29     del a
  30     while lst:
  31         keepalive.append(lst[:])