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32 lines
753 B
Python
32 lines
753 B
Python
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# The cycle GC collector can be executed when any GC-tracked object is
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# allocated, e.g. during a call to PyList_New(), PyDict_New(), ...
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# Moreover, it can invoke arbitrary Python code via a weakref callback.
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# This means that there are many places in the source where an arbitrary
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# mutation could unexpectedly occur.
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# The example below shows list_slice() not expecting the call to
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# PyList_New to mutate the input list. (Of course there are many
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# more examples like this one.)
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import weakref
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class A(object):
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pass
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def callback(x):
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del lst[:]
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keepalive = []
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for i in range(100):
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lst = [str(i)]
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a = A()
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a.cycle = a
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keepalive.append(weakref.ref(a, callback))
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del a
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while lst:
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keepalive.append(lst[:])
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