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33 lines
1.1 KiB
33 lines
1.1 KiB
4 months ago
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"""
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gc.get_referrers() can be used to see objects before they are fully built.
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Note that this is only an example. There are many ways to crash Python
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by using gc.get_referrers(), as well as many extension modules (even
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when they are using perfectly documented patterns to build objects).
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Identifying and removing all places that expose to the GC a
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partially-built object is a long-term project. A patch was proposed on
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SF specifically for this example but I consider fixing just this single
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example a bit pointless (#1517042).
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A fix would include a whole-scale code review, possibly with an API
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change to decouple object creation and GC registration, and according
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fixes to the documentation for extension module writers. It's unlikely
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to happen, though. So this is currently classified as
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"gc.get_referrers() is dangerous, use only for debugging".
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"""
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import gc
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def g():
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marker = object()
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yield marker
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# now the marker is in the tuple being constructed
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[tup] = [x for x in gc.get_referrers(marker) if type(x) is tuple]
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print(tup)
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print(tup[1])
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tuple(g())
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