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PyObject.GetHashCode overflow bug #676

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GSPP opened this issue May 26, 2018 · 4 comments
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PyObject.GetHashCode overflow bug #676

GSPP opened this issue May 26, 2018 · 4 comments

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@GSPP
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GSPP commented May 26, 2018

PyObject.GetHashCode() can throw an OverflowException because IntPtr.ToInt32() does throw. See

pythonnet/src/runtime/pyobject.cs

Line 912 in b8cb6c4

return Runtime.PyObject_Hash(obj).ToInt32();
. I suggest fixing this by xoring the high and low parts of that IntPtr together. Like this:

var ulongVal = (ulong)ptr;
return (int)((uint)ulongVal ^ (uint)(ulongVal >> 32));

This happened to me when inserting into a dictionary using tensorflow objects as keys:

new Dictionary<dynamic, dynamic>() { { x, 1.0 }, { y, 1.0 }, }

Environment

  • Pythonnet version: 2.3
  • Python version: 3.5
  • Operating System: Windows 7
@filmor
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filmor commented May 26, 2018

Yes, please, can you prepare a PR for this?

@GSPP
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GSPP commented May 26, 2018

I don't have the project set up. I can submit a blind untested PR if that helps.

@filmor
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filmor commented May 26, 2018

Sure, go ahead. It's anyways tricky to write tests for this as you need both a 64bit system and reliably force allocation above 2^32 for this patch to make a difference.

@GSPP GSPP mentioned this issue May 27, 2018
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@GSPP
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GSPP commented May 27, 2018

The PR is there. Some build stuff failed. I have no idea what it means. I compiled and ran tests locally.

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@filmor @GSPP