[issue16991] Add OrderedDict written in C

[Eric Snow]

Eric Snow added the comment:

Cool.  The following gives consistent failures at certain seed values:

  for i in `seq 1 100`; do echo $i; PYTHONHASHSEED=$i ./python -m test.regrtest -m test_basic test_configparser ; done

Through 100 I get segfaults with 7, 15, 35, 37, 39, 40, 42, 47, 50, 66, 67, 85, 87, 88, and 92.  The distribution is probably essentially uniform across the full set of seeds, even if the exact pattern of failures isn't precisely uniform.  I'll try to see why those hashes are significant here.  If I can't figured it out quickly then I'll post about it on python-dev.

My hunch is that the hash randomization impacts either dict/odict resizing or dict/odict lookup (or both).  TBH, I've been pretty sure for a while that the segfault is coming out of one of those two.

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<http://bugs.python.org/issue16991>
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