[issue1621] Do not assume signed integer overflow behavior

[Martin Panter]

Martin Panter added the comment:

The check in ins1() was originally added in revision b9002da46f69. I presume it references the Python-dev thread “can this overflow (list insertion)?” <20000812145155.A7629 at ActiveState.com>, <https://marc.info/?l=python-dev&m=107666472818169>. At that time, ob_size was an int, so overflow checking was definitely needed. Later, revision 7fdc639bc5b4 changed ob_size to Py_ssize_t, and then revision 606818c33e50 updated the overflow check from INT_MAX to PY_SSIZE_T_MAX.

BTW I made a small mistake in my previous message. The worst case would be extending a list with itself. But I think the conclusion is still the same.

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<http://bugs.python.org/issue1621>
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