[New-bugs-announce] [issue23999] Undefined behavior in dtoa.c (rshift 32 of 32bit data type)

[Christian Heimes]

New submission from Christian Heimes:

Coverity has found undefined behavior in dtoa.c:d2b(). lo0bits() can return 32 which z >>= 32, where z is an uint32. I've talked to doku at PyCon. He suggested to update dtoa.c to a more recent version. Our copy is based on a version from 2001. There are more modern versions available, e.g. https://searchcode.com/codesearch/view/52748288/ from 2006.

CID 1202735 (#1 of 1): Bad bit shift operation (BAD_SHIFT)
large_shift: In expression z >>= k, right shifting by more than 31 bits has undefined behavior. The shift amount, k, is 32.

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messages: 241464
nosy: christian.heimes, doko, eric.smith, mark.dickinson, serhiy.storchaka
priority: normal
severity: normal
stage: needs patch
status: open
title: Undefined behavior in dtoa.c (rshift 32 of 32bit data type)
type: behavior
versions: Python 2.7, Python 3.3, Python 3.4, Python 3.5

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue23999>
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