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.