Likely GMP bug
nisse at lysator.liu.se
Fri May 25 12:10:54 UTC 2018
Dennis Clarke <dclarke at blastwave.org> writes:
> gcd_1.c:187:13: runtime error: shift exponent 32 is too large for
> 32-bit type 'long unsigned int'
> FAIL t-cmp_ui (exit status: 1)
And code is essentially
count_trailing_zeros (c, t);
ulimb >>= (c + 1);
The intention is to shift right to get rid of both trailing zero bits,
and the redundant least significant one bit.
That fails with undefined behavior if by chance t == 2^31, so that c ==
I don't see how that can happen, though, since ulimb, vlimb < 2^31
through out the loop, and t = (ulimb - vlimb) mod 2^32.
And I also wonder why USE_ZEROTAB is set to 0 here.
Niels Möller. PGP-encrypted email is preferred. Keyid 368C6677.
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