[email protected] (Niels Möller) writes:
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 ==
31.
And ubsan complains about exactly that.
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.
The setting GMP_CHECK_RANDOMIZE=140064609456624 seems to trigger it, but
that could of course also be bugs in the compiler.
And I also wonder why USE_ZEROTAB is set to 0 here.
That might be good as count_trailing_zeros is usually fast.
--
Torbjörn
Please encrypt, key id 0xC8601622
_______________________________________________
gmp-bugs mailing list
[email protected]
https://gmplib.org/mailman/listinfo/gmp-bugs
