Re: Odd 9.4, 9.3 buildfarm failure on s390x

Mark Wong <mark@2ndQuadrant.com> writes:
>                   a                   |                  a                   |  uuid_cmp
> --------------------------------------+--------------------------------------+-------------
>  11111111-1111-1111-1111-111111111111 | 11111111-1111-1111-1111-111111111111 |           0
>  11111111-1111-1111-1111-111111111111 | 22222222-2222-2222-2222-222222222222 | -2147483648
>  11111111-1111-1111-1111-111111111111 | 3f3e3c3b-3a30-3938-3736-353433a2313e | -2147483648
>  22222222-2222-2222-2222-222222222222 | 11111111-1111-1111-1111-111111111111 |           1
>  22222222-2222-2222-2222-222222222222 | 22222222-2222-2222-2222-222222222222 |           0
>  22222222-2222-2222-2222-222222222222 | 3f3e3c3b-3a30-3938-3736-353433a2313e | -2147483648
>  3f3e3c3b-3a30-3938-3736-353433a2313e | 11111111-1111-1111-1111-111111111111 |           1
>  3f3e3c3b-3a30-3938-3736-353433a2313e | 22222222-2222-2222-2222-222222222222 |           1
>  3f3e3c3b-3a30-3938-3736-353433a2313e | 3f3e3c3b-3a30-3938-3736-353433a2313e |           0
> (9 rows)


Oooh ... apparently, on that platform, memcmp() is willing to produce
INT_MIN in some cases.  That's not a safe value for a sort comparator
to produce --- we explicitly say that somewhere, IIRC.  I think we
implement DESC by negating the comparator's result, which explains
why only the DESC case fails.

            regards, tom lane