Marina Polyakova <m.polyakova@postgrespro.ru> writes:
> On 12-01-2018 21:00, Tom Lane wrote:
>> Hm ... so apparently, that compiler has bugs in handling nondefault
>> alignment specs. You said upthread it was gcc, but what version
>> exactly?
> This is 5.2.0:
Ugh ... protosciurus has 3.4.3, but I see that configure detects that
as *not* having __int128. Probably what's happening on your machine
is that gcc knows __int128 but generates buggy code for it when an
alignment spec is given. So that's unfortunate, but it's not really
a regression from 3.4.3.
I'm not sure there's much we can do about this. Dropping the use
of the alignment spec isn't a workable option. If there were a
simple way for configure to detect that the compiler generates bad
code for that, we could have it do so and reject use of __int128,
but it'd be up to you to come up with a workable test.
In the end this might just be an instance of the old saw about
avoiding dot-zero releases. Have you tried a newer gcc?
(Digging in their bugzilla finds quite a number of __int128 bugs
fixed in 5.4.x, though none look to be specifically about
misaligned data.)
Also, if it still happens with current gcc on that hardware,
there'd be grounds for a new bug report to them.
regards, tom lane
