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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Marina Polyakova <m.polyakova@postgrespro.ru>
Cc: Andres Freund <andres@anarazel.de>
Cc: pgsql-hackers@postgresql.org, Alvaro Herrera <alvherre@alvh.no-ip.org>
Subject: Re: master make check fails on Solaris 10
Date: Sat, 13 Jan 2018 13:10:55 -0500
Message-ID: <15299.1515867055@sss.pgh.pa.us> (raw)
In-Reply-To: <b946893927ccfd87146d8a7c9f3bbe29@postgrespro.ru>
References: <0d3a9fa264cebe1cb9966f37b7c06e86@postgrespro.ru>
	<20180111173938.jimybeayp2u5mmup@alap3.anarazel.de>
	<31a342fa6a025a8bdfc5b8b19c29d56d@postgrespro.ru>
	<fc3c1b52d2d4121cccfc13635005bbd0@postgrespro.ru>
	<1232.1515780057@sss.pgh.pa.us>
	<b946893927ccfd87146d8a7c9f3bbe29@postgrespro.ru>

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




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