From: Tom Lane <tgl@sss.pgh.pa.us>
To: Mark Dilger <mark.dilger@enterprisedb.com>
cc: Robert Haas <robertmhaas@gmail.com>, Peter Geoghegan <pg@bowt.ie>,
        "Andrey M. Borodin" <x4mmm@yandex-team.ru>,
        Stephen Frost <sfrost@snowman.net>,
        Michael Paquier <michael@paquier.xyz>, Amul Sul <sulamul@gmail.com>,
        Dilip Kumar <dilipbalaut@gmail.com>,
        Andres Freund <andres@anarazel.de>,
        PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: new heapcheck contrib module
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Comments: In-reply-to Mark Dilger <mark.dilger@enterprisedb.com>
	message dated "Fri, 23 Oct 2020 13:52:18 -0700"
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Date: Fri, 23 Oct 2020 17:20:59 -0400
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Mark Dilger <mark.dilger@enterprisedb.com> writes:
>> On Oct 23, 2020, at 11:51 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> I do not have 64-bit big-endian hardware to play with unfortunately.
>> But what I suspect is happening here is less about endianness and
>> more about alignment pickiness; or maybe we were unlucky enough to
>> index off the end of the shmem segment.

> You certainly appear to be right about that.  I've added the extra check=
s, and extended the regression test to include them.  Patch attached.

Meanwhile, I've replicated the SIGBUS problem on gaur's host, so
that's definitely what's happening.

(Although PPC is also alignment-picky on the hardware level, I believe
that both macOS and Linux try to mask that by having kernel trap handlers
execute unaligned accesses, leaving only a nasty performance loss behind.
That's why I failed to see this effect when checking your previous patch
on an old Apple box.  We likely won't see it in the buildfarm either,
unless maybe on Noah's AIX menagerie.)

I'll check this patch on gaur and push it if it's clean.

			regards, tom lane