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 "Thu, 22 Oct 2020 14:10:55 -0700"
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Date: Thu, 22 Oct 2020 17:23:19 -0400
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Mark Dilger <mark.dilger@enterprisedb.com> writes:
> Yeah, I'm already looking at that.  The logic in verify_heapam skips ove=
r line pointers that are unused or dead, and the test is reporting zero co=
rruption (and complaining about that), so it's probably not going to help =
to overwrite all the line pointers with this particular bit pattern any mo=
re than to just overwrite the first one, as it would just skip them all.

> I think the test should overwrite the line pointers with a variety of di=
fferent bit patterns, or one calculated to work on all platforms.  I'll ha=
ve to write that up.

What we need here is to produce the same test results on either
endianness.  So probably the thing to do is apply the equivalent
of ntohl() to produce a string that looks right for either host
endianness.  As a separate matter, you'd want to test corruption
producing any of the four flag bitpatterns, probably.

It says here you can use Perl's pack/unpack functions to get
the equivalent of ntohl(), but I've not troubled to work out how.

			regards, tom lane