Horton

Re: pg_verify_checksums and -fno-strict-aliasing

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Michael Paquier <michael@paquier.xyz>
Cc: Fabien COELHO <coelho@cri.ensmp.fr>, Michael Banck <michael.banck@credativ.de>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2018-09-01T19:32:10Z
Lists: pgsql-hackers 
Michael Paquier <michael@paquier.xyz> writes:
> On Fri, Aug 31, 2018 at 07:59:58PM -0400, Tom Lane wrote:
>> The others you mention could be changed, probably, but I didn't
>> bother as they didn't seem performance-critical.

> It is not really critical indeed.  There is an argument to change them
> so as other folks get used to it though.

Fair enough.  I renamed the types as suggested, changed a few more
places for consistency's sake, and pushed.

There still remain some places where palloc(BLCKSZ) or equivalent is used,
but there's no matching pfree.  In a lot of them the buffer is returned
to the caller so there's no choice.  It's likely that some are just
leaking the storage transiently and we could convert them to using a
PGAlignedBlock local variable, but I didn't bother trying to do the
analysis.

			regards, tom lane

Commits

  1. Avoid using potentially-under-aligned page buffers.

  2. Code review for pg_verify_checksums.c.

  3. Make checksum_impl.h safe to compile with -fstrict-aliasing.