Horton

Re: pg_verify_checksums and -fno-strict-aliasing

Michael Paquier <michael@paquier.xyz>

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From: Michael Paquier <michael@paquier.xyz>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Fabien COELHO <coelho@cri.ensmp.fr>, Michael Banck <michael.banck@credativ.de>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2018-08-30T17:56:52Z
Lists: pgsql-hackers 
On Thu, Aug 30, 2018 at 10:39:26AM -0400, Tom Lane wrote:
> I rather suspect that this hasn't been tested on anything but Intel
> hardware, which is famously misalignment-tolerant.  The lack of any
> apparent regression test infrastructure for it isn't leaving a warm
> feeling about how much the buildfarm is testing it.
> 
> (The right fix, of course, is to malloc the work buffer rather than
> put it on the stack.)

pg_upgrade/file.c is careful about that (5afcd2a), and has a comment on
the matter, as does pg_standby.c.

Now, grepping around for "BLCKSZ]", some garbage may have accumulated?
- entrySplitPage in ginentrypage.c
- rewind_copy_file_range in file.c
- _hash_alloc_buckets in hashpage.c
- pg_prewarm.c
- blinsert.c
- pg_waldump.c
- logtape.c
--
Michael

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.