Horton

Re: Detecting pointer misalignment (was Re: pgsql: Implementation of subscripting for jsonb)

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

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alexander Korotkov <aekorotkov@gmail.com>
Cc: Heikki Linnakangas <hlinnaka@iki.fi>, Alexander Korotkov <akorotkov@postgresql.org>, pgsql-hackers@lists.postgresql.org
Date: 2021-02-08T01:20:00Z
Lists: pgsql-hackers 
I wrote:
> * Both clang and gcc seem to be happy with the same spelling of the
> function attribute, which is fortunate.  However, I seriously doubt
> that bare "#ifdef __GNUC__" is going to be good enough.  At the very
> least there's going to need to be a compiler version test in there,
> and we might end up needing to get the configure script involved.

After digging in gcc's release history, it seems they invented
"-fsanitize=alignment" in GCC 5, so we can make this work for gcc
by writing

#if __GNUC__ >= 5

(the likely() macro already uses a similar approach).  Can't say
if that's close enough for clang too.

			regards, tom lane

Commits

  1. pg_attribute_no_sanitize_alignment() macro

  2. Tweak compiler version cutoff for no_sanitize("alignment") support.

  3. Implementation of subscripting for jsonb