From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alexander Korotkov <aekorotkov@gmail.com>
Cc: Heikki Linnakangas <hlinnaka@iki.fi>
Cc: Alexander Korotkov <akorotkov@postgresql.org>
Cc: pgsql-hackers@lists.postgresql.org
Subject: Re: Detecting pointer misalignment (was Re: pgsql: Implementation of subscripting for jsonb)
Date: Sun, 07 Feb 2021 20:20:00 -0500
Message-ID: <477102.1612747200@sss.pgh.pa.us> (raw)
In-Reply-To: <475514.1612745257@sss.pgh.pa.us>
References: <E1l6Jjn-0000kp-75@gemulon.postgresql.org>
<37bb56a0-391d-759d-771b-9c1d8c15a84b@iki.fi>
<3293925.1612163110@sss.pgh.pa.us>
<CAPpHfdsne3=T=fMNU45PtxdhSL_J2PjLTeS8rwKnJzUR4YNd4w@mail.gmail.com>
<CAPpHfdu8Jh0tySa50Zhkyg6gMvi2pQFdHAMiF+UkZNqsDLwTQw@mail.gmail.com>
<475514.1612745257@sss.pgh.pa.us>
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
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Cc: tgl@sss.pgh.pa.us, aekorotkov@gmail.com, hlinnaka@iki.fi, akorotkov@postgresql.org, pgsql-hackers@lists.postgresql.org
Subject: Re: Detecting pointer misalignment (was Re: pgsql: Implementation of subscripting for jsonb)
In-Reply-To: <477102.1612747200@sss.pgh.pa.us>
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