From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Peter Eisentraut <peter_e(at)gmx(dot)net>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: [PATCH] unified frontend support for pg_malloc et al and palloc/pfree mulation (was xlogreader-v4) |
Date: | 2013-01-11 21:02:07 |
Message-ID: | 20130111210207.GB26751@awork2.anarazel.de |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
On 2013-01-11 15:52:19 -0500, Tom Lane wrote:
> Andres Freund <andres(at)2ndquadrant(dot)com> writes:
> > On 2013-01-11 15:05:54 -0500, Tom Lane wrote:
> >> And another thing: what if the elevel argument isn't safe for multiple
> >> evaluation? No such hazard ever existed before these patches, so I'm
> >> not very comfortable with adding one. (Even if all our own code is
> >> safe, there's third-party code to worry about.)
>
> > Hm. I am not really too scared about those dangers I have to admit.
>
> I agree the scenario doesn't seem all that probable, but what scares me
> here is that if we use "__builtin_constant_p(elevel) && (elevel) >= ERROR"
> in some builds, and just "(elevel) >= ERROR" in others, then if there is
> any code with a multiple-evaluation hazard, it is only buggy in the
> latter builds. That's sufficiently nasty that I'm willing to give up
> an optimization that we never had before 9.3 anyway.
Well, why use it at all then and not just rely on
__builtin_unreachable() in any recent gcc (and llvm fwiw) and abort()
otherwise? Then the code is small for anything recent (gcc 4.4 afair)
and always consistently buggy.
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
From | Date | Subject | |
---|---|---|---|
Next Message | Joshua D. Drake | 2013-01-11 21:03:47 | LLVM / CLang / PostgreSQL |
Previous Message | Tom Lane | 2013-01-11 20:52:19 | Re: [PATCH] unified frontend support for pg_malloc et al and palloc/pfree mulation (was xlogreader-v4) |