Re: [PATCH] unified frontend support for pg_malloc et al and palloc/pfree mulation (was xlogreader-v4)

On 2013-01-11 16:16:58 -0500, Tom Lane wrote:
> Andres Freund <andres@2ndquadrant.com> writes:
> > On 2013-01-11 15:52:19 -0500, Tom Lane wrote:
> >> 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.
>
> Uh ... because it's *not* unreachable if elevel < ERROR.  Otherwise we'd
> just mark errfinish as __attribute((noreturn)) and be done.  Of course,
> that's a gcc-ism too.

Well, I mean with the double evaluation risk.

Greetings,

Andres Freund

-- Andres Freund                       http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training &
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