From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Andres Freund <andres(at)2ndquadrant(dot)com> |
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 20:52:19 |
Message-ID: | 16304.1357937539@sss.pgh.pa.us |
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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.
> I dislike the latter somewhat as it would mean not to give that
> information at all to msvc and others which seems a bit sad. But I don't
> feel particularly strongly.
It's not like our code isn't rather gcc-biased anyway. I'd keep the
optimization for other compilers if possible, but not at the cost of
introducing bugs that occur only on those compilers.
regards, tom lane
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