| From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
|---|---|
| To: | Peter Geoghegan <pg(at)heroku(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andreas Karlsson <andreas(at)proxel(dot)se>, Petr Jelinek <petr(at)2ndquadrant(dot)com>, David Rowley <dgrowleyml(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Using 128-bit integers for sum, avg and statistics aggregates |
| Date: | 2015-03-18 22:16:14 |
| Message-ID: | 20150318221614.GB26995@alap3.anarazel.de |
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| Lists: | pgsql-hackers |
On 2015-03-18 14:00:51 -0700, Peter Geoghegan wrote:
> Anyway, I think that it's not quite the same. For one thing, we're
> talking about a GCC extension, not a type described by C99. We don't
> care about snprintf support, for example.
I don't see that that has any consequence wrt Andreas' test.
> For another, Andreas has chosen to lump together __int128 and unsigned
> __int128 into one test, where the latter really doesn't receive
> coverage.
On my urging actually. It's pretty darn unlikely that only one variant
will work. Useless configure tests just cost time. We're testing a gcc
extension here, as you point out, it'll not just stop working for
unsigned vs signed.
The reason we need a link test (vs just a compile test) is that gcc
links to helper functions to do math - even if they're not present on
the target platform. Compiling will succeed, but linking won't.
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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