| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Gavin Flower <GavinFlower(at)archidevsys(dot)co(dot)nz> |
| Cc: | pgsql-hackers(at)lists(dot)postgresql(dot)org |
| Subject: | Re: Using POPCNT and other advanced bit manipulation instructions |
| Date: | 2019-02-14 05:46:42 |
| Message-ID: | 17612.1550123202@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Gavin Flower <GavinFlower(at)archidevsys(dot)co(dot)nz> writes:
> From my memory of reading of K&R many moons ago, it said that C only
> guarantees that the lengths are such that
> byte <= half word <= word <= long
Indeed.
> But I don't recall ever seeing a long less than 32 bits!
I'm not sure offhand what C89 said, but C99 requires "short" to be
at least 16 bits, "long" to be at least 32 bits, and "long long"
to be at least 64; see the minimum allowed values for SHRT_MAX etc.
C99 does permit "int" to be only 16 bits, but Postgres doesn't
pretend to work on such an architecture, and nobody's made one
since the (early?) 90s.
regards, tom lane
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