On Wed, Sep 16, 2015 at 3:57 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Robert Haas <robertmh...@gmail.com> writes: >> On Wed, Sep 16, 2015 at 3:16 AM, Craig Ringer <cr...@2ndquadrant.com> wrote: >>> Our implementation of << is a direct wrapper around the C operator. It >>> does not check the right-hand side's value. >>> ... On x64 intel gcc linux it does a rotation but that's >>> not AFAIK guaranteed by anything, and we should probably not be >>> relying on this or exposing it at the user level. > >> I agree. > > As far as I'm concerned, what those operators mean is "whatever your > compiler makes them mean". This is hardly the only place where we expose > platform-dependent behavior --- see also locale dependencies, timezones, > floating point, yadda yadda --- and I do not find it the most compelling > place to start reversing that general approach.
No, I don't agree, in this case. You could say that int32 + int32 is platform-dependent behavior too, when it overflows. But we don't say that. This case seems more like an overflow condition than it does like platform-dependent behavior that we should just pass through. Also, I think it's worth noting that, AFAICT, our users %@#! HATE the places where we expose platform-dependent behavior. That's why people keep proposing ICU for collations, and cursing their fate when Red Hat rolls out a glibc fix that changes some collation's ordering thus leaving all their indexes "corrupted". Of course, we're not in a position to eliminate all of those platform dependencies, because it would require us to integrate with - or develop - platform-dependent libraries for all of those things. And we don't really have the bandwidth for that, or at least it's not likely the best use of our time. But all things being equal, I don't think the fact that we have platform dependencies that are hard to eliminate means we should keep around the ones that are easy to eliminate. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
