On 2015-09-16 15:57:04 -0400, Tom Lane 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".
According to C that's undefined behaviour. So in the extreme sense that could mean that the instruction could trigger a SIGBUS or something. > 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. But in other places We do overflow checks, so I don't think that'd be reversal of a general approach. Greetings, Andres Freund -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
