Re: Backpatching of "Teach the regular expression functions to do case-insensitive matching"

Robert Haas <robertmhaas@gmail.com> writes:
> On the flip side, the risk of it flat-out blowing up seems pretty
> small.  For someone to invent their own version of wchar_t that uses
> something other than Unicode code points would be pretty much pure
> masochism, wouldn't it?

Well, no, that's not clear.  The C standard has pretty carefully avoided
constraining the wchar_t representation, so implementors are free to do
whatever is most convenient from the standpoint of their library routines.
I could easily see somebody deciding to do something that wasn't quite
Unicode because it let him re-use lookup tables designed for some other
encoding, or some such.

Now it's also perfectly possible, maybe even likely, that nobody's done
that on any platform we care about.  But I don't believe we know that
with any degree of certainty.  We definitely have not made any effort to
establish whether it's true --- for example, we have no regression tests
that address the point.  (I think that collate.linux.utf8 touches on it,
but we're a long way from being able to run that on non-glibc
platforms...)
        regards, tom lane