Re: Remaining dependency on setlocale()

On Wed, Aug 7, 2024 at 10:23 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Jeff Davis <pgsql(at)j-davis(dot)com> writes:
> > But there are a couple problems:
>
> > 1. I don't think it's supported on Windows.
>
> Can't help with that, but surely Windows has some thread-safe way.

It does. It's not exactly the same, instead there is a thing you can
call that puts setlocale() itself into a thread-local mode, but last
time I checked that mode was missing on MinGW so that's a bit of an
obstacle.

How far can we get by using more _l() functions? For example, [1]
shows a use of strftime() that I think can be converted to
strftime_l() so that it doesn't depend on setlocale(). Since POSIX
doesn't specify every obvious _l function, we might need to provide
any missing wrappers that save/restore thread-locally with
uselocale(). Windows doesn't have uselocale(), but it generally
doesn't need such wrappers because it does have most of the obvious
_l() functions.

> > 2. I don't see a good way to canonicalize a locale name, like in
> > check_locale(), which uses the result of setlocale().
>
> What I can tell you about that is that check_locale's expectation
> that setlocale does any useful canonicalization is mostly wishful
> thinking [1]. On a lot of platforms you just get the input string
> back again. If that's the only thing keeping us on setlocale,
> I think we could drop it. (Perhaps we should do some canonicalization
> of our own instead?)

+1

I know it does something on Windows (we know the EDB installer gives
it strings like "Language,Country" and it converts them to
"Language_Country.Encoding", see various threads about it all going
wrong), but I'm not sure it does anything we actually want to
encourage. I'm hoping we can gradually screw it down so that we only
have sane BCP 47 in the system on that OS, and I don't see why we
wouldn't just use them verbatim.

[1] https://www.postgresql.org/message-id/CA%2BhUKGJ%3Dca39Cg%3Dy%3DS89EaCYvvCF8NrZRO%3Duog-cnz0VzC6Kfg%40mail.gmail.com