Re: Remaining dependency on setlocale()

On Wed, Aug 7, 2024 at 7:07 PM Thomas Munro <thomas(dot)munro(at)gmail(dot)com> wrote:
> 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.

Actually the MinGW situation might be better than that these days. I
know of three environments where we currently have to keep code
working on MinGW: build farm animal fairywren (msys2 compiler
toochain), CI's optional "Windows - Server 2019, MinGW64 - Meson"
task, and CI's "CompilerWarnings" task, in the "mingw_cross_warning"
step (which actually runs on Linux, and uses configure rather than
meson). All three environments show that they have
_configthreadlocale. So could we could simply require it on Windows?
Then it might be possible to write a replacement implementation of
uselocale() that does a two-step dance with _configthreadlocale() and
setlocale(), restoring both afterwards if they changed. That's what
ECPG open-codes already.

The NetBSD situation is more vexing. I was trying to find out if
someone is working on it and unfortunately it looks like there is a
principled stand against adding it:

https://mail-index.netbsd.org/tech-userlevel/2015/12/28/msg009546.html
https://mail-index.netbsd.org/netbsd-users/2017/02/14/msg019352.html

They're right that we really just want to use "C" in some places, and
their LC_C_LOCALE is a very useful system-provided value to be able to
pass into _l functions. It's a shame it's non-standard, because
without it you have to allocate a locale_t for "C" and keep it
somewhere to feed to _l functions...