Use C++20 formatting library for concat()?

[jtv]

We now have a string formatting library, which should be exceedingly efficient at concatenating strings for exception messages and such.

My only concern really is that I'm not sure that I'd like to have locales applied to non-string items.

[tt4g]

If we support a locale, shouldn't we use the same locale as libpq to avoid confusion?

[jtv]

@tt4g I'd prefer not to, honestly, unless and until we're ready to support translation. Otherwise, numbers in error messages would suddenly come out localised (e.g. "3,000" in some locales but "3.000" in others etc.) but the localised numbers would show up in error messages that are still in the original English.

That said, I would expect the C++ runtime system to pick up the same locale settings as the C runtime in libpq. So if you set LC_CTYPE or LC_TIME or LANGUAGE, I would expect that to affect libpq and libpqxx in the same way out of the box.

[tt4g]

I thought you wanted to localize the numeric format in error messages (you want to avoid that).
As far as I know, std::format is not affected by locale unless you specify the L option: https://en.cppreference.com/w/cpp/utility/format/spec
It is safe to use std::format for string concatenation, since it is not localized unless this option is used.

[jtv]

That's good news. Thanks @tt4g.