Localized formatting is always decimal

[mamikonyan]

Localization doesn't seem to obey the 'type' specifier:

int main() {
    const auto x = 123456789;
    std::clog << std::format("{:LX}", x) << ' ' << fmt::format("{:LX}", x);
}

yields:
75BCD15 123456789
This is using tip of trunk {fmt} and GCC 13.1.0.

[vitaut]

This is the {fmt} repository, please report issues with std::format to your standard library vendor.

[mamikonyan]

Thank you for clearing this up, but perhaps this is confusing... The bug is with {fmt}, not std::format().

[vitaut]

Missed the call to fmt::format, reopening.

[vitaut]

BTW, could you elaborate why you need localized formatting of hexadecimal numbers? What is the use case?

[mamikonyan]

Yes, of course. I work with FPGAs, and it's convenient to print out register values in hexadecimal format, separated by apostrophes:

const struct: std::numpunct<char> {
    using std::numpunct<char>::numpunct;
private:
    char do_thousands_sep() const override { return '\'';  }
    std::string do_grouping() const override { return "\4"; }
} sep4{1};

std::locale loc{std::clog.getloc(), &sep4};

int main() {
    std::clog << fmt::format("0x{:LX}\n", 123456789);
}

My understanding is that this should print: 0x75B'CD15 Both GCC and Clang do. If there is an easier way to achieve this, please let me know.

[mamikonyan]

Sorry, I forgot to pass loc into fmt::format(), and editing isn't working; but you know what I mean.

[vitaut]

This has been fixed but in general it's a misuse of the locale API and I'd recommend defining a custom formatter for a wrapper type instead.