[locale] Boost.Locale cannot be used with std::regex

From: Josue Andrade Gomes (josuegomes_at_[hidden])
Date: 2021-05-24 20:29:30

It seems that Boost.Locale cannot be used with std::regex. See the code below:

#include <regex>
#include <boost/locale.hpp>

int main()
{
    try {
        boost::locale::generator gen;
        std::locale de_DE(gen("de_DE.UTF-8"));
        std::wstring in(L"Grün GRÜN grün");

        std::wregex rx;
        rx.imbue(de_DE);
        rx.assign(L"grün", std::regex::icase);

        std::wcout << std::regex_replace(in, rx, L"green") << L"\n";
    }
    catch (std::exception &e) {
        std::cout << "Exception: " << e.what() << "\n";
    }
}

Outputs:

green GRÃœN green

However this:

#include <regex>
#include <locale>

int main()
{
    try {
        std::locale de_DE("de_DE.UTF-8");
        std::wstring in(L"Grün GRÜN grün");

        std::wregex rx;
        rx.imbue(de_DE);
        rx.assign(L"grün", std::regex::icase);

        std::wcout << std::regex_replace(in, rx, L"green") << L"\n";
    }
    catch (std::exception &e) {
        std::cout << "Exception: " << e.what() << "\n";
    }
}

Correctly outputs:

green green green

Tested on Ubuntu 20.04.2. g++ 10.2, Boost.Locale built with ICU
support using vcpkg (thus static link).