Hi all,

I am troubleshooting a locale related issue of our C++ software when building with musl. With some efforts I narrowed our problem down to the inability of setting a UTF-8 locale in C++ standard library.

The following C code prints UTF-8 characters correctly:
#include <ncurses.h>
#include <langinfo.h>
#include <locale.h>

int main()
{
    setlocale(LC_ALL, "");
    initscr();
    printw("LC_ALL: %s\n", setlocale(LC_ALL, NULL));
    printw("CODESET: %s\n", nl_langinfo(CODESET));
    printw("Hello, world!\n");
    printw("你好，世界!\n");
    refresh();
    getch();
    endwin();
    return 0;
}

Giving the output of
LC_ALL: C.UTF-8;C;C;C;C;C
CODESET: UTF-8
Hello, world!
你好，世界!

However, the following C++ code does not work (our software uses std::locale in C++ standard library for locale related stuff):
#include <langinfo.h>
#include <locale.h>
#include <locale>
using namespace std;
int main()
{
    std::locale::global(locale(""));
    initscr();
    printw("LC_ALL: %s\n", setlocale(LC_ALL, NULL));
    printw("C++ locale: %s\n", locale().name().c_str());
    printw("CODESET: %s\n", nl_langinfo(CODESET));
    printw("Hello, world!\n");
    printw("你好，世界!\n");
    refresh();
    getch();
    endwin();
    return 0;
}

Giving a corrupted output:
LC_ALL: C
C++ locale: C
CODESET: ASCII
Hello, world!
你好?~L?~V?~U~L!

Seems only ASCII C locale is available in C++. If I run the above C++ code with LANG="C.UTF-8", an exception is thrown and the program is aborted:
terminate called after throwing an instance of 'std::runtime_error'
  what():  locale::facet::_S_create_c_locale name not valid
Aborted

I also tried LANG="UTF-8”, LANG="en_US.UTF-8" but none of those works. Only LANG="C" could make the program run but then only ASCII characters are supported.

My question is that is there a way to make locale in C++ standard library work with musl? Or had I done anything wrong with it?

Regards,
Brett