How to use Unicode range in C++ regex

I have to use unicode range in a regex in C++. Basically what I need is to have a regex to accept all valid unicode characters..I just tried with the test expression and facing some issues with it.

std::regex reg("^[\\u0080-\\uDB7Fa-z0-9!#$%&'*+/=?^_`{|}~-]+$");

Is the issue is with \\u?

This should work fine but you need to use std::wregex and std::wsmatch. You will need to convert the source string and regular expression to wide character unicode (UTF-32 on Linux, UTF-16(ish) on Windows) to make it work.

This works for me where source text is UTF-8:

inline std::wstring from_utf8(const std::string& utf8)
{
    // code to convert from utf8 to utf32/utf16
}

inline std::string to_utf8(const std::wstring& ws)
{
    // code to convert from utf32/utf16 to utf8
}

int main()
{
    std::string test = "john.doe@神谕.com"; // utf8
    std::string expr = "[\\u0080-\\uDB7F]+"; // utf8

    std::wstring wtest = from_utf8(test);
    std::wstring wexpr = from_utf8(expr);

    std::wregex we(wexpr);
    std::wsmatch wm;
    if(std::regex_search(wtest, wm, we))
    {
        std::cout << to_utf8(wm.str(0)) << '\n';
    }
}

Output:

神谕

Note: If you need a UTF conversion library I used THIS ONE in the example above.

Edit: Or, you could use the functions given in this answer:

Any good solutions for C++ string code point and code unit?