Unicode support in C++0x

Question

I'm trying to use new unicode characters in C++0x. So I wrote sample code:

#include <fstream>
#include <string>
int main()
{
    std::u32string str = U"Hello World";

    std::basic_ofstream<char32_t> fout("output.txt");

    fout<<str;  
    return 0;
}

But after executing this program I'm getting empty output.txt file. So why it's not printing Hello World?

Also is there something like a cout and cin already defined for these types, or stdin and stdout doesn't support Unicode?

Edit: I'm using g++ and Linux.

EDIT:АТТЕNTION. I have discovered, that standard committee dismissed Unicode streams from C++0x. So previously accepted answer is not correct anymore. For more information see my answer!

Answer 1

Unicode string literals support began in GCC 4.5. Maybe that's the problem.

[edit]

After some digging I've found that streams for this new unicode literals are described in N2035 and it was included in a draft of the standard. According to this document you need u32ofstream to output you string but this class is absent in GCC 4.5 C++0x library.

As a workaround you can use ordinary fstream:

std::ofstream fout2("output2.txt", std::ios::out | std::ios::binary);
fout2.write((const char *)str.c_str(), str.size() * 4);

This way I've output your string in UTF-32LE on my Intel machine (which is little-endian).

[edit]

I was a little bit wrong about the status of u32ofstream: according to the latest draft on the The C++ Standards Committee's web site you have to use std::basic_ofstream<char32_t> as you did. This class would use codecvt<char32_t,char,typename traits::state_type> class (see end of §27.9.1.1) which has to be implemented in the standard library (search codecvt<char32_t in the document), but it's not available in GCC 4.5.