C++ :: Open File Named In Unicode Characters

How to open a file which its name is unicode letters ? usually :

Code:
basic_ifstream<wchar_t> src("source.txt");

Work well to read file with unicode content not filename, so that example doesn't work :

Code:
basic_ifstream<wchar_t> src(L"source.txt");

Also, I have seen some alternatives for using open function but it doesn't work as well.

Code:
basic_ifstream<wchar_t> src;
src.open(L"source.txt");

I use g++ compiler.