C++ 标准库不支持 Unicode.char 和 wchar_t 不需要是 Unicode 编码.

The C++ standard library is not Unicode-aware. char and wchar_t are not required to be Unicode encodings.

在 Windows 上，wchar_t 是 UTF-16，但标准库中没有直接支持 UTF-8 文件名(char 数据类型在 Windows 上不是 Unicode)

On Windows, wchar_t is UTF-16, but there's no direct support for UTF-8 filenames in the standard library (the char datatype is not Unicode on Windows)

使用 MSVC(以及 Microsoft STL)，提供了一个文件流构造函数，它采用 const wchar_t* 文件名，允许您将流创建为:

With MSVC (and thus the Microsoft STL), a constructor for filestreams is provided which takes a const wchar_t* filename, allowing you to create the stream as:

wchar_t const name[] = L"filename.txt";
std::fstream file(name);

但是，C++11 标准并未指定此重载(它仅保证基于 char 的版本的存在).从版本 g++ 4.8.x 开始，它也没有出现在替代 STL 实现中，例如 GCC 的 libstdc++ for MinGW(-w64).

However, this overload is not specified by the C++11 standard (it only guarantees the presence of the char based version). It is also not present on alternative STL implementations like GCC's libstdc++ for MinGW(-w64), as of version g++ 4.8.x.

请注意，就像 Windows 上的 char 不是 UTF8，在其他操作系统上 wchar_t 可能不是 UTF16.所以总的来说，这不太可能是便携的.根据标准未定义给定 wchar_t 文件名的流，并且在 chars 中指定文件名可能很困难，因为 char 使用的编码因操作系统而异

Note that just like char on Windows is not UTF8, on other OS'es wchar_t may not be UTF16. So overall, this isn't likely to be portable. Opening a stream given a wchar_t filename isn't defined according to the standard, and specifying the filename in chars may be difficult because the encoding used by char varies between OS'es.