std::string

Perhaps std::string is the most commonly used class in the C++ standard template library. Rice treats std::string’s as Builtin types, which means strings are copied between C++ and Ruby. Thus, if you pass a std::string to Ruby and modify it in Ruby, C++ will not see the changes (and vice versa).

Unlike Ruby, C++ has very little support for encodings. Thus it is a guessing game to correctly translate strings between C++ and Ruby and its up to you to get it right.

When Rice converts a std::string to Ruby it is assumed to have the encoding specified by Encoding.default_external. That is likely to be UTF-8 on Windows while on Linux and MacOS it is based on the operating system locale. If no external encoding is specified, the converted string will have an encoding ASCII-8BIT which is Ruby’s way of saying it has no encoding at all. If the encoding is incorrect, then you need to fix it in Ruby by calling String#force_encoding.

In contrast, when Rice converts a Ruby string to a std::string it simply passes the underlying char buffer to std::string for copying. Thus it is once again up to you to make sure the encoding is correctly set in Ruby before passing the string to C++.

Note that Rice does not support std::wstring.