[mark-r]

I've always been curious on how this change in 3.3 impacts the C/C++ interface. I don't really know where to look it up, and since I haven't yet had to code a C++ library for Python I've had no burning need to answer the question.

[ubernostrum]

The Python C API grew some new functions and constants which are aware of what's going on and can tell you what encoding a particular Unicode object is using, read from/write to it, etc. The pre-3.3 APIs have a lot of deprecations in favor of the new API. If you want to use new API on a Unicode string created via old API, you have to use the new PyUnicode_READY() on it first.

[masklinn]

https://www.python.org/dev/peps/pep-0393/ has details down to C API changes related to the FSR implementation.