I meant it's written in C++[0]. The interface is exported through standard C functions, but the header files also have the declarations guarded with "extern "C"".

Microsoft do have some sample drivers that are written in C++, e.g. https://github.com/Microsoft/Windows-driver-samples/tree/mas...

[0]: https://github.com/Microsoft/Windows-Driver-Frameworks/tree/...

It has a C API, but everything under the hood is C++. The source is actually public now: https://github.com/Microsoft/Windows-Driver-Frameworks