Looks like it’s mostly C, and not great C at that… In my humble opinion, this is a scary looking project.
This codebase just smells of rot all over.
Large companies like MS often have codebases that are so ancient (e.g. HRESULTs and IF_ERR_GOTO type macros everywhere), they only get modernized very gradually if at all.
Most of the stuff I see in the wild could be considered what I call C+, basically MFC style with plenty of C love.
While Microsoft has the excuse for older code bases, stuff like WRL and C++/WinRT also has its share of not only following what is preached regarding C++ Core Guidelines love.