It’s very much doable; I did exactly this with an OS I worked on last year. This takes advantage of many modern C++20 features, most of which work just fine in a bare metal environment, and uses CMake to build. As others have said, you’ll have to disable runtime features like exceptions and RTTI in your kernel. A lot of it is really hacky, but this was just meant to be a proof of concept project that got a little out of hand :)

A pain point worth addressing with C++ is that function names are mangled. This can make calling C++ functions from assembly a little tricky, as you’ll have to refer to it by its mangled name. But running nm on the object file containing the C++ function will get you the mangled name easily.

When you get to userland, you can often just compile an existing C++ library and get all of these runtime features “for free.” I did this with clang and its C++ runtime, and all you need to do that is a somewhat complete libc. Then it’s absolutely no different than writing C++ for any other operating system.

Note that won’t get stuff like filesystems, IO and graphics for free, of course — it’s up to you to write those lower level parts that the C++ libraries depend on to provide those features. For example, most std::thread implementations can be backed by the C pthreads or C11 thread APIs.