This is a myth that seems to never die. OS kernels can and have been written in GC languages. Watch the video maybe? The whole presentation was running on a distro fully compiled with FillC.
Ok, I stand corrected: only the kernel userland was compiled with Fil-C.
However, I don't see why the full Linux kernel could not be compiled with Fil-C. It would be nice if Fil himself could explain what limitations there are, but the documentation does not list missing C/C++ features as far as I know, it only says it's "fanatically compatible" which I take to mean mostly everything should work?!
But to my point in general, here's a osdev.org wiki explaining how high level languages can and have been used for OS development (with the caveat that some Assembly code is required, which I believe is also true of kernels written in C): https://wiki.osdev.org/Languages
> I'm running on an OS where the entire userland is compiled with Fil-C/C++
(emphasis mine)
Looking up https://fil-c.org/pizlix , that says,
> The kernel is compiled with Yolo-C. So that you can compile the kernel, a copy of GCC is installed in /yolo/bin/gcc.
Where do you see anything saying the Linux (the kernel) can be built with Fil-C?