But did you? My FreeBSD knowledge is quite outdated, I believe the last version I worked with is 7, but I believe at some point, it was possible to compile C++ kernel modules for FreeBSD. This time I can not find the proof, but plus to that post I also found links like

https://lists.freebsd.org/pipermail/freebsd-hackers/2009-Feb... https://lists.freebsd.org/pipermail/freebsd-hackers/2006-Jul...

The last one mentions: "There's actually a fair amount of experience with people doing C++ in FreeBSD kernels. People have been doing things with it for about 8 years now."