actually a tool we wrote that would literally cause serious problems if used on a systemd machine had one that was toggled by the configure script
but once again it was more for us than anyone else so we have no problems doing this
the majority of C that we end up writing actually doesn't end up being particularly cross platform unless we need it to actually be, which is fairly rare...
we've only actually done this like, twice in our code...
both times were because of kqueue use though. we didn't want to have to rewrite the code to use libevent or ifdeffed with epoll support, and that said the explanation was much nicer.