You usually can in any situation where you would be porting the library in question. I'm going to have a hard time if I want to make OpenGL calls work on my old

You usually can in any situation where you would be porting the library in question. I'm going to have a hard time if I want to make OpenGL calls work on my old Z80 micros... but why would I want to? Anywhere I would want to port a library that uses epoll it is trivial to re-implement the functionality using poll(2)/select(2) or even simply setting O_NONBLOCK and busy-waiting while manually polling read(2). Other platforms may have other non-standard features that are full or partial replacements. Performance may not be the same, but that's a common problem when porting software. I'm sure it's possible to find various pathological cases where this is difficult. In the common cases, proper abstraction is worth it simply for the complexity and maintenance costs. edit: None of this should be taken as a recommendation for the epoll interface. vezzy-fnord is right - there are much better solutions available.