Using select but not kqueue on macOS

[dsh0416]

macOS should support kqueue in libev, but it seems to use select when using the selector.
I've checked extconf.rb, it doesn't help even if I disabled the -DEV_USE_SELECT in compile flags.

2.4.0 :001 > require 'nio'
 => true
2.4.0 :002 > NIO::Selector.new.backend
 => :select

[tarcieri]

Please see the libev documentation re: OS X:

http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#OS_X_AND_DARWIN_BUGS

[tarcieri]

That said, I really don't think switching the defaults on OS X makes sense: OS X is most likely going to be used as a development platform, in which case I'd rather maximize having it work "as if it were Linux" than break (by default) with OS X errata as soon as someone tries to select on a non-socket type. The only advantage would be handling a larger number of connections, but are you really handling hundreds/thousands of concurrent connections on OS X?

[dsh0416]

I was just testing concurrency on macOS, and it seems buggy, so that I opened this issue. Very few people may use it in "production environment", which makes sense that the backend problem doesn't matter.