Comment 7 for bug 505497

Threads cannot really be said to be supported on a platform without this functionality or some replacement thereof, however... Obviously the change could just be conditioned on #-darwin, but that won't actually *fix* the problem on darwin w/threads.

Do you have any idea if there's a replacement function under a different name for Darwin?

Or, for a totally different way to fix things, it might be best to just add the set of IPPROTO_* constants to the constants list (sb-grovel already seems to do the appropriate #ifdef stuff to only import the name if it exists on the system's header file), and then just include directly in SBCL a keyword->int translation list for those constants. (I'd suggest simply exporting the constants, and making users do "sb-bsd-sockets:+ipproto-tcp+", but for backwards compatibility)...