I haven't looked at the patches, but couldn't we have the IPv6 code be #ifdef'ed out, so that those who care about IPv6 can periodically test it while the various OS-level libraries are ramped up over the next months/years, but w/o disturbing the 'current' builds?
Not if we are going to introduce itojun's patch. In that patch, the IPv6 code *is* actually ifdef'ed out. It is getaddrinfo/getnameinfo that gives problems, which isn't IPv6 specific at all.
The problem is that the library patches (httplib, ftplib, etc) do use getaddrinfo to find out how to contact a remote system, which is the right thing to do IMO. So even if the IPv6 support can be activated only if desired, getaddrinfo absolutely has to work.
So the only question then is where we get an implementation of these functions if the system doesn't provide one. itojun has suggested the WIDE libraries; since they apparently don't compile on Windows, I've suggested the MS TP emulation. If the latter is not acceptable, we either have to fix the WIDE implementation to work on Windows also;
As for the problems Mark reported: I think they can get fixed.