When writing an IPv6 enabled server, using the AI_V4MAPPED flag to get IPv4 addresses as IPv6 mapped addresses also somehow requires the AI_ALL flag or it doesn't work.
This conflicts the manual page and also the opengroup docs.
Update: the above is on Debian GNU/Linux sid with glibc 2.7-15.
Just tested it on opensolaris and they DO provide the correct behaviour. Time for a bugreport