https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104461
Xi Ruoyao <xry111 at mengyan1223 dot wang> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |jwakely.gcc at gmail dot com, | |xry111 at mengyan1223 dot wang --- Comment #1 from Xi Ruoyao <xry111 at mengyan1223 dot wang> --- It's because the paper (https://wg21.link/p1184) explicitly says "an ipv6 domain socket & port", I think. It's not clear if AI_V4MAPPED addresses are allowed. The problem is there is no "elegent" way for a distro maintainer to ensure an IPv6 address for localhost is available on Linux/GNU. If /etc/nsswitch.conf contains hosts: files dns (this is the default of Glibc and used by many distros), and /etc/hosts contains 127.0.0.1 localhost ::1 localhost By default Glibc will ignore "::1" for localhost, unless "multi on" is specified in /etc/host.conf. But Glibc doc explicitly says it may cause a performance issue (see man host.conf). On systems using systemd, the distro can specify nss_myhostname in /etc/nsswitch.conf, but it does not exist on non-systemd distros.