POSIX specification:
http://www.opengroup.org/onlinepubs/9699919799/basedefs/limits.h.html
Gnulib module: gethostname
Portability problems fixed by Gnulib:
HOST_NAME_MAX macro is not defined on some platforms:
MacOS X 10.5, FreeBSD 6.0, NetBSD 5.0, OpenBSD 3.8, AIX 5.1, HP-UX 11,
IRIX 6.5, OSF/1 5.1, Solaris 11 2010-11, Cygwin 1.5.x, mingw, Interix 3.5, BeOS.
Portability problems not fixed by Gnulib: