AC_DEFUN([gl_SOCKET_FAMILIES],
[
AC_MSG_CHECKING(for IPv4 sockets)
AC_CACHE_VAL(gl_cv_socket_ipv4,
[AC_TRY_COMPILE([[int x = AF_INET; struct in_addr y; struct sockaddr_in z;],
gl_cv_socket_ipv4=yes, gl_cv_socket_ipv4=no)])
AC_MSG_RESULT($gl_cv_socket_ipv4)
if test $gl_cv_socket_ipv4 = yes; then
AC_DEFINE(HAVE_IPV4, 1, [Define to 1 if <sys/socket.h> defines AF_INET.])
fi
AC_MSG_CHECKING(for IPv6 sockets)
AC_CACHE_VAL(gl_cv_socket_ipv6,
[AC_TRY_COMPILE([[int x = AF_INET6; struct in6_addr y; struct sockaddr_in6 z;],
gl_cv_socket_ipv6=yes, gl_cv_socket_ipv6=no)])
AC_MSG_RESULT($gl_cv_socket_ipv6)
if test $gl_cv_socket_ipv6 = yes; then
AC_DEFINE(HAVE_IPV6, 1, [Define to 1 if <sys/socket.h> defines AF_INET6.])
fi
])