+@item
+This header file does not define @code{struct timeval} on some platforms:
+OSF/1 4.0.
+@item
+This header file is not self-contained --- it requires @code{<string.h>}
+before @code{FD_ZERO} can be used --- on some platforms:
+AIX 7.1, Solaris 11 2011-11.