+@item
+Under BeOS, Gnulib's @code{poll} replacement can only be called on descriptors
+created by the @code{socket} function, not on regular file descriptors.
+
+@item
+Under Windows, when passing a pipe, Gnulib's @code{poll} replacement might
+return 0 even before the timeout has passed. Programs using it with pipes can
+thus busy wait.
+
+@item
+Under HP NonStop, file descriptors other than sockets do not support
+POLLHUP; they will return a "readable" status instead.