+@item
+This function does not support @code{F_DUPFD_CLOEXEC} on some
+platforms:
+MacOS X 10.3, FreeBSD 6.0, NetBSD 3.0, OpenBSD 3.8, AIX 5.1, HP-UX 11,
+IRIX 6.5, OSF/1 5.1, Solaris 10, Cygwin 1.7.1, mingw, Interix 3.5,
+BeOS.
+Note that the gnulib replacement code is functional but not atomic.
+
+@item
+The @code{F_DUPFD} action of this function does not reject
+out-of-range targets properly on some platforms:
+Cygwin 1.5.x.
+
+@item
+This function is missing on some platforms:
+mingw.