Linux releases between July 2008 and May 2009 (versions 2.6.27 to 2.6.29).
@item
+This function returns @code{EMFILE} instead of @code{EBADF} for
+extremely large targets, which interferes with using
+@code{dup2(fd,fd)==fd)} as the minimal @code{EBADF} filter:
+FreeBSD 6.1, Cygwin 1.5.
+
+@item
This function is missing on some older platforms.
@end itemize