+Portability problems not fixed by Gnulib:
+@itemize
+@item
+Some platforms lack the ability to change the timestamps of a file
+descriptor, so the replacement can fail with @code{ENOSYS}; the gnulib
+module @samp{utimens} provides a more reliable interface @code{fdutimens}.
+@item
+The mere act of using @code{stat} modifies the access time of
+directories on some platforms, so @code{utimensat} can only
+effectively change directory modification time:
+Cygwin 1.5.x.
+@end itemize