@code{ENOSYS} on some platforms:
Linux kernel 2.6.21.
@item
+This function fails with @code{ENOSYS} if passed the flag
+@code{AT_SYMLINK_NOFOLLOW} on a regular file:
+Linux kernel 2.6.22.
+@item
When using @code{UTIME_OMIT} or @code{UTIME_NOW}, some systems require
the @code{tv_sec} argument to be 0, and don't necessarily handle all
file permissions in the manner required by POSIX:
Linux kernel 2.6.25.
+@item
+When using @code{UTIME_OMIT} for the modification time, but specifying
+an access time, some systems fail to update the change time:
+Linux kernel 2.6.32.
@end itemize
Portability problems not fixed by Gnulib: