Sorry, I don't have a linux machine to test now. I tested that this bug
still exists on Emacs 24.3.1, running on 3.10.0-693.5.2.el7.x86_64
of Scientific Linux 7.3 by running a remote X-window. The * mark updates
when I am under user home folder but not updating when I am in a file in
/tmp. I don't have access to a more recent version of Emacs and was unable
to install a more recent version of emacs there. If the bug is no longer
there, it may be just fine now.

Lars Ingebrigtsen <larsi@gnus.org> 于2021年7月16日周五 上午1:17写道：

> Yi Wang <tririverwangyi@gmail.com> writes:
>
> > If I set frame-title as:
> >
> > (setq frame-title-format "%b  %* ")
> >
> > The modified mark * will display correctly for normal files. But for
> > files in /tmp (where tmpfs is enabled), the modified mark almost never
> > appears (though actually buffer is modified).
>
> (I'm going through old bug reports that unfortunately got little response
> at
> the time.)
>
> I tried reproducing this on Debian/bullseye with Emacs 28 now in this
> directory:
>
> tmpfs           1.6G  896K  1.6G   1% /run/user/1000
>
> And I was unable to -- the "*" appeared in the frame title as expected.
>
> Are you still seeing this issue in recent Emacs versions?
>
> --
> (domestic pets only, the antidote for overdose, milk.)
>    bloggy blog: http://lars.ingebrigtsen.no
>