bug#23743: 24.5; Opening output file: invalid argument, .../foo-<-4-n.el

[Eli Zaretskii]

> Date: Fri, 10 Jun 2016 10:35:54 -0700 (PDT)
> From: Drew Adams <drew.adams@oracle.com>
> 
> emacs -Q
> 
> C-x C-f foo-<-4-n.el
> 
> Type some text in that file buffer.
> 
> C-x C-s  ; try to save it.
> 
> Saving file d:/usr/drew/drews-lisp-20/foo-<-4-n.el...
> basic-save-buffer-2: Opening output file: invalid argument, 
> d:/.../foo-<-4-n.el
> 
> Apparently it doesn't like `<' in a file name?

Yes, Windows doesn't allow that.

> If so, and if that is "normal", then the user should get a much
> better error message than this.

That's the error that comes from the filesystem, Emacs doesn't know
any better.