bug#22096: 25.0.50; reading from fifo breaks display

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sat, 5 Dec 2015 12:09:08 -0500
> From: Mark Oteiza <mvoteiza@udel.edu>
> Cc: 22096@debbugs.gnu.org
> 
> On 05/12/15 at 06:45pm, Eli Zaretskii wrote:
> > > From: Mark Oteiza <mvoteiza@udel.edu>
> > > Date: Sat, 05 Dec 2015 10:58:38 -0500
> > > 
> > > > Anyway, you are reading a binary byte stream from an audio daemon, so
> > > > I think you cannot expect it to be displayed in any human-readable
> > > > way, let alone hope that the major mode in effect in *scratch will be
> > > > able to fontify it in some reasonable way.  You should use
> > > > insert-file-contents-literally instead, I think.  (And I very much
> > > > doubt that "visiting" a non-regular file makes sense, but maybe I'm
> > > > missing something.)
> > > 
> > > Right, I didn't expect VISIT=t to make sense, but the resulting breakage
> > > is unexpected.
> > 
> > Emacs tries to decode the binary stream (unless you use the -literally
> > variant), and the result could look (to Emacs) like some text that
> > fits some font-locking or paren-matching pattern.
> 
> The same display oddity does still happen with
> 
> (insert-file-contents-literally "/tmp/mpd.fifo" t 0 10 nil)
> 
> and nothing appears to be inserted

What is the value returned by the function?