bug#34969: 26.2; `emacs -Q` unable to copy \200's eight-bit detail buffer

[Eli Zaretskii <eliz@gnu.org>]

> From: Van L <van@scratch.space>
> Date: Mon, 25 Mar 2019 14:14:47 +1100
> Cc: 34969@debbugs.gnu.org
> 
> >> : 7 `emacs -Q`
> >> : [this is the first time for `emacs -Q]
> >> : [has problem the forth time run for thise version]
> >> : [on XQuartz]
> >> : [~/bin/emacs26.2r1 links to \200nfs\200/build/emacs26.2-rc1/bin/emacs-26.2]
> >> : GNU Emacs 26.2 (build 1, x86_64-apple-darwin15.6.0, X toolkit)
> >> : of 2019-03-21
> > 
> > Does "the forth time" mean do all the steps 4 times before the problem
> > happens?  Or does it mean repeat only some of the steps 4 times?
> 
> 4th time means the forth time starting from the initial condition before Emacs is started for the same Emacs version to run in isolation without other instances running.

So you actually started Emacs 4 times, and only on the 4th restart it
exhibited the problem?  If so, I'm quite sure this is caused by some
external software, perhaps something that takes ownership of the
clipboard contents, e.g. because it wants to let you have several
different clipboard buffers.  Do you have something like that
installed and active?

> > IOW, can you please show the transcript of repeated steps in these
> > situations?
> 
> That is under the section `-- A` in the bug-report. 
> I had hoped the trace was caught in the bug-report.

Section A just gives a single sequence, but it doesn't tell how to do
that several times, i.e. what exactly is repeated N times.

> > What happens if you set interprogram-cut-function and
> > interprogram-paste-function to nil?
> 
> Will do the next time I get a chance.

If I'm right, the problem will disappear.

> > (And why do your symlink targets include \200 characters?)
> 
> I used `C-x 8 RET horizontal ellipsis` the email program was unable to process.
> The \200 was what the email program used as substitute.

Strange email program: \200 is an unassigned codepoint.