Hello Eli,

Thank you. I had to set first the breakpoint, as GDB prompt would not come back if I run emacs.

OK, here it is attached.

On Thu, Jul 27, 2017 at 08:18:00PM +0300, Eli Zaretskii wrote:
> > Date: Thu, 27 Jul 2017 10:38:27 +0300
> > From: Jean Louis <bugs@gnu.support>
> > Cc: 27816@debbugs.gnu.org
> > 
> > I am starting Emacs through screen, without X windows. So I started as:
> > 
> > gdb screen
> > 
> > then I do:
> > 
> > breakpoint x_error_quitter
> > 
> > It asks me for future loaded libraries, I said y.
> > 
> > Then I "run" and get screen and bash.
> > 
> > Then I start emacs as 
> > 
> > emacs --user admin --chdir /home/data1/protected (that is my home dir)
> 
> No, I think this is a mistake.  You should first start screen, then
> start GDB from that like this:
> 
>   gdb emacs
> 
> Then when GDB shows its prompt, type
> 
>   (gdb) break x_error_quitter
>   (gdb) run  --user admin --chdir /home/data1/protected
> 
> (The "(gdb)" part is the GDB prompt, you don't need to type it.)
> And then continue as you usually would:
> 
> > And then I connect to emacs as emacsclient
> > 
> > and evaluate (x-synchronize t)
> > 
> > and then if I connect each 4th or 5th time, not clearly known why,
> > then I get that bug, and X frame of new emacsclient is not appearing.
> > 
> > But back in debugger I do not see much, emacs as server is still
> > running.
> 
> If you start Emacs as above, you should see GDB take control when the
> problem happens.  Then type
> 
>   (gdb) thread apply all bt
> 
> and post here everything it displays.