bug#17386: 24.3.90; emacs_abort in cmcheckmagic

[Eli Zaretskii]

> From: Nicolas Richard <theonewiththeevillook@yahoo.fr>
> Date: Wed, 28 May 2014 10:35:39 +0200
> Cc: 17386@debbugs.gnu.org
> 
> It happened again (at least it looks very very similar to me) but I'm
> afraid I'm not bringing much new information.
> 
> Anyway, just to show that it is the same problem :
> 
> (gdb) f 2
> #2  0x0812f9b7 in cmcheckmagic (tty=0x897de50) at cm.c:120
> 120             emacs_abort ();
> (gdb) l
> 115     cmcheckmagic (struct tty_display_info *tty)
> 116     {
> 117       if (curX (tty) == FrameCols (tty))
> 118         {
> 119           if (!MagicWrap (tty) || curY (tty) >= FrameRows (tty) - 1)
> 120             emacs_abort ();
> 121           if (tty->termscript)
> 122             putc ('\r', tty->termscript);
> 123           putc ('\r', tty->output);
> 124           if (tty->termscript)
> (gdb) p curY(tty)
> $1 = 41
> (gdb) p FrameRows(tty)
> $2 = 23
> 
> The situation was as follows: I had a detached tmux session with an
> "emacs -nw" in it (in gdb), and I had a graphical frame open also (via
> emacsclient). I then tried to reattach to the tmux session, and that's
> when emacs crashed.
> 
> I guess it would help to know what happens when tmux is detached.
> Perhaps emacs should receive some kind of notification, and that doesn't
> happen in some cases ? Next time I have to close emacs I'll try using
> screen instead of tmux.

What does it mean "detached tmux"?  How do you "attach" to a tmux
session, and what does that tell Emacs about the TTY that is being
attached?