bug#17386: 24.3.90; emacs_abort in cmcheckmagic

[Eli Zaretskii]

> From: Andreas Schwab <schwab@linux-m68k.org>
> Cc: theonewiththeevillook@yahoo.fr,  17386@debbugs.gnu.org
> Date: Sat, 03 May 2014 10:56:00 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Can we be sure that tmux reserves its line via that ioctl?
> 
> What do you mean with "reserves its line"?

What Nicolas reported (I know nothing about tmux, so cannot say this
better, sorry):

> tmux shows some sort of status line, which means that the client
> (emacs-in-gdb in my case) sees one line less.

and

> I tried splitting tmux (because of the related bug bug#16674) :
> (gdb) p FrameRows(current_tty)
> $4 = 20
> 
> (that's in the lower pane ; in the one above the answer is 21)

My understanding from this was that tmux reserves one screen line for
its status, and also that it can split a TTY into several portions,
each one emulating a separate terminal.