bug#21777: 25.0.50; gud-gdb uses a pager, which is harmful inside emacs

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: dima@secretsauce.net,  21777@debbugs.gnu.org,  schwab@linux-m68k.org
> Date: Mon, 21 Sep 2020 16:07:06 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> I worked up a patch for this, but in testing, there's a number of
> >> problems.
> >
> > Do you see the original problem with a recent version of GDB?  In the
> > discussion, I mentioned that the change to follow that of Emacs was
> > installed in GDB back then, so it's reasonable to expect that we no
> > longer have a problem described in this bug report.
> 
> No, the problem is still there -- If you say `M-x gud-gdb' and then
> issue a backtrace, then the gdb pager kicks in.

This is very strange.  I clearly see in GDB the code to set unlimited
page height.  Any GDB version later than 7.10 should have this.

If you invoke "M-x gud-gdb", then type "show height" at the "(gdb)"
prompt in the interaction buffer, what do you see?

And if you then type "show environment INSIDE_EMACS" at the "(gdb)"
prompt, what do you see?