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

[Dima Kogan]

Andreas Schwab <schwab@linux-m68k.org> writes:

> Dima Kogan <dima@secretsauce.net> writes:
>
>> Emacs from git says
>>
>>     (gdb) show height
>>     Number of lines gdb thinks are in a page is 24.
>
> This is something that needs to be fixed in gdb, see init_page_info in
> gdb/utils.c.

Hi. Thanks for replying. Looking at gdb/utils.c, apparently gdb looks at
the EMACS environment variable, which was set previously but is not
anymore:

  
https://github.com/emacs-mirror/emacs/commit/beaab898968caf8b243a33d24824d430fabc31fc

This patch in emacs is what broke it. Options:

1. revert above patch
2. patch gdb to look at INSIDE_EMACS not EMACS
3. handle this inside emacs, not relying on gdb behavior

I like 3. Emacs should be responsible for things emacs wants, not
external applications, even if they're GNU applications.

Also, it looks like gdb checks EMACS in a few more places, and I haven't
looked at those yet.

Thoughts?