Re: Debugging M-x gdb

[Manuel Giraud via "Emacs development discussions." <emacs-devel@gnu.org>]

Eli Zaretskii <eliz@gnu.org> writes:

[...]

> Doesn't produce any output after attaching GDB to the Emacs process
> which consumes CPU?  That's not possible.  Please show all the
> commands you did, starting from invoking Emacs that will later consume
> CPU, including commands inside Emacs and outside it.
>
> Note that the GDB you attach to Emacs should be a new GDB process, not
> the one you ran inside Emacs.

Disclaimer: I'm using OpenBSD.  'egdb' is the somewhat recent
version (9.2) from packages (there is an old bundled gdb but it does not
support -i=mi).  In the mean time, I've found that this shows with other
executables I would try to debug from Emacs: I'm usin xclock here.
'~/bin/emacs-debug' is Emacs compiled with the following options:

         CFLAGS="-O0 -g3" ./configure \
	 --bindir=$HOME/bin --program-suffix=-debug \
 	 --enable-checking="yes,glyphs" \
	 --enable-check-lisp-object-type

Here is my recipe:

* From a xterm:
       egdb ~/bin/emacs-debug
       (gdb) source ~/emacs-repo/src/.gdbinit
       (gdb) set args -Q
       (gdb) run

* Into this Emacs:

       M-x gdb
       Run gdb (like this): egdb -i=mi /usr/X11R6/bin/xclock
       Enable querying debuginfod servers for this session? (y or n) n
       M-x gdb-many-windows

* Into this Emacs *gud-xclock* buffer:
       (gdb) run    # then from another terminal: pkill xclock
       [Inferior 1 (process 76899) exited with code 01]

Now Emacs starts spinning the CPU.

* Into the first xterm with GDB:

       (gdb) thread apply all bt

... nothing (even after quitting the Emacs *gud-xclock* buffer and
that the CPU goes back to normal).
-- 
Manuel Giraud