Here are some more tests:

1. It doesn't get stuck when debugging a "hello-world.c" program. Thus it
depends on the executable.
2. Regarding toggle-debug-on-quit and C-g, it doesn't work. No backtrace is
produced and the CPU continues to be at 100%.
3. I tried running edebug on gdb, which wasn't easy. I had to manually
first do eval-buffer on gdb-mi.el and gud.el. But in the end I managed and
found that the CPU is spend during (run-hooks 'gdb-mode-hook) . I'll try to
investigate it further in the next few days.

Regards,
Dov

On Wed, Jan 25, 2012 at 02:37, Glenn Morris <rgm@gnu.org> wrote:

>
> >> I tried again with emacs -Q and the same thing happens. To be more
> >> precise the startup time is about 40s at 100% CPU.
>
> Is this with everything you try to debug, or just certain things?
>
> Can you try M-x toggle-debug-on-quit, then interrupt Emacs with ctrl-g
> during those 40 seconds and see if you get a backtrace?
>
> Or try M-x edebug-defun on the `gdb' function, step through it, and see
> what is taking the time.
>
> Guesses: do you have a huge .gdb_history or ~/.gdbinit file?
>