Re: Random segfaults when using M-x.

[Eli Zaretskii <eliz@gnu.org>]

> Date: Fri, 5 Jun 2015 10:20:49 +0000
> From: Zack Piper <zack@apertron.net>
> 
> I get the following backtrace (seemingly at random) when pressing M-x,
> this happens sometimes 2 times a day, I didn't report a bug because I
> couldn't reproduce it reliably, but it randomly happened 2 times just
> now when trying to debug what was happening (both times during trying
> to use M-x). Shall I try disecting my Emacs configuration
> (https://github.com/zackp30/dotfiles) or wait to see if that's not
> needed and it's a known bug?

This is a strange backtrace: how come XUNTAG called recursive_edit_1?
I'm guessing this is because your binary is optimized, and so the
backtrace is not really reliable.

Can you rebuild Emacs without optimizations, preferably configured
with --enable-checking=yes, and run Emacs under GDB, so that we could
both catch the error before the crash and get a better backtrace?

Also, please report all this via "M-x report-emacs-bug RET", so that
it's recorded in the bug tracker.

Anyway, this cannot be due to your configuration, because the reason
for the crash is most probably an invalid NULL face, which should
never happen.

Thanks.