bug#22356: 25.0.50; emacs-25 very crashy with ivy-mode

[Eli Zaretskii <eliz@gnu.org>]

> Cc: 22356@debbugs.gnu.org
> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Tue, 12 Jan 2016 19:48:42 +0300
> 
> > I doubt that.  Maybe that ivy-mode update exposed some old bug?  Did
> > you try to go back the old version of ivy-mode?
> 
> Alas, no. I went back from the version in MELPA to swiper 0.7.0 (it 
> includes ivy-mode) which was published to GNU ELPA a month ago.

Was anything else on your system updated lately?  Some library,
perhaps, or some system component?  The problems look quite basic, for
example this:

> Starting program: /home/gutov/vc/emacs/src/emacs
> [Thread debugging using libthread_db enabled]
> Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
> [New Thread 0x7fffe6848700 (LWP 9356)]
> [New Thread 0x7fffe5a21700 (LWP 9357)]
> [New Thread 0x7fffe5220700 (LWP 9358)]
> *** Error in `/home/gutov/vc/emacs/src/emacs': free(): invalid pointer: 
> 0x00000000029d5c40 ***
> 
> Program received signal SIGABRT, Aborted.
> 0x00007ffff14a5267 in __GI_raise (sig=sig@entry=6) at 
> ../sysdeps/unix/sysv/linux/raise.c:55
> 55	../sysdeps/unix/sysv/linux/raise.c: No such file or directory.

means that glibc detected an invalid pointer being passed to 'free'.
It's glibc which raises SIGABRT here, AFAIU, and it does that because
if that invalid 'free' call.

> Sometimes, I'm also getting a graphical glitch in the minibuffer: one or 
> few "character not found" glyphs flickering against the right window 
> border right before the crash.

When heap memory is corrupted, anything can happen.