In the latest update saga, gnome-software has started segfaulting. Of course my parents don't notice this. It just means they won't get notifications for security updates, and the PC will get horrible and insecure. The first page of Google shows nothing, to explain why this Debian Desktop is failing to deliver security update notifications (again, sigh).
Have the following symptoms been seen by others? Can we provide an explanation? Does it admit a permanent fix?
(Short of the root cause: inadequate resources for Debian Desktop, compared to other desktops).
sudo journalctl suggests this is a NULL pointer dereference in libgs_plugin_systemd-updates.so. (The last three digits of the Instruction Pointer are the same in each case).
Nov 22 14:59:39 drystone kernel: pool: segfault at 0 ip 00007f86c4d6f6d6 sp 00007f86b92249d0 error 4 in libgs_plugin_systemd-updates.so[7f86c4d6e000+2000]
The journal shows it crashed 66 times before today, starting from 2017-10-18. The current version of gnome-software was upgraded to on 2017-09-23. This would have been when I upgraded the machine from Debian Wheezy to Stretch. I know I was able to open gnome-software immediately after the upgrade.
Today it was crashing whenever I started it, until I took the steps to install gnome-software-dbgsym. Removing the -dbgsym package didn't get it to start crashing again. It must have been something about the state of apt. For the future, I've enabled capturing backtraces by installing
The closest I can find is a matching gnome-software segfault which happened to be logged in a report against a completely different program. This turned up in the results for "libgs_plugin_systemd-updates segfault". (I'm guessing the Kali version in question included the same binary from Debian Stretch). Searching more specifically for this segfault message, Google's index currently only includes the Kali report and my question here.
$ apt-cache policy gnome-software gnome-software: Installed: 3.22.5-1 Candidate: 3.22.5-1 Version table: *** 3.22.5-1 500 500 http://ftp.uk.debian.org/debian stretch/main amd64 Packages 100 /var/lib/dpkg/status
apt-get upgrade showed no pending updates for gnome-software (or packagekit).
$ gnome-software 14:59:38:0408 Gs failed to call gs_plugin_add_updates_historical on packagekit-offline: The package id's 'curl;7.52.1-5+deb9u2;amd64;debian-stable-main&
[snip. this warning happens anyway when it doesn't crash]
&xwayland;2:1.19.2-1+deb9u2;amd64;debian-stable-main' are not valid Segmentation fault
 The Debian Desktop does not come with any popup for crashes.
My parents are used to it as a multi-user system and it's possible they log out to gdm before shutting down, which wouldn't show the nice tickybox to reboot and install updates. Apparently my parents tend to shut down directly without logging out first. So that's good, at least they should still see "reboot and install updates" when they shut down. (It appears as a tickbox which is ticked by default).