Arch Linux

Seems to affect only X11 sessions.

I also ran into this problem. I solved it by downgrading to yesterdays packages (Server=https://archive.archlinux.org/repos/2019/09/21/$repo/os/$arch)
It downgraded the following packages:
acpid (2.0.32-1 -> 2.0.31-1)
gcc8-libs (8.3.0-3 -> 8.3.0-2)
gcc8 (8.3.0-3 -> 8.3.0-2)
glm (0.9.9.6-2 -> 0.9.9.6-1)
mutter (3.34.0+30+gb5775e3d8-1 -> 3.34.0+6+gab7af2d0c-1)
gnome-shell (1:3.34.0+148+g506b75fc7-1 -> 1:3.34.0+94+g3d86e6e79-1)
openssh (8.0p1-3 -> 8.0p1-2)
python-xlib (0.25-1 -> 0.24-1)
python2-xlib (0.25-1 -> 0.24-1)

This happens on Wayland/XWayland too. Getting random gnome-shell crashes when launching Firefox (in X11 mode):
gnome-shell[10978]: segfault at 0 ip 00007fbb6f6ebaa0 sp 00007fff51440d48 error 4 in libcairo.so.2.11703.0[7fbb6f6c5000+cf000]
Code: 74 10 8b 00 85 c0 75 0a 8b 87 70 01 00 00 c3 0f 1f 00 48 83 ec 08 bf 0d 00 00 00 e8 4a fe fe ff 31 c0 48 83 c4 08 c3 0f 1f 00 <48> 8b 07 48 85 c0 74 10 8b 00 85 c0 75 0a 8b 87 74 01 00 00 c3 0f

I was experiencing related shell crashes, particularly regarding fullscreen and geometry. The gnome-shell and mutter packages pull a lot of 3.36 alpha code from git that isn't ready. See  FS#63890 . There's no 3-34 branch for just 3.34 bug fixes yet and seems @heftig just got a little trigger-happy.

I'm experiencing same shell crashes as well, in my case when I try to connect to a remote host with Remmina. Downgrading gnome-shell from 1:3.34.0+148+g506b75fc7-1 to 1:3.34.0+94+g3d86e6e79-1) seems to fix that.

Probably https://gitlab.gnome.org/GNOME/gnome-shell/issues/1678

That issue claims that commit https://gitlab.gnome.org/GNOME/gnome-shell/commit/506b75fc7f3a1beeee6141ccb8edb6731c45cc6a caused the segfaults -- that commit is not in a stable branch or in a tagged release, only in master.

Look again what the ArchLinux package rolls out as the time of writing: https://git.archlinux.org/svntogit/packages.git/commit/trunk?h=packages/gnome-shell&id=217c32df062c2d40d1ae4e736be18bce92a7b6de

Yes. Exactly 506b75fc7f3a1beeee6141ccb8edb6731c45cc6a

I am also experiencing reproduceable crashes with some applications (Remmina upon opening a remote session, Gitkraken, PyCharm).

Jan said in my bug that master is intended for 3.34.1, so I'll assume he knows what he's doing. The fix for the issue MHami mentions hasn't been merged yet, and I believe that's the crasher involved, so roll back or build your own until then.

Today's update
> [2019-09-24 20:21] [ALPM] upgraded gnome-shell (1:3.34.0+148+g506b75fc7-1 -> 1:3.34.0+152+g0fdbde910-1)
seems to have fixed it for me. At least I can open FF again without gnome-shell crashing. Maybe someone else affected could confirm?

I can confirm that 1:3.34.0+152+g0fdbde910-1 fixed the issue for me (about 50% chance of crashing when launching a JetBrains IDE)