[Bug]: GLib-GIO-CRITICAL after sending SIGINT

[pabloab]

Checklist

• I agree to follow the Code of Conduct that this project adheres to.
• I have searched the issue tracker for a bug that matches the one I want to file, without success.
• If this is an issue with a particular app, I have tried filing it in the appropriate issue tracker for the app (e.g. under https://github.com/flathub/) and determined that it is an issue with Flatpak itself.
• This issue is not a report of a security vulnerability (see here if you need to report a security issue).

Flatpak version

1.11.1

What Linux distribution are you using?

Ubuntu

Linux distribution version

20.04

What architecture are you using?

x86_64

How to reproduce

1. Install mpv: flatpak install flathub io.mpv.Mpv
2. Run flatpak run io.mpv.Mpv anyvideo.webm (same with avi and any format I tried).
3. Press Ctrl+C (SIGINT).

Expected Behavior

Just to stop.

Actual Behavior

Stops and this is sent to stderr:

(process:2): GLib-GIO-CRITICAL **: 18:25:10.679: g_dbus_connection_emit_signal: assertion 'G_IS_DBUS_CONNECTION (connection)' failed
(process:2): GLib-GIO-CRITICAL **: 18:25:10.685: g_dbus_connection_unregister_object: assertion 'G_IS_DBUS_CONNECTION (connection)' failed
(process:2): GLib-GIO-CRITICAL **: 18:25:10.685: g_dbus_connection_unregister_object: assertion 'G_IS_DBUS_CONNECTION (connection)' failed

Additional Information

Following this mpv issue and this mpv flatpak package issue. They believe the issue should be addressed here.

Of course, I could hide this (and all stderr) with 2> /dev/null but maybe flatpak developers are interested in handling SIGINT and close everything gracefully. Even removing the session bus (using Flatseal) doesn't stop the error message from showing up.

[smcv]

This isn't a Flatpak bug. The process ID in the messages is 2, indicating that they're being emitted by a process inside the container created by Flatpak, which is almost certainly mpv (of course, the bug could be in any library or loadable module loaded by mpv, not necessarily mpv itself).

[smcv]

If you run mpv as

G_DEBUG=fatal-criticals flatpak run io.mpv.Mpv /path/to/some/video

it will crash after emitting the first critical warning. The crash dump collected by systemd-coredump indicates that, yes, this is the /app/bin/mpv process inside the container, and the bug is probably in its /app/etc/mpv/scripts/mpris.so plugin.