panic: interface conversion: interface {} is string, not uint32

[matperc]

panic: interface conversion: interface {} is string, not uint32

goroutine 1 [running]:
main.(*Command).waitForSignals(0xc0000c0120, 0xc00007c180)
        /home/runner/work/host-spawn/host-spawn/command.go:137 +0x1b5
main.(*Command).SpawnAndWait(0xc0000c0120)
        /home/runner/work/host-spawn/host-spawn/command.go:109 +0x997
main.main()
        /home/runner/work/host-spawn/host-spawn/main.go:121 +0x4fe

I use host-spawn to run commands from flatpak Emacs. Sometimes it crashes with this error. What could it be?

[1player]

No idea. Can you reproduce from a shell and provide the elisp incantations you're using to run host-spawn?

[matperc]

It's a complicated setup, I'll try to simplify a bit in the next days and see what happens.

Do I understand correctly that, even if the panic was handled, the command is still closing with HostCommandExited signal?

[matperc]

Ok I simplified my tries until this:

1. Download host-spawn-x86-64 v1.6.0
2. Download emacs from Flathub
3. Run emacs
4. M-x term inside emacs (Alt-x term RET)
5. Run host-spawn without arguments
6. Call some process for example top, or just wait
7. Some time later the error above appears, and the shell returns to flatpak

[1player]

I cannot reproduce. From Flathub's Emacs (started with a bare config), within a term, host-spawn is able to spawn an host shell, top works correctly for me, etc.

Can you provide any details about your linux distro? Can you reproduce the problem from inside a toolbox or distrobox container?

Your error seems to be caused by the fact that host-spawn, subscribed only to HostCommandExited DBus messages, receives an unexpected message and doesn't handle this case very well; it certainly should print a more helpful message than just panicking. I have seen weird errors from people using niche distros with missing or misconfigured flatpak/dbus.

If you are able to use git and compile go software, I can push some changes for you to test with.

[1player]

Please try the robustness branch, which should print a more helpful error when host-spawn crashes.

https://github.com/1player/host-spawn/tree/robustness

[matperc]

Thanks for taking your time to look into it.

I failed to mention that the issue appears after a lot of time, randomly between 10 minutes to some hour. It seems worse when the PC is used intensively.

What do you mean inside a distrobox? Instead of flatpak?

I never tried compile a Go program, but I will try later today.

I replicated the issue both on Fedora Silverblue and Fedora Workstation. Both updated to the lastest version

[matperc]

unexpected DBus message &dbus.Signal{Sender:"org.freedesktop.DBus", Path:"/org/freedesktop/DBus", Name:"org.freedesktop.DBus.NameOwnerChanged", Body:[]interface {}{"org.freedesktop.portal.Flatpak", "", ":1.123"}, Sequence:0x5}

Here we go

Here the error after the above ~ 20 minutes later

unexpected DBus message &dbus.Signal{Sender:"org.freedesktop.DBus", Path:"/org/freedesktop/DBus", Name:"org.freedesktop.DBus.NameOwnerChanged", Body:[]interface {}{"org.freedesktop.portal.Flatpak", ":1.123", ""}, Sequence:0x5}

It is very similar but it seems that the parameter of Body are swapped, I don't know what that means. At the same time I had a distrobox open similarly (distrobox->host-spawn->top) but without emacs and there was no problem.

Update:
This issue is reproducible even in other flatpaks. I run flatpak run --command=/bin/bash org.gnome.Calculator and then run host-spawn inside it. At the same time the issue closed both this instance and the Emacs one, with the same error:

unexpected DBus message &dbus.Signal{Sender:"org.freedesktop.DBus", Path:"/org/freedesktop/DBus", Name:"org.freedesktop.DBus.NameOwnerChanged", Body:[]interface {}{"org.freedesktop.portal.Flatpak", ":1.149", ""}, Sequence:0x5}

[1player]

Not sure what this message means, but I reckon host-spawn should check if it got the expected message, and ignored everything else. I'll work on a fix, thanks

On Tue, 12 Nov 2024, at 18:29, matperc wrote: `unexpected DBus message &dbus.Signal{Sender:"org.freedesktop.DBus", Path:"/org/freedesktop/DBus", Name:"org.freedesktop.DBus.NameOwnerChanged", Body:[]interface {}{"org.freedesktop.portal.Flatpak", "", ":1.123"}, Sequence:0x5}

`

…

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[1player]

Can you please try again with the latest commit on the robustness branch? Now we actually check the message name, and ignore anything that we don't care about.

[matperc]

Thanks for the fix, I have been working the whole day with no problem. I also applied a similar patch yesterday and the issue never occurred.

I am not sure if HostCommandExited is captured correctly, I am unable to verify it. Otherwise, for my use case, it works perfectly.

[1player]

Yes the fix is pretty straightforward, so I guess it won't crash again. I'll be merging into master and cutting a new release soon.

[1player]

Fix released with version 1.6.1 (sorry for the delay)