Getting a segmentation fault

[ukch]

I've just compiled dmenu-wl on my Debian Bullseye system, following the instructions. I can run the binary (e.g. with --help) but as soon as it receives input, I get a segfault. An example:

$ echo "hi" | dmenu # this works fine
...
$ echo "hi" | ./build/dmenu-wl
wl_registry@2: error 0: invalid version for global wl_output (26): have 2, wanted 3
mmap failed: Invalid argument
[1]    90785 done                echo "hi" | 
       90786 segmentation fault  ./build/dmenu-wl

Please let me know if I can provide any further debugging info.

[nyyManni]

Could you tell me which compositor (and which version) are you using. wayland is telling you that your compositor is only providing version 2 of the wl_output protocol, but the application is requesting version 3, and thus returns a null which then causes the segfault.

I will also double-check what functionality we need from version 3 (if any) The version 3 was a copy-paste requirement from swaybar, so it might happen that we can downgrade the version requirement to 2.

[nyyManni]

Turns out that the version bump from 2 to 3 happened at 2016, so your compositor is working with a quite old protocol.

However, the change between 2 and 3 was not meaningful for dmenu-wl so I downgraded the requirement. It might be that there will be other issues to come, if other protocols are as out of date as wl_output was.

[ukch]

@nyyManni Thanks! I don't really understand Wayland, but I'm surprised to hear my compositor is quite old, as I'm on a fresh Debian testing install. I will have another check today and let you know if it works OK now...

[apiraino]

I'm surprised to hear my compositor is quite old

@ukch Slightly related, I use the Debian files to build my own Ubuntu packages for everything Sway related (from wl-roots, sway down to the latest utility like waybar and dmenu_wayland).

https://salsa.debian.org/swaywm-team/

Might be interesting for you, too :)

[ukch]

@nyyManni Unfortunately, it is still segfaulting. Git hash 68e08e8b, build dir removed and rebuilt.

[nyyManni]

Does it give the exact same error about the version, or something else?

[ukch]

@nyyManni No, this time it doesn't give any output, just "segmentation fault".

[nyyManni]

Okay, so we are hitting the "other issues to come" now.

So are you using sway or something else? If yes, what version (and what wlroots version) do you have?

[ukch]

Here's the result of running the above, with WAYLAND_DEBUG=1:

[759779.387]  -> wl_display@1.get_registry(new id wl_registry@2)
[759779.409]  -> wl_display@1.sync(new id wl_callback@3)
[759780.015] wl_display@1.delete_id(3)
[759780.030] wl_registry@2.global(1, "wl_drm", 2)
[759780.039] wl_registry@2.global(2, "wl_compositor", 4)
[759780.047]  -> wl_registry@2.bind(2, "wl_compositor", 4, new id [unknown]@4)
[759780.064] wl_registry@2.global(3, "wl_shm", 1)
[759780.072]  -> wl_registry@2.bind(3, "wl_shm", 1, new id [unknown]@5)
[759780.085] wl_registry@2.global(4, "wl_output", 2)
[759780.095]  -> wl_registry@2.bind(4, "wl_output", 2, new id [unknown]@6)
[759780.109] wl_registry@2.global(5, "zxdg_output_manager_v1", 3)
[759780.116]  -> wl_registry@2.bind(5, "zxdg_output_manager_v1", 2, new id [unknown]@7)
[759780.132] wl_registry@2.global(6, "wl_data_device_manager", 3)
[759780.140] wl_registry@2.global(7, "gtk_primary_selection_device_manager", 1)
[759780.152] wl_registry@2.global(8, "wl_subcompositor", 1)
[759780.164] wl_registry@2.global(9, "xdg_wm_base", 2)
[759780.177] wl_registry@2.global(10, "zxdg_shell_v6", 1)
[759780.192] wl_registry@2.global(11, "wl_shell", 1)
[759780.208] wl_registry@2.global(12, "gtk_shell1", 3)
[759780.222] wl_registry@2.global(13, "wp_viewporter", 1)
[759780.237] wl_registry@2.global(14, "zwp_pointer_gestures_v1", 1)
[759780.252] wl_registry@2.global(15, "zwp_tablet_manager_v2", 1)
[759780.268] wl_registry@2.global(16, "wl_seat", 5)
[759780.282]  -> wl_registry@2.bind(16, "wl_seat", 1, new id [unknown]@8)
[759780.297] wl_registry@2.global(17, "zwp_relative_pointer_manager_v1", 1)
[759780.309] wl_registry@2.global(18, "zwp_pointer_constraints_v1", 1)
[759780.320] wl_registry@2.global(19, "zxdg_exporter_v1", 1)
[759780.332] wl_registry@2.global(20, "zxdg_importer_v1", 1)
[759780.343] wl_registry@2.global(21, "zwp_linux_dmabuf_v1", 3)
[759780.352] wl_registry@2.global(22, "zwp_keyboard_shortcuts_inhibit_manager_v1", 1)
[759780.363] wl_registry@2.global(23, "zwp_text_input_manager_v3", 1)
[759780.375] wl_registry@2.global(24, "gtk_text_input_manager", 1)
[759780.386] wl_callback@3.done(15694)
[759780.393]  -> wl_display@1.sync(new id wl_callback@3)
[759780.483] wl_display@1.delete_id(3)
[759780.493] wl_output@6.geometry(0, 0, 340, 190, 0, "SHP", "0x149a", 0)
[759780.508] wl_output@6.mode(3, 1920, 1080, 59999)
[759780.517] wl_output@6.scale(1)
[759780.520] wl_output@6.done()
[759780.523] wl_seat@8.capabilities(3)
[759780.530]  -> wl_seat@8.get_keyboard(new id wl_keyboard@9)
[759780.538] wl_callback@3.done(15694)
[759780.544]  -> wl_compositor@4.create_surface(new id wl_surface@3)
mmap failed: Invalid argument

I'm not a wayland dev, and I don't really know anything about sway or wlroots. But I checked with my package manager and it looks like neither are installed. Shall I try installing sway and see if that fixes things @nyyManni?

[nyyManni]

If you don't have sway/wlroots installed, you are using some other de/wm, which most likely is nolt wlroots-based.

Are you using gnome or kde, perhaps?

[ukch]

Yes, sorry if I didn't already mention this, but I'm using Gnome.

[nyyManni]

That explains.

I don't officially support Gnome as it is not based on wlroots. However, I do have Gnome installed as a secondary desktop, so I can try if there is an easy way around that error. But if I hit a roadblock I am afraid there is not much to do.

Closing this.

[ukch]

Thanks. That explains a few things, and I hope you are able to get something working!