Segmentation fault on touch event

[msrd0]

After #50 was merged, I wanted to try out the new feature and compiled the git version on my laptop. However, as soon as I touch the touchscreen after I started slurp, I get a segmentation fault. Unfortunately I don't know how to produce a proper backtrace since I can't type bt while slurp is still in front of my entire screen. This is the best I've gotten by killing slurp from another tty after the segmentation fault:

(gdb) run
Starting program: /home/msrd0/git/slurp/build/slurp 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/usr/lib/libthread_db.so.1".

Program received signal SIGSEGV, Segmentation fault.
move_seat (seat=0x555555570440, surface_x=131094, surface_y=96053) at ../main.c:34
34              int x = wl_fixed_to_int(surface_x) + seat->current_output->logical_geometry.x;
(gdb) bt
#0  move_seat (seat=0x555555570440, surface_x=131094, surface_y=96053) at ../main.c:34
#1  0x0000555555559766 in touch_handle_motion (data=<error reading variable: Cannot access memory at address 0x7fffffffda58>, touch=<error reading variable: Cannot access memory at address 0x7fffffffda50>, 
    time=<error reading variable: Cannot access memory at address 0x7fffffffda4c>, id=<error reading variable: Cannot access memory at address 0x7fffffffda48>, x=<error reading variable: Cannot access memory at address 0x7fffffffda44>, 
    y=<error reading variable: Cannot access memory at address 0x7fffffffda40>) at ../main.c:308
Backtrace stopped: Cannot access memory at address 0x7fffffffda78
(gdb) q

If I can provide any other debugging help please let me know.

[emersion]

Can you provide WAYLAND_DEBUG=1 logs?

[emersion]

cc @gg-rewrite (just FYI)

[msrd0]

Can you provide WAYLAND_DEBUG=1 logs?

Sure:

$ WAYLAND_DEBUG=1 slurp
[1403252.557]  -> [email protected]_registry(new id wl_registry@2)
[1403252.594]  -> [email protected](new id wl_callback@3)
[1403252.756] [email protected]_id(3)
[1403252.774] [email protected](1, "wl_shm", 1)
[1403252.786]  -> [email protected](1, "wl_shm", 1, new id [unknown]@4)
[1403252.800] [email protected](2, "zwp_linux_dmabuf_v1", 3)
[1403252.816] [email protected](3, "wl_drm", 2)
[1403252.832] [email protected](4, "wl_compositor", 4)
[1403252.850]  -> [email protected](4, "wl_compositor", 4, new id [unknown]@5)
[1403252.877] [email protected](5, "wl_subcompositor", 1)
[1403252.892] [email protected](6, "wl_data_device_manager", 3)
[1403252.904] [email protected](7, "zwlr_gamma_control_manager_v1", 1)
[1403252.916] [email protected](8, "gtk_primary_selection_device_manager", 1)
[1403252.935] [email protected](9, "zxdg_output_manager_v1", 3)
[1403252.956]  -> [email protected](9, "zxdg_output_manager_v1", 1, new id [unknown]@6)
[1403252.994] [email protected](10, "org_kde_kwin_idle", 1)
[1403253.010] [email protected](11, "zwp_idle_inhibit_manager_v1", 1)
[1403253.025] [email protected](12, "zwlr_layer_shell_v1", 2)
[1403253.046]  -> [email protected](12, "zwlr_layer_shell_v1", 1, new id [unknown]@7)
[1403253.075] [email protected](13, "xdg_wm_base", 2)
[1403253.096] [email protected](14, "zwp_tablet_manager_v2", 1)
[1403253.117] [email protected](15, "org_kde_kwin_server_decoration_manager", 1)
[1403253.139] [email protected](16, "zxdg_decoration_manager_v1", 1)
[1403253.161] [email protected](17, "zwp_relative_pointer_manager_v1", 1)
[1403253.181] [email protected](18, "zwp_pointer_constraints_v1", 1)
[1403253.205] [email protected](19, "wp_presentation", 1)
[1403253.228] [email protected](20, "zwlr_output_manager_v1", 1)
[1403253.250] [email protected](21, "zwlr_export_dmabuf_manager_v1", 1)
[1403253.269] [email protected](22, "zwlr_screencopy_manager_v1", 2)
[1403253.292] [email protected](23, "zwlr_data_control_manager_v1", 2)
[1403253.314] [email protected](24, "zwp_primary_selection_device_manager_v1", 1)
[1403253.337] [email protected](25, "zwp_virtual_keyboard_manager_v1", 1)
[1403253.357] [email protected](26, "zwlr_virtual_pointer_manager_v1", 1)
[1403253.379] [email protected](27, "zwlr_input_inhibit_manager_v1", 1)
[1403253.400] [email protected](28, "wl_seat", 7)
[1403253.421]  -> [email protected](28, "wl_seat", 1, new id [unknown]@8)
[1403253.448] [email protected](29, "zwp_pointer_gestures_v1", 1)
[1403253.471] [email protected](30, "wl_output", 3)
[1403253.491]  -> [email protected](30, "wl_output", 3, new id [unknown]@9)
[1403253.520] [email protected](9876)
[1403253.533]  -> [email protected]_surface(new id wl_surface@3)
[1403253.547]  -> [email protected]_layer_surface(new id zwlr_layer_surface_v1@10, wl_surface@3, wl_output@9, 3, "selection")
[1403253.585]  -> [email protected]_xdg_output(new id zxdg_output_v1@11, wl_output@9)
[1403253.603]  -> [email protected]_anchor(15)
[1403253.614]  -> [email protected]_keyboard_interactivity(1)
[1403253.624]  -> [email protected]_exclusive_zone(-1)
[1403253.636]  -> [email protected]()
[1403253.666]  -> [email protected]_pool(new id wl_shm_pool@12, fd 5, 2304)
[1403253.861]  -> [email protected](6912)
[1403254.790]  -> [email protected](16128)
[1403254.822]  -> [email protected](34560)
[1403254.856]  -> [email protected](71424)
[1403254.917]  -> [email protected](145152)
[1403255.045]  -> [email protected](292608)
[1403256.149]  -> [email protected](587520)
[1403258.667]  -> [email protected](1177344)
[1403268.711]  -> [email protected](new id wl_callback@13)
[1403268.878] [email protected]_id(13)
[1403268.892] [email protected](7)
[1403268.897]  -> [email protected]_pointer(new id wl_pointer@14)
[1403268.904]  -> [email protected]_keyboard(new id wl_keyboard@15)
[1403268.909]  -> [email protected]_touch(new id wl_touch@16)
[1403268.915] [email protected](0, 0, 310, 170, 0, "Unknown", "0x0779", 0)
[1403268.938] [email protected](1, 1920, 1080, 60024)
[1403268.949] [email protected](1)
[1403268.954] [email protected]()
[1403268.958] [email protected]_position(0, 0)
[1403268.967] [email protected]_size(1920, 1080)
[1403268.979] [email protected]()
[1403268.984] [email protected]()
[1403268.988] [email protected](9877, 1920, 1080)
[1403269.001]  -> [email protected]_configure(9877)
[1403269.049]  -> [email protected]_pool(new id wl_shm_pool@17, fd 6, 8294400)
[1403269.072]  -> [email protected]_buffer(new id wl_buffer@18, 0, 1920, 1080, 7680, 0)
[1403269.102]  -> [email protected]()
[1403273.670]  -> [email protected](new id wl_callback@19)
[1403273.692]  -> [email protected](wl_buffer@18, 0, 0)
[1403273.700]  -> [email protected](0, 0, 1920, 1080)
[1403273.710]  -> [email protected]_buffer_scale(1)
[1403273.714]  -> [email protected]()
[1403273.718] [email protected](9877)
[1403273.724]  -> [email protected]_surface(new id wl_surface@13)
[1403277.449] [email protected]_id(17)
[1403277.470] [email protected](1, fd 5, 48373)
[1403278.967] [email protected]()
[1403278.983] [email protected](9879, wl_surface@3, 1569.257812, 712.921875)
[1403278.996]  -> [email protected]_buffer_scale(1)
[1403279.007]  -> [email protected]_buffer(new id wl_buffer@17, 347904, 24, 24, 96, 0)
[1403279.034]  -> [email protected](wl_buffer@17, 0, 0)
[1403279.053]  -> [email protected]_cursor(9879, wl_surface@13, 11, 11)
[1403279.079]  -> [email protected]()
[1403279.085] [email protected](9882, wl_surface@3, array)
[1403279.103] [email protected](9883, 0, 0, 0, 0)
[1403287.488] [email protected]_id(19)
[1403287.563] [email protected](767070418)
[1403362.603] [email protected](9884, 767070493, 28, 0)
[1404486.639] [email protected](9885, 767071617, wl_surface@3, 0, 546.269531, 353.359375)
[1404486.745] [email protected]()
[1404486.765] [email protected](9886, wl_surface@3)
[1404495.270] [email protected](767071626, 0, 552.074219, 356.574219)
Segmentation fault (core dumped)

[emersion]

Ah, this is fixed in Sway master.

[msrd0]

Ok I can confirm it works with sway-git package. Sorry for bothering you.

[emersion]

Let's keep this open, we shouldn't segfault even if the compositor sends this sequence of events.

[msrd0]

Yeah I agree, sorry for closing

[NilsIrl]

@msrd0 You can run gdb inside of tmux (maybe screen as well) to get a backtrace.

[msrd0]

Good idea, here is the full backtrace through tmux:

Reading symbols from ./build/slurp...
(gdb) run
Starting program: /home/msrd0/git/slurp/build/slurp 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/usr/lib/libthread_db.so.1".

Program received signal SIGSEGV, Segmentation fault.
move_seat (seat=0x555555570440, surface_x=30379, surface_y=58882) at ../main.c:34
34              int x = wl_fixed_to_int(surface_x) + seat->current_output->logical_geometry.x;
(gdb) bt full
#0  move_seat (seat=0x555555570440, surface_x=30379, surface_y=58882) at ../main.c:34
        x = 1431769344
        y = 0
#1  0x0000555555559766 in touch_handle_motion (data=0x555555570440, touch=0x555555571810, time=1020022958, id=0, x=30379, y=58882) at ../main.c:308
        seat = 0x555555570440
#2  0x00007ffff76f869a in ffi_call_unix64 () from /usr/lib/libffi.so.6
No symbol table info available.
#3  0x00007ffff76f7fb6 in ffi_call () from /usr/lib/libffi.so.6
No symbol table info available.
#4  0x00007ffff7e36e92 in ?? () from /usr/lib/libwayland-client.so.0
No symbol table info available.
#5  0x00007ffff7e336c1 in ?? () from /usr/lib/libwayland-client.so.0
No symbol table info available.
#6  0x00007ffff7e34ccc in wl_display_dispatch_queue_pending () from /usr/lib/libwayland-client.so.0
No symbol table info available.
#7  0x000055555555ac5d in main (argc=1, argv=0x7fffffffdf38) at ../main.c:844
        state = {running = true, edit_anchor = false, display = 0x555555569d00, registry = 0x55555556e880, shm = 0x555555570c30, compositor = 0x555555570d10, layer_shell = 0x555555570e40, xdg_output_manager = 0x555555570da0, outputs = {prev = 0x555555570590, 
            next = 0x555555570590}, seats = {prev = 0x555555570458, next = 0x555555570458}, xkb_context = 0x55555556dea0, colors = {background = 4294967104, border = 255, selection = 0}, border_weight = 2, display_dimensions = false, single_point = false, boxes = {
            prev = 0x7fffffffde08, next = 0x7fffffffde08}, result = {x = 0, y = 0, width = 0, height = 0, link = {prev = 0x0, next = 0x0}}}
        opt = -1
        format = 0x55555555c1c5 "%x,%y %wx%h"
        cursor_theme = 0x0
        cursor_size_str = 0x7fffffffe5ce "24"
        cursor_size = 24
        output = 0x7fffffffddb8
        seat = 0x7fffffffddc0
        output_tmp = 0x30
        seat_tmp = 0x20
        box = 0x401
        box_tmp = 0x7ffff7ca82d5 <_int_memalign+341>
(gdb) q

[gg-rewrite]

This was discussed in #50. While the current build will work with sway-git, the ideal behaviour should be handling touch and pointer events separately. I've created a PR #55 (whew, finally), please review it.

[msrd0]

Thanks @gg-rewrite, I just compiled your branch from #55 and it works as expected on sway stable on my ArchLinux laptop.