segmentation violation running the hello example

[pekim]

cd examples/hello
CGO_ENABLED=0 go run .

interface 'xdg_toplevel' has no event 3
SIGSEGV: segmentation violation
PC=0x7f8a79613be5 m=3 sigcode=1 addr=0x18
signal arrived during cgo execution

goroutine 8 gp=0x3b676758c5a0 m=3 mp=0x3b67674cd008 [syscall, locked to thread]:
runtime.cgocall(0x5844c0, 0x3b67677b1040)
	/home/mike/.local/go/src/runtime/cgocall.go:167 +0x4b fp=0x3b676747d440 sp=0x3b676747d408 pc=0x4802ab
github.com/go-webgpu/goffi/internal/syscall.CallNFloat(0x7f8a7857d470, {0x7f8a6c0bd230, 0x7f8a6c0976b0, 0x3b67677bc000, 0x0, 0x0, 0x0}, {0x0, 0x0, 0x0, ...}, ...)
	/home/mike/go/pkg/mod/github.com/go-webgpu/goffi@v0.4.2/internal/syscall/syscall_unix_amd64.go:78 +0x20b fp=0x3b676747d538 sp=0x3b676747d440 pc=0x58446b
github.com/go-webgpu/goffi/internal/arch/amd64.(*Implementation).Execute(0xb180c0, 0xae98a0, 0x3b676747d898?, 0x421d85?, {0x3b676779a078, 0x3, 0x3})
	/home/mike/go/pkg/mod/github.com/go-webgpu/goffi@v0.4.2/internal/arch/amd64/call_unix.go:129 +0x785 fp=0x3b676747d860 sp=0x3b676747d538 pc=0x584d45
github.com/go-webgpu/goffi/ffi.executeFunction(...)
	/home/mike/go/pkg/mod/github.com/go-webgpu/goffi@v0.4.2/ffi/call.go:20
github.com/go-webgpu/goffi/ffi.CallFunctionContext({0x819d38?, 0xb180c0?}, 0xae98a0, 0x7f8a7857d470, 0x3b67677868a0, {0x3b676779a078, 0x3, 0x3})
	/home/mike/go/pkg/mod/github.com/go-webgpu/goffi@v0.4.2/ffi/ffi.go:229 +0xa7 fp=0x3b676747d8a8 sp=0x3b676747d860 pc=0x587867
github.com/go-webgpu/goffi/ffi.CallFunction(...)
	/home/mike/go/pkg/mod/github.com/go-webgpu/goffi@v0.4.2/ffi/ffi.go:267
github.com/gogpu/wgpu/hal/vulkan/vk.(*Commands).GetPhysicalDeviceSurfaceCapabilitiesKHR(0x3b676778e010, 0x7f8a6c0bd230, 0x7f8a6c0976b0, 0x3b67677bc000)
	/home/mike/go/pkg/mod/github.com/gogpu/wgpu@v0.20.1/hal/vulkan/vk/commands_gen.go:2850 +0x126 fp=0x3b676747d910 sp=0x3b676747d8a8 pc=0x595b26
github.com/gogpu/wgpu/hal/vulkan.vkGetPhysicalDeviceSurfaceCapabilitiesKHR(...)
	/home/mike/go/pkg/mod/github.com/gogpu/wgpu@v0.20.1/hal/vulkan/swapchain.go:519
github.com/gogpu/wgpu/hal/vulkan.(*Surface).createSwapchain(0x3b6767798020, 0x3b67677b2000, 0x3b676778a380)
	/home/mike/go/pkg/mod/github.com/gogpu/wgpu@v0.20.1/hal/vulkan/swapchain.go:69 +0xcf fp=0x3b676747dbb8 sp=0x3b676747d910 pc=0x613ccf
github.com/gogpu/wgpu/hal/vulkan.(*Surface).Configure(0x3b6767798020, {0x824050?, 0x3b67677b2000?}, 0x3b676778a380)
	/home/mike/go/pkg/mod/github.com/gogpu/wgpu@v0.20.1/hal/vulkan/api.go:289 +0x24b fp=0x3b676747dca0 sp=0x3b676747dbb8 pc=0x60200b
github.com/gogpu/gogpu.(*Renderer).init(0x3b67677043c0, 0x12?, 0x79?)
	/home/mike/go/pkg/mod/github.com/gogpu/gogpu@v0.23.2/renderer.go:198 +0x6c9 fp=0x3b676747ded0 sp=0x3b676747dca0 pc=0x6d5429
github.com/gogpu/gogpu.newRenderer({0x822c68, 0x3b676765c280}, 0x0, 0x0)
	/home/mike/go/pkg/mod/github.com/gogpu/gogpu@v0.23.2/renderer.go:101 +0x75 fp=0x3b676747def8 sp=0x3b676747ded0 pc=0x6d4cf5
github.com/gogpu/gogpu.(*App).Run.func1()
	/home/mike/go/pkg/mod/github.com/gogpu/gogpu@v0.23.2/app.go:187 +0x35 fp=0x3b676747df30 sp=0x3b676747def8 pc=0x6d0cf5
github.com/gogpu/gogpu.(*App).Run.(*RenderLoop).RunOnRenderThreadVoid.(*Thread).CallVoid.func3()
	/home/mike/go/pkg/mod/github.com/gogpu/gogpu@v0.23.2/internal/thread/thread.go:84 +0x22 fp=0x3b676747df50 sp=0x3b676747df30 pc=0x6d0ca2
github.com/gogpu/gogpu/internal/thread.New.func1()
	/home/mike/go/pkg/mod/github.com/gogpu/gogpu@v0.23.2/internal/thread/thread.go:50 +0x62 fp=0x3b676747dfe0 sp=0x3b676747df50 pc=0x6a6ae2
runtime.goexit({})
	/home/mike/.local/go/src/runtime/asm_amd64.s:1771 +0x1 fp=0x3b676747dfe8 sp=0x3b676747dfe0 pc=0x4894e1
created by github.com/gogpu/gogpu/internal/thread.New in goroutine 1
	/home/mike/go/pkg/mod/github.com/gogpu/gogpu@v0.23.2/internal/thread/thread.go:39 +0xec

I'm using the sway wayland compositor, if that's relevant. Is there any more information that I can give to help with diagnosis?

Is this issue ok here? Or should I raise it in the gogpu/gogpu or gogpu/wgpu repository?

[kolkov]

Thanks for reporting this! You're right that this issue belongs in a different repository — the crash is entirely in the windowing/GPU stack, not in the UI toolkit.

Diagnosis:

The error interface 'xdg_toplevel' has no event 3 is a Wayland protocol version mismatch — Sway's xdg-shell implementation doesn't support the event your client library is sending. The SIGSEGV then occurs in wgpu/hal/vulkan/swapchain.go when vkGetPhysicalDeviceSurfaceCapabilitiesKHR is called on an invalid/partially-initialized surface.

Stack trace summary:

gogpu.App.Run() -> newRenderer() -> Surface.Configure()
  -> Surface.createSwapchain() -> vkGetPhysicalDeviceSurfaceCapabilitiesKHR()
  -> SIGSEGV (null pointer dereference at addr=0x18)

Recommendation: Please re-open this in gogpu/gogpu — that's where the windowing, Wayland surface creation, and Vulkan renderer code lives. Including your Sway version and swaymsg -t get_version output would help with diagnosis.

I'll close this issue here since gogpu/ui doesn't handle windowing or GPU surfaces directly.

[kolkov]

@pekim The fix has been released in two packages:

• gogpu v0.23.3 — fixed xdg_toplevel C interface descriptor (EventCount=2 with Version=6), added full xdg-shell v4/v5 event handling
• wgpu v0.20.2 — added WSI function validation in LoadInstance() as defense-in-depth

Root cause: libwayland couldn't deserialize configure_bounds (v4) and wm_capabilities (v5) events because the descriptor only declared 2 events. On compositors like Sway that send these events, wl_display_roundtrip failed silently, leaving the surface unconfigured, and Vulkan crashed on vkGetPhysicalDeviceSurfaceCapabilitiesKHR.

Please try updating to the new versions and let us know if it resolves the crash on your setup.

[pekim]

Yes those new versions resolve the problem. Thank you for your quick response.