Crash when trying to spawn CineCameraActor (and others) under particular Viewport circumstances

Development Pipeline & Plugins
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1

After debugging this, here’s what I’ve found:

It raises SIGFPE (integer divide by zero) on line 1823 of SceneViewport.cpp, where BufferedSlateHandles and CurrentBufferedTargetIndex are both zero.

Actor spawnings that crash:

- CameraRigRail

- CineCameraActor

- CameraShakeSourceActor

- Checkerboard Actor

But things like a standard mesh or generic actor don’t cause crashes.

OS: Kubuntu 22.04

Nvidia driver: 570.153.02

2

This crash occurs when there are more than one Viewports on launch, and at least one of them is “inactive” or not visible via a docked tab. This also occurs when all the viewports (more than 1) are docked & inactive.

Steps to Reproduce

  1. Launch the Editor for any project, no 3rd party plugins.
  2. Add another window to the same “section” as Viewport 1 (such as the Content Browser). Set it as the active tab, switching away from the main Viewport 1.
  3. Open a second viewport, viewports 2-4 are fair game, and dock it, or make it a separate window (it does not matter).
  4. You should now only have one viewport that is actively visible, and one viewport docked and “inactive.” See attached crash screenshot for an example window layout.
  5. Close UE and reopen, so that it launches into this configuration.
  6. With the “Spawn Actor” menu in the toolbar, try to spawn a CineCameraActor.
  7. Crash.
3

Hi [mention removed]​,

I’ve tested the issue myself and, indeed, it crashed. I tested one of the latest versions of the 5.6 development branch, and it no longer happens; it appears to have been fixed by the development team. Are you interested in having the fix commit so you can integrate it into your local engine? If you want to wait for an official release, this should be added to the 5.6.1 release. But yes, it looks like downloading the latest dev version of the 5.6 branch fixes the issue.

This is the git commit I tested to see if the error was still persistent; it is not the fix commit:

https://github.com/EpicGames/UnrealEngine/commit/59e9ce4a7c4c9b501d1e5f0fd1f6277db8aea1d6

Best,

Joan

4

Fantastic, great to hear!