Hello,
We encountered a crash during the garbage collection phase when using sequencer conditions with subsequence tracks. Specifically, objects appear to break the “Disregard for GC” assumptions. This issue occurs only in builds, not in the editor.
Attached are the crash log, a test project, and its build to help reproduce the issue.
If there are any relevant Change Lists (CLs) addressing this problem, could you kindly share them?
Thank you for your assistance!
Regards,
Igor
Steps to Reproduce
Hey Igor,
Which version of the engine are you on? Your repro project does not repro on latest release and knowing the exact engine would help narrow this down for you.
That said this is most likely related to a fix that was made in the 5.5.4 hotfix.
https://github.com/EpicGames/UnrealEngine/commit/ca064b4af696028784e897f9018da847a237742d or CL: 39917814 in P4.
Hi Dustin,
Thanks for following up!
We are on Unreal Engine 5.5.4, and the mentioned CL: 39917814 is already present in our codebase.
We’ve tested both our Perforce build and the Launcher build, and the crash still occurs in both cases. The ConditionsTest project was created using the Launcher version of the engine.
As noted in our initial report, the crash happens only in builds, not in the editor, during the garbage collection phase when using sequencer conditions with subsequence tracks, seemingly breaking the “Disregard for GC” assumptions.
Appreciate any insights you might have! Let us know if there’s anything else we can provide to help narrow this down.
Best,
Igor
Hey Igor,
Thanks for your patience, and thank you for raising this. I’ve logged a bug that you can follow along with,
https://issues.unrealengine.com/issue/UE-265587, it can take 24 hours or so for the bug to show up in the issue tracker.
The primary issue is that the conditions get hard referenced and tracked in the MovieSceneCompiledDataManager.hierarchy stack for other reasons; when you destroy the level sequence actor, the conditions inside will cause a crash.
You can try making FMovieSceneSubSequenceData.Condition a TWeakObjectPtr, and then fix up FSequenceUpdater_Hierarchical::Update’s reference to it to address the bug.
Unfortunately, though I don’t have any other options to address the bug.