Has the thread-safety of Map/Set changed since 4.19?

Development Platform & Builds
, , ,
1

There seems to be a pattern of unsolved bug reports with asserts on Map and/or Set adds recently:

https://www.reddit.com/r/unrealengine/comments/8vkvre/problem_with_async_blueprint_native_events_and/e1odwuu/

and now a third variety that we’re seeing:

Assertion failed: !AllocationFlags[Index] [File:Runtime\Core\Public\Containers/SparseArray.h] [Line: 87]

tracksidegepoc!FDebug::AssertFailed()
tracksidegepoc!TSparseArray<TSetElement<TTuple<UAnimMontage * __ptr64,FAnimMontageInstance * __ptr64> >,TSparseArrayAllocator<FDefaultAllocator,FDefaultBitArrayAllocator> >::AllocateIndex()
tracksidegepoc!TSet<TTuple<UAnimMontage * __ptr64,FAnimMontageInstance * __ptr64>,TDefaultMapHashableKeyFuncs<UAnimMontage * __ptr64,FAnimMontageInstance * __ptr64,0>,FDefaultSetAllocator>::Emplace<TPairInitializer<UAnimMontage * __ptr64 const & __ptr64,FAni()
tracksidegepoc!UAnimInstance::Montage_Play()
tracksidegepoc!UAnimInstance::execMontage_Play()
tracksidegepoc!UFunction::Invoke()
tracksidegepoc!UObject::CallFunction()
tracksidegepoc!UObject::execLet()
tracksidegepoc!UObject::ProcessInternal()
tracksidegepoc!UObject::CallFunction()
tracksidegepoc!UObject::ProcessInternal()
tracksidegepoc!UObject::CallFunction()
tracksidegepoc!UObject::ProcessContextOpcode()
tracksidegepoc!UObject::ProcessInternal()
tracksidegepoc!UFunction::Invoke()
tracksidegepoc!UObject::ProcessEvent()
tracksidegepoc!AActor::ProcessEvent()
tracksidegepoc!FLatentActionManager::TickLatentActionForObject()
tracksidegepoc!FLatentActionManager::ProcessLatentActions()
tracksidegepoc!AActor::Tick()

since we upgraded from 4.19 to 4.21. We’ve only seen it after running overnight, but it doesn’t appear to be a leak or memory issue.

Between the three cases, it’s hard to imagine it could be coincidence. Anyone have an idea? My gut feeling says it’s a concurrency issue.

Edit: I’ve found a very similar bug that was fixed many versions ago:

2

Hello,

We’ve recently made a switch to a new bug reporting method using a more structured form. Please visit the link below for more details and report the issue using the new Bug Submission Form. Feel free to continue to use this thread for community discussion around the issue.

https://epicsupport.force.com/unrealengine/s/

Thanks