This callstack is occurring in 4.17.0 and 4.17.1, and appears to be a continuation of [Link Removed], which was fixed in 4.16.2 with CL 3502786.
I'm not re-opening [Link Removed] because there are no reports of the crash occurring in 4.16.2; but they reappeared in the next release. One example: [Link Removed]
repro steps currently unknown
Assertion failed: !IsLoading() [File:D:\Build\++UE4+Release-4.17+Compile\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\GarbageCollection.cpp] [Line: 1303] UE4Editor_CoreUObject!CollectGarbageInternal() garbagecollection.cpp:1306 UE4Editor_CoreUObject!CollectGarbage() garbagecollection.cpp:1533 UE4Editor_UnrealEd!FEditorFileUtils::SaveDirtyPackages() filehelpers.cpp:2974 UE4Editor_MainFrame!FMainFrameHandler::CanCloseEditor() mainframehandler.h:145 UE4Editor_MainFrame!FMainFrameHandler::CloseRootWindowOverride() mainframehandler.h:164 UE4Editor_SlateCore!SWindow::RequestDestroyWindow() swindow.cpp:1193 UE4Editor_Slate!FSlateApplication::OnWindowClose() slateapplication.cpp:6620 UE4Editor_Core!FWindowsApplication::ProcessDeferredMessage() windowsapplication.cpp:1930 UE4Editor_Core!FWindowsApplication::ProcessDeferredEvents() windowsapplication.cpp:2186 UE4Editor_Slate!FSlateApplication::TickPlatform() slateapplication.cpp:1621 UE4Editor_Slate!FSlateApplication::Tick() slateapplication.cpp:1591 UE4Editor_UnrealEd!TickSlate() feedbackcontexteditor.cpp:362 UE4Editor_UnrealEd!FFeedbackContextEditor::StartSlowTask() feedbackcontexteditor.cpp:442 UE4Editor_Core!FSlowTask::MakeDialog() slowtask.cpp:111 UE4Editor_Engine!FStaticMeshStatusMessageContext::FStaticMeshStatusMessageContext() staticmesh.cpp:1096 UE4Editor_Engine!FStaticMeshRenderData::Cache() staticmesh.cpp:1280 UE4Editor_Engine!UStaticMesh::CacheDerivedData() staticmesh.cpp:2201 UE4Editor_Engine!UStaticMesh::PostLoad() staticmesh.cpp:2565 UE4Editor_CoreUObject!UObject::ConditionalPostLoad() obj.cpp:991 UE4Editor_Engine!UBodySetup::PostLoad() bodysetup.cpp:1179 UE4Editor_CoreUObject!UObject::ConditionalPostLoad() obj.cpp:991 UE4Editor_CoreUObject!EndLoad() uobjectglobals.cpp:1567 UE4Editor_CoreUObject!LoadPackageInternal() uobjectglobals.cpp:1312 UE4Editor_CoreUObject!LoadPackage() uobjectglobals.cpp:1409 UE4Editor_CoreUObject!ResolveName() uobjectglobals.cpp:781 UE4Editor_CoreUObject!StaticLoadObjectInternal() uobjectglobals.cpp:869 UE4Editor_CoreUObject!StaticLoadObject() uobjectglobals.cpp:936 UE4Editor_UnrealEd!FAssetData::GetAsset() assetdata.h:276 UE4Editor_UnrealEd!FAssetDragDropOp::Init() assetdragdropop.cpp:218 UE4Editor_UnrealEd!FAssetDragDropOp::New() assetdragdropop.cpp:49 UE4Editor_ContentBrowser!SAssetView::OnDraggingAssetItem() sassetview.cpp:3906 UE4Editor_ContentBrowser!TMemberFunctionCaller<SAssetView,FReply() delegateinstanceinterface.h:165 UE4Editor_ContentBrowser!UE4Tuple_Private::TTupleImpl<TIntegerSequence<unsigned int> >::ApplyAfter<TMemberFunctionCaller<SAssetView,FReply() tuple.h:497 UE4Editor_ContentBrowser!TBaseSPMethodDelegateInstance<0,SAssetView,0,FReply __cdecl() delegateinstancesimpl.h:327 UE4Editor_ContentBrowser!TBaseDelegate<FReply,FGeometry const & __ptr64,FPointerEvent const & __ptr64>::Execute() delegatesignatureimpl.inl:537 UE4Editor_ContentBrowser!STableRow<TSharedPtr<FAssetViewItem,0> >::OnDragDetected() stablerow.h:589 UE4Editor_Slate!<lambda_3d2f0c0de9bfb1f26dd3fbfeef226ad5>::operator() slateapplication.cpp:5347 UE4Editor_Slate!FEventRouter::Route<FReply,FEventRouter::FDirectPolicy,FPointerEvent,<lambda_3d2f0c0de9bfb1f26dd3fbfeef226ad5> >() slateapplication.cpp:232 UE4Editor_Slate!FSlateApplication::RoutePointerMoveEvent() slateapplication.cpp:5345 UE4Editor_Slate!FSlateApplication::ProcessMouseMoveEvent() slateapplication.cpp:5905 UE4Editor_Slate!FSlateApplication::OnMouseMove() slateapplication.cpp:5839 UE4Editor_Core!FWindowsApplication::ProcessDeferredMessage() windowsapplication.cpp:1756 UE4Editor_Core!FWindowsApplication::DeferMessage() windowsapplication.cpp:2161 UE4Editor_Core!FWindowsApplication::ProcessMessage() windowsapplication.cpp:881 UE4Editor_Core!FWindowsApplication::AppWndProc() windowsapplication.cpp:721 user32!UserCallWinProcCheckWow() user32!DispatchMessageWorker() UE4Editor_Core!FWindowsPlatformMisc::PumpMessages() windowsplatformmisc.cpp:1009 UE4Editor!FEngineLoop::Tick() launchengineloop.cpp:3151 UE4Editor!GuardedMain() launch.cpp:166 UE4Editor!GuardedMainWrapper() launchwindows.cpp:134 UE4Editor!WinMain() launchwindows.cpp:210 UE4Editor!__scrt_common_main_seh() exe_common.inl:253 kernel32!BaseThreadInitThunk() ntdll!RtlUserThreadStart()
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