This crash occurs when you create a landscape, then create and save a material.
Note The crash does not occur unless a landscape was created first
I came across a couple of crashes revolving around shader compiling manager. I came across UE-39977 a couple of times, but this is the first we have seen this callstack. I also came across some other bugs doing the same kind of saving and painting, working with materials etc, but was never able to get a repro. Those crashes can be found here:
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Not sure if they are related, but was encountered performing the same actions.
This is also a Regression since it does not occur in 4.14.2
Result: The editor crashes
Expected Result: The material is saved and the editor dies not crash
UE4Editor_Engine!FShaderCompilingManager::PropagateMaterialChangesToPrimitives() shadercompiler.cpp:1910 UE4Editor_Engine!FShaderCompilingManager::ProcessCompiledShaderMaps() shadercompiler.cpp:1874 UE4Editor_Engine!FShaderCompilingManager::FinishCompilation() shadercompiler.cpp:2231 UE4Editor_Engine!FMaterialShaderMap::Compile() materialshader.cpp:1421 UE4Editor_Engine!FMaterial::BeginCompileShaderMap() materialshared.cpp:1721 UE4Editor_Engine!FMaterial::CacheShaders() materialshared.cpp:1647 UE4Editor_Engine!FDebugViewModeMaterialProxy::FDebugViewModeMaterialProxy() debugviewmodematerialproxy.cpp:142 UE4Editor_Engine!FDebugViewModeMaterialProxy::AddShader() debugviewmodematerialproxy.cpp:40 UE4Editor_Engine!CompileDebugViewModeShaders() debugviewmodehelpers.cpp:273 UE4Editor_MaterialEditor!FMaterialEditorUtilities::BuildTextureStreamingData() materialeditorutilities.cpp:696 UE4Editor_MaterialEditor!FMaterialEditor::UpdateOriginalMaterial() materialeditor.cpp:1655 UE4Editor_MaterialEditor!FMaterialEditor::SaveAsset_Execute() materialeditor.cpp:949 UE4Editor_UnrealEd!TBaseSPMethodDelegateInstance<0,FAssetEditorToolkit,0,TTypeWrapper<void> __cdecl() delegateinstancesimpl.h:327 UE4Editor_UnrealEd!TBaseSPMethodDelegateInstance<0,FAssetEditorToolkit,0,void __cdecl() delegateinstancesimpl.h:433 UE4Editor_Slate!FUICommandList::ExecuteAction() uicommandlist.cpp:97 UE4Editor_Slate!SToolBarButtonBlock::OnClicked() stoolbarbuttonblock.cpp:305 UE4Editor_Slate!TMemberFunctionCaller<SToolBarButtonBlock,FReply() delegateinstanceinterface.h:165 UE4Editor_Slate!TTupleImpl<TIntegerSequence<unsigned int> >::ApplyAfter<TMemberFunctionCaller<SToolBarButtonBlock,FReply() tuple.h:134 UE4Editor_Slate!TBaseSPMethodDelegateInstance<0,SToolBarButtonBlock,0,FReply __cdecl() delegateinstancesimpl.h:327 UE4Editor_Slate!TBaseDelegate<FReply>::Execute() delegatesignatureimpl.inl:537 UE4Editor_Slate!SButton::OnMouseButtonUp() sbutton.cpp:278 UE4Editor_Slate!<lambda_8d0e9a1da76abd0a756a3a9d775f5ed1>::operator() slateapplication.cpp:5052 UE4Editor_Slate!FEventRouter::Route<FReply,FEventRouter::FToLeafmostPolicy,FPointerEvent,<lambda_8d0e9a1da76abd0a756a3a9d775f5ed1> >() slateapplication.cpp:238 UE4Editor_Slate!FSlateApplication::RoutePointerUpEvent() slateapplication.cpp:5041 UE4Editor_Slate!FSlateApplication::ProcessMouseButtonUpEvent() slateapplication.cpp:5504 UE4Editor_Slate!FSlateApplication::OnMouseUp() slateapplication.cpp:5481 UE4Editor_Core!FWindowsApplication::ProcessDeferredMessage() windowsapplication.cpp:1698 UE4Editor_Core!FWindowsApplication::DeferMessage() windowsapplication.cpp:2120 UE4Editor_Core!FWindowsApplication::ProcessMessage() windowsapplication.cpp:867 UE4Editor_Core!FWindowsApplication::AppWndProc() windowsapplication.cpp:714 user32!<Unknown> user32!<Unknown> UE4Editor_Core!FWindowsPlatformMisc::PumpMessages() windowsplatformmisc.cpp:979 UE4Editor!FEngineLoop::Tick() launchengineloop.cpp:2971 UE4Editor!GuardedMain() launch.cpp:166 UE4Editor!GuardedMainWrapper() launchwindows.cpp:130 UE4Editor!WinMain() launchwindows.cpp:206 UE4Editor!__scrt_common_main_seh() exe_common.inl:264 kernel32!<Unknown> ntdll!<Unknown>
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-40055 in the post.