System.ExecutionEngineException

[azchohfi]

HResult=0x80131506

>	System.Private.CoreLib.dll!System.Runtime.InteropServices.Marshal.PtrToStructureHelper(System.IntPtr ptr, System.Type structureType) Line 203	C#
 	System.Private.CoreLib.dll!System.Runtime.InteropServices.Marshal.PtrToStructure(System.IntPtr ptr, System.Type structureType) Line 560	C#
 	System.Private.CoreLib.dll!System.Runtime.InteropServices.Marshal.PtrToStructure<WinRT.Interop.IUnknownVftbl>(System.IntPtr ptr) Line 580	C#
 	WinRT.Runtime.dll!WinRT.ObjectReference<WinRT.Interop.IUnknownVftbl>.GetVtables(System.IntPtr thisPtr) Line 210	C#
 	WinRT.Runtime.dll!WinRT.ObjectReference<WinRT.Interop.IUnknownVftbl>.FromAbi(System.IntPtr thisPtr) Line 200	C#
 	WinRT.Runtime.dll!WinRT.MarshalInspectable.FromAbi(System.IntPtr ptr) Line 953	C#
 	WinRT.Runtime.dll!WinRT.MarshalInterface<Windows.Foundation.IAsyncOperation<System.Collections.Generic.IReadOnlyList<Windows.Storage.IStorageItem>>>.FromAbi(System.IntPtr ptr) Line 799	C#
 	Microsoft.Windows.SDK.NET.dll!ABI.Windows.Foundation.AsyncOperationCompletedHandler<System.Collections.Generic.IReadOnlyList<Windows.Storage.IStorageItem>>.Do_Abi_Invoke.AnonymousMethod__0(System.Delegate invoke)	Unknown
 	WinRT.Runtime.dll!WinRT.ComWrappersSupport.MarshalDelegateInvoke<System.Delegate>(System.IntPtr thisPtr, System.Action<System.Delegate> invoke) Line 62	C#
 	Microsoft.Windows.SDK.NET.dll!ABI.Windows.Foundation.AsyncOperationCompletedHandler<System.Collections.Generic.IReadOnlyList<Windows.Storage.IStorageItem>>.Do_Abi_Invoke(void* thisPtr, System.IntPtr asyncInfo, Windows.Foundation.AsyncStatus asyncStatus)	Unknown

Which happened with this source:

var proxyType = Microsoft.UI.Xaml.VerticalAlignment.Center;
var assembly = proxyType.GetType().GetTypeInfo().Assembly;

foreach (var typeInfo in assembly.**ExportedTypes**)
...

System.Private.CoreLib.dll!System.Reflection.RuntimeAssembly.GetExportedTypes() Line 192 C#

System.Private.CoreLib.dll!System.Reflection.Assembly.ExportedTypes.get() Line 72 C#
Microsoft.Toolkit.Uwp.SampleApp.dll!Microsoft.Toolkit.Uwp.SampleApp.Sample.LookForTypeByName(string typeName) Line 660 C#
Microsoft.Toolkit.Uwp.SampleApp.dll!Microsoft.Toolkit.Uwp.SampleApp.Sample.PreparePropertyDescriptorAsync() Line 572 C#

[jkoritzinsky]

That stack trace doesn't match up with the provided source. Are you sure you posted the source from the correct thread?

[azchohfi]

I've updated to dotnet core 5.0.100-preview.4.20257.1 and the exception is gone!

[azchohfi]

This code repros it:

            const string _root = "https://api.github.com";
            const string _repoName = "WindowsCommunityToolkit";
            const string _repoOwner = "Microsoft";
            using (var client = new HttpClient())
            {
                client.DefaultRequestHeaders.TryAppendWithoutValidation("User-Agent", "Mozilla/5.0 (Windows NT 10.0; WOW64; Trident/7.0; rv:11.0) like Gecko");

                var uri = $"{_root}/repos/{_repoOwner}/{_repoName}/releases";
                var result = await client.GetStringAsync(new Uri(uri));
            }

This is the stack:

>	System.Private.CoreLib.dll!System.Runtime.InteropServices.Marshal.PtrToStructureHelper(System.IntPtr ptr, System.Type structureType) Line 203	C#
 	System.Private.CoreLib.dll!System.Runtime.InteropServices.Marshal.PtrToStructure(System.IntPtr ptr, System.Type structureType) Line 560	C#
 	System.Private.CoreLib.dll!System.Runtime.InteropServices.Marshal.PtrToStructure<WinRT.Interop.IUnknownVftbl>(System.IntPtr ptr) Line 580	C#
 	winrt.runtime.dll!WinRT.ObjectReference<WinRT.Interop.IUnknownVftbl>.GetVtables(System.IntPtr thisPtr)	Unknown
 	winrt.runtime.dll!WinRT.ObjectReference<WinRT.Interop.IUnknownVftbl>.FromAbi(System.IntPtr thisPtr)	Unknown
 	winrt.runtime.dll!WinRT.MarshalInspectable.FromAbi(System.IntPtr ptr)	Unknown
 	winrt.runtime.dll!WinRT.MarshalInterface<Windows.Foundation.IAsyncOperationWithProgress<string, Windows.Web.Http.HttpProgress>>.FromAbi(System.IntPtr ptr)	Unknown
 	Microsoft.Windows.SDK.NET.dll!ABI.Windows.Foundation.AsyncOperationWithProgressCompletedHandler<string, Windows.Web.Http.HttpProgress>.Do_Abi_Invoke.AnonymousMethod__0(System.Delegate invoke)	Unknown
 	winrt.runtime.dll!WinRT.ComWrappersSupport.MarshalDelegateInvoke<System.Delegate>(System.IntPtr thisPtr, System.Action<System.Delegate> invoke)	Unknown
 	Microsoft.Windows.SDK.NET.dll!ABI.Windows.Foundation.AsyncOperationWithProgressCompletedHandler<string, Windows.Web.Http.HttpProgress>.Do_Abi_Invoke(void* thisPtr, System.IntPtr asyncInfo, Windows.Foundation.AsyncStatus asyncStatus)	Unknown

System.ExecutionEngineException
HResult=0x80131506

[jkoritzinsky]

Thanks for the repro! I'll take a look tomorrow!

My guess is we messed up the refcounting somewhere in the custom Async support and are trying to operate on an already-released object. That's usually the cause of this error.

[jkoritzinsky]

Wait, can you give me the outer wrapper of this code as well that calls this through the Windows APIs? Or preferably a zipped up repro of some source I can build locally?

[jkoritzinsky]

The snippet you've given me looks to be entirely .NET-based C# without any of the WinRT apis, so I don't believe I have enough information to put together a good repro to validate that I fix the bug fully.

[azchohfi]

This is not the System.Net.Http.HttpClient, this is the Windows.Web.Http.HttpClient.
System.Net.Http.HttpClient.HttpClient is working fine, and was my work around to this issue.

[jkoritzinsky]

Thanks for clarifying! I'll take a look and fixing this tomorrow.

[azchohfi]

I've also updated to .net core 5 preview 5 (5.0.100-preview.5.20257.3) and I'm also hitting this with the same code as before. Stack on Worker Thread:

 	[Managed to Native Transition]	
 	System.Private.CoreLib.dll!System.Reflection.RuntimeAssembly.GetExportedTypes()	Unknown
 	System.Private.CoreLib.dll!System.Reflection.Assembly.ExportedTypes.get()	Unknown
>	Microsoft.Toolkit.Uwp.SampleApp.dll!Microsoft.Toolkit.Uwp.SampleApp.Sample.LookForTypeByName(string typeName) Line 671	C#
 	Microsoft.Toolkit.Uwp.SampleApp.dll!Microsoft.Toolkit.Uwp.SampleApp.Sample.PreparePropertyDescriptorAsync() Line 572	C#

Lines of code inside LookForTypeByName method:

            var wuxType = Windows.UI.Input.RadialControllerMenuKnownIcon.InkColor;
            assembly = wuxType.GetType().GetTypeInfo().Assembly;

            foreach (var typeInfo in assembly.ExportedTypes)

Actual thread that throws the exception:

 	System.Private.CoreLib.dll!System.Runtime.InteropServices.Marshal.PtrToStructureHelper(System.IntPtr ptr, System.Type structureType)	Unknown
 	System.Private.CoreLib.dll!System.Runtime.InteropServices.Marshal.PtrToStructure(System.IntPtr ptr, System.Type structureType)	Unknown
 	System.Private.CoreLib.dll!System.Runtime.InteropServices.Marshal.PtrToStructure<WinRT.Interop.IUnknownVftbl>(System.IntPtr ptr)	Unknown
>	WinRT.Runtime.dll!WinRT.ObjectReference<WinRT.Interop.IUnknownVftbl>.GetVtables(System.IntPtr thisPtr) Line 210	C#
 	WinRT.Runtime.dll!WinRT.ObjectReference<WinRT.Interop.IUnknownVftbl>.FromAbi(System.IntPtr thisPtr) Line 200	C#
 	WinRT.Runtime.dll!WinRT.MarshalInspectable.FromAbi(System.IntPtr ptr) Line 953	C#
 	WinRT.Runtime.dll!WinRT.MarshalInterface<Windows.Foundation.IAsyncOperation<System.Collections.Generic.IReadOnlyList<Windows.Storage.IStorageItem>>>.FromAbi(System.IntPtr ptr) Line 799	C#
 	Microsoft.Windows.SDK.NET.dll!ABI.Windows.Foundation.AsyncOperationCompletedHandler<System.Collections.Generic.IReadOnlyList<Windows.Storage.IStorageItem>>.Do_Abi_Invoke.AnonymousMethod__0(System.Delegate invoke)	Unknown
 	WinRT.Runtime.dll!WinRT.ComWrappersSupport.MarshalDelegateInvoke<System.Delegate>(System.IntPtr thisPtr, System.Action<System.Delegate> invoke) Line 62	C#
 	Microsoft.Windows.SDK.NET.dll!ABI.Windows.Foundation.AsyncOperationCompletedHandler<System.Collections.Generic.IReadOnlyList<Windows.Storage.IStorageItem>>.Do_Abi_Invoke(void* thisPtr, System.IntPtr asyncInfo, Windows.Foundation.AsyncStatus asyncStatus)	Unknown

Lines of code of CSWinRT that threw the exception:

        private static unsafe (IUnknownVftbl vftblIUnknown, T vftblT) GetVtables(IntPtr thisPtr)
        {
            var vftblPtr = Unsafe.AsRef<VftblPtr>(thisPtr.ToPointer());
            var vftblIUnknown = Marshal.PtrToStructure<IUnknownVftbl>(vftblPtr.Vftbl);

There is also this other GC Finalizer Thread:

 	[Managed to Native Transition]	
>	WinRT.Runtime.dll!ABI.WinRT.Interop.IContextCallback.ContextCallback(WinRT.Interop.PFNCONTEXTCALL pfnCallback, WinRT.Interop.ComCallData* pParam, System.Guid riid, int iMethod) Line 76	C#
 	WinRT.Runtime.dll!WinRT.ObjectReferenceWithContext<WinRT.IInspectable.Vftbl>.Release() Line 245	C#
 	WinRT.Runtime.dll!WinRT.IObjectReference.Dispose(bool disposing) Line 113	C#
 	WinRT.Runtime.dll!WinRT.IObjectReference.~IObjectReference() Line 50	C#

Running this code:

        public unsafe void ContextCallback(global::WinRT.Interop.PFNCONTEXTCALL pfnCallback, ComCallData* pParam, Guid riid, int iMethod)
        {
            Marshal.ThrowExceptionForHR(_obj.Vftbl.ContextCallback_4(ThisPtr, pfnCallback, pParam, ref riid, iMethod, IntPtr.Zero));
        }

[jkoritzinsky]

I finally got a repro. As we've both discovered, this only repros under a managed debugger.

What's interesting is that the COM object pointer looks completely valid. It's IUnknown vtable is fully intact and in the right place. Something in the marshalling IL stub is causing it to throw an EngineExecutionException. I'm trying to narrow that down now.

[jkoritzinsky]

.NET 5 runtime builds version 5.0.0-preview.6.20262.3 or later have the fix.