[VS Code] ReadMemory request causes cast exception on macOS

I’m issuing a ReadMemory request from a VSCode extension using:

const readMemoryResp = await vscode.debug.activeDebugSession.customRequest('readMemory', { memoryReference: memoryReference, count: count, offset: offset });

It works absolutely fine on Windows. However on macOS (Catalina 10.15.7) the following exception occurs:

“Specified cast is not valid.”

I have traced it to the following line of code:

int hr = ((IDebugMemoryBytesDAP)m_engine).CreateMemoryContext(address, out memoryContext);

in AD7DebugSession.cs in the function GetMemoryContext().

[WardenGnaw]

Yep. This most likely is a bug with mono and how it handles embedded interfaces.

We have not had the chance to test readMemory requests on macOS/Linux.

https://github.com/microsoft/MIEngine/pull/1082 should fix the cast exception, but the cast may still fail in mono. https://github.com/microsoft/MIEngine/pull/1075 is part of the progress to move to .NET Core. It is moving to an SDK styled csproj which should make it easier to convert it from .NET Framework v4.6.2 to .NET Core 5.

[gareth-davies-img]

@WardenGnaw Many thanks for looking at this issue.

We are using VSCode 1.51.1 and cpptools 1.1.2 out the box, so are using the standard cppdbg.ad7Engine.json.

And I can confirm that the same cast exception happens on Linux.