Fixed Session::queryInterface not returning OK when querying for IUnknown/ISlangUnknown

[PeturDarri]

Hello,

I have been trying to use the Slang Compilation API in C# by interfacing with the COM-lite API.

I've been able to call the API functions by directly interfacing with the vtable in unsafe C#, but for my own sanity, I was trying to use the source generated ComWrappers API introduced in .NET 8 to handle everything for me. However, I kept running into a low-level runtime error when it tries to create a wrapper object for the Slang IGlobalSession object.

After a little digging, I found the issue. The .NET runtime is checking if the Slang IGlobalSession implements IUnknown by calling QueryInterface. IGlobalSession implements ISlangUnknown, which shares the same IID as IUnknown, so it should work, right?

Well, it would if it weren't for this small error in the code:

slang/source/slang/slang.cpp

Line 611 in f3b916e

if (uuid == ISlangUnknown::getTypeGuid() && uuid == IGlobalSession::getTypeGuid())

That && is almost certainly supposed to be ||.

I've built with this change and confirmed it fixes the runtime error and allows me to use Slang in C#.

[CLAassistant]

All committers have signed the CLA.

[csyonghe]

Thank you for getting to the bottom of this!