Support compilation on Linux/MacOS with DirectXShaderCompiler for ID3D12ShaderReflection

[lukedan]

While the rest of DirectX 12 isn't particularly useful on Linux/MacOS, having the ability to retrieve reflection information from DXIL (either compiled in the same application or loaded from the filesystem) would be immensely helpful. In fact, DXC already supports this use case (as documented in this issue: microsoft/DirectXShaderCompiler#6057), where it makes use of a specific commit of DirectX-Headers (980971e835876dc0cde415e8f9bc646e64667bf7). I've been able to reproduce @dafedidi's results by modifying wsl/stubs/rpcndr.h and adding #define interface struct before including d3d12shader.h, and it seems to produce the correct reflection data, at least for descriptor bindings.

What is the reason that DXC uses the particular commit instead of supporting the behavior in DirectX-Headers? Does it have anything to do with the data type discrepancies between Linux/MacOS and Windows (e.g. ULONG)? Does anyone foresee any issues with the current approach that DXC is using, and does it make sense to implement it in this repo? Or are there any plans to separate ID3D12ShaderReflection out and potentially making it a part of DXC?

[jenatali]

You probably want to ask that question on the DXC project?

[lukedan]

The reason that I'm asking the questions here is because any actions items that result from this issue will likely be for this repo. DXC already works; it is this repo that is causing issues for me.