ComLightInterop

I’ve been writing C++ COM objects for use in .NET for years now. Some are for performance-critical parts, like manually vectorized SIMD code. Another use case is interop heavy code, using Direct3D, media foundation, Eigen, other C and C++ libraries. It works even on Linux https://github.com/Const-me/ComLightInterop I also have these parts, especially about the interop. Libraries like drm, kms, gles, udev, and many other kernel APIs are only usable from C or C++. Had very few issues with IUnknown-based interop. On Linux, my interop library retains .NET objects with GCHandle while they are referenced by C++ code. On Windows, it’s done automatically by the runtime. C++ implemented objects are automatically retained on both OSes. What exactly do you think is a hard problem about such interop? Leaks due to ref.count cycles are possible, but I’

If you can read C#, maybe this will help: https://github.com/Const-me/ComLightInterop Specifically, this class implementing vtable callable from C++: https://github.com/Const-me/ComLightInterop/blob/master/ComL... About multiple interfaces, all of them need 3 first vtable entries pointing to the 3 IUnknown methods. Also, don't forget that when client calls QueryInterface on any interface of the same object with IID_IUnknown argument, you must return same IUnknown pointer. Some parts of COM use that pointer as object's identity.

Also COM ABI is really small, easily portable to other OSes. I’ve recently ported to Linux and implemented .NET core interop. The C++ runtime is just a couple pages of code. https://github.com/Const-me/ComLightInterop