What is rustc_codegen_clr?

NOTE: this project is a very early proof-of-concept This is a compiler backend for rustc which targets the .NET platform and runtime, and could enable compiling rust code for the .NET runtime. This would enable you to use some Rust libraries from C#/F#, with little effort.

.NET runtime has GC, so would not Rusts memory management be useless here?

Rust code usually heavily uses stack instead of Heap. This would speed up code ruining within the CLR runtime too. As for the heap allocated objects, they will be allocated from unmanged(non-GC) memory, and will be allocated/freed exactly like in Rust.

I can already load shared libraries from C# code, so is this not useless? Does this improve interop?

The Rust APIs this codegen exposes to C#/F# code would be only slightly easier to use than something you could expose in a .so or .dll rust library.

Interop would still require some effort, but the Rust code would be bundled together with everything else. You will also have the guarantee that types you use from C# are exactly the same as the ones in C#, preventing any issues coming from such mismatch. All types can be safely send between Rust and C#, with exactly the same layout.

Additionally, since all Rust code compiled with this codegen can be bundled with C#/F# code, you would no longer need to ship different versions of the library for different architectures. Any architecture supported by CLR would work out of the box, without the exact same binary.

You also avoid the cost of switches between code running within the runtime and outside it. While this cost is not something unbearable, it is not something you can easily get rid of, and reducing it has some safety penalties associated with. In this case, all code will run inside the runtime, meaning no transition between code running inside runtime and outside of it will occur.

Compiling Rust to CLR is potentially better for the JIT. Since CLR's JIT now "sees" all the code, it can make better decisions regarding optimization, producing faster code.

Licensing

rustc_codegen_clr is dual licensed under MIT license or Apache License, Version 2.0.

Compatibility?

rustc_codegen_clr is tested solely on Linux x86_64. Anything else should, but does not have to work.

How far is the project along:

Functionality

• Basic functions get translated properly.
• Arithmetic operations work
• Most if's work.
• Basic match works.
• While loops work.
• Calls
• Basic IL optimization.
• Setting value of a reference
• Getting value of a reference
• Creating slices from arrays
• Creating arrays
• Indexing arrays broken
• Getting values of fields
• Setting fields
• Pointer dereferecing
• Basic generics
• for loops

Types

NOTE This section says only if a type can be translated for .NET to understand. This does not mean the type is fully usable.

• All integer and float types are supported.
• Tuples are supported
• References are supported
• Arrays, slices
• Void type
• Combinations of all of the above.
• Structs
• Enums
• Traits Some, not all
• iterators

Issues

The backend is still very much untested and may contain a litany of buggs. The backend crashes any time it encounters something not supported yet.