Use C annotations to produce safer Rust

[thedataking]

Attributes such as nonnull, counted_by, sized_by, single, ownership_holds, if present in the source code could be recognized by the transpiler and would ideally enable generation of safer code. For instance, knowing what input parameter counts or sizes a pointer could allow us to emit an array or slice type where we'd normally emit a raw pointer. The single annotation disallows pointer arithmetic.

Useful resources:

• clang docs on bounds annotations
• clang docs on ownership annotations

A separate but important question is how much code uses these attributes in the first place.

[fw-immunant]

One possible implementation strategy for this that I would investigate is extending the Translation's renamer to map decls in a more structured way.

[kkysen]

One possible implementation strategy for this that I would investigate is extending the Translation's renamer to map decls in a more structured way.

How would that work exactly?

I know there's definitely a lot we can improve with the renamer (it doesn't take advantage at all of Rust allowing shadowing, so most renames aren't needed).