[RFC] How can we stabilize the library?

[torfmaster]

Use stable rust

Many crates (like cortex-m, cortex-m-rt etc.) can now be used using only stable features of Rust. As the tock kernel itself is language-agnostic it should be no problem to move libtock-rs to stable rust.

Advantages:

• less effort to adapt libtock-rs to the newest Rust versions
• a more stable api

Disadvantages:

• some things (like inline assembly) may be more difficult to use
• some features may even be unavailable
• tock os kernel and libtock-rs may use different versions

Define a "supported" version of the kernel

libtock-c and libtock-rs tend to diverge. Some drivers are only supported in libtock-c and some examples exist only for libtock-rs. Moreover, the abi was changed in incompatible ways. I have some suggestions (non-exhaustive) here

• tag revisions of libtock-rs when they are tested with the corresponding tock kernel version
• define something like a supported version of "master" as we currently do in the Readme

Stabilize the toolchain

My main tool for testing and developing libtock-rs is the run-example script. However, other boards are (accidentally) not supported. We could

• adapt the script to support all boards
• set up a more fancy toolchain

I'd be interested in your opinions.

[Woyten]

Have you tried removing the feature flags one by one? I did, but I got stuck very early (Don't remember where exactly).

[jrvanwhy]

Off the top of my head, the following two things would get in the way:

• Stable rust does not support #![no_std] binaries yet, as some of the lang items you must implement in a binary are unstable.
• Inline assembly is unstable.

[torfmaster]

I don't know exactly about the details, however, you can build no-std-binaries (which are probably actually libraries) using stable rust and the cortex-m-rt crate. Regarding inline assembly: We are using so little of it, we could link the few lines against an external assembly-file, if we wanted.

[jrvanwhy]

After https://github.com/tock/libtock-rs/pull/380 is merged and Rust ~~1.39.0~~ 1.59.0 is released (which stabilizes asm! and global_asm!), libtock-rs will work on stable Rust.

There are a couple things that will still require a nightly toolchain:

1. cargo miri
2. Providing a global memory allocater. IIRC, this was blocked on https://github.com/rust-lang/rust/issues/66741

[hudson-ayers]

I think that should be Rust 1.59.0

[jrvanwhy]

I think that should be Rust 1.59.0

Good catch, fixed.