Rust with AVR support

This project adds support for the AVR microcontroller to Rust.

Caveats

Some parts of libcore are disabled via substituting the functions in the original API with empty functions
- This is done because several bugs cause certain functions to trigger bugs in the AVR LLVM backend
- Missing functionality includes
  - Crucial core::fmt functions are stubbed out, causing empty results (avr-rust/libcore#3)
  - The entire core::sync module is missing (avr-rust/libcore#1)
  - All mentions of 128-bit integers are removed from libcore (avr-rust/libcore#5)
  - Panics currently trigger infinite loops with no message (avr-rust/libcore#4)

Building and installation

This will compile Rust with AVR support. This will not create a fully-fledged cross-compiler, however, as it does not compile any libraries such as libcore or liblibc. To do this, the --target=avr-unknown-unknown flag must be passed to configure, which is not fully supported yet due to bugs.

# Grab the avr-rust sources
git clone https://github.com/avr-rust/rust.git

# Create a directory to place built files in
mkdir build && cd build

# Generate Makefile using settings suitable for an experimental compiler
../rust/configure \
  --enable-debug \
  --disable-docs \
  --enable-llvm-assertions \
  --enable-debug-assertions \
  --enable-optimize \
  --prefix=/opt/avr-rust

# Build the compiler, optionally install it to /opt/avr-rust
make
make install

# Register the toolchain with rustup
rustup toolchain link avr-toolchain $(realpath $(find . -name 'stage1'))

# Optionally enable the avr toolchain globally
rustup default avr-toolchain

Usage

With Xargo (recommended)

Take a look at the example blink program.

Vanilla `rustc`

AVR support is enabled by passing the --target avr-unknown-unknown flag to rustc.

Note that the Rust libcore library (essentially required for every Rust program), must be manually compiled for it to be used, as it will not be built for AVR during compiler compilation (yet). Work is currently being done in order to allow libcore to be automatically compiled for AVR.