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The Rust Programming Language for Espressif chips

This fork enables projects to be built for the Xtensa-based ESP32, ESP32-SXX and ESP8266 using Espressif's llvm fork. (RiscV chips like ESP32-CXX are already supported in stock Rust.)

Moreover, this fork enables Rust STD support (networking, threads, and filesystem) for all chips in the ESP32 family (Xtensa and RiscV), by optionally linking with the ESP-IDF framework.

The esp-rs organization has been formed to develop runtime, pac and hal crates for the Espressif chips (bare-metal as well as ESP-IDF based).

Join in on the discussion:!


Espressif offers pre-built binaries of this fork. Follow the instructions for your operating system.


Install Rustup.

Build using these steps:

$ git clone
$ cd rust
$ git checkout esp
$ ./configure --experimental-targets=Xtensa
$ ./ build --stage 2
  • NOTE 1: Building might take close to an hour
  • NOTE 2: Make sure you are using the esp GIT branch of the fork (the default)
  • NOTE 3: Do NOT rename the directory ('rust') where you've cloned the Rust fork. It must be 'rust' or you might have strange issues later on when using it. You can however place it anywhere in your file tree

Fix toolchain vendor/ directory, so that building STD with Cargo does work

(Assuming you are still in the rust/ directory):

$ mkdir vendor
$ cd vendor
$ ln -s ../library/rustc-std-workspace-alloc/ rustc-std-workspace-alloc
$ ln -s ../library/rustc-std-workspace-core/ rustc-std-workspace-core
$ ln -s ../library/rustc-std-workspace-std/ rustc-std-workspace-std

Make Rustup aware of the newly built compiler:

$ rustup toolchain link esp ~/<...>/rust/build/x86_64-unknown-linux-gnu/stage2

Switch to the new compiler in Rustup:

$ rustup default esp

Check the compiler:

$ rustc --print target-list

At the end of the printed list of targets you should see:


Building LLVM clang

You'll need the custom LLVM clang based on the Espressif LLVM fork for Rust STD support. Build as follows:

$ git clone
$ cd llvm-project
$ mkdir build
$ cd build
$ cmake -G Ninja -DLLVM_ENABLE_PROJECTS='clang' -DCMAKE_BUILD_TYPE=Release ../llvm
$ cmake --build .
$ export PATH=`pwd`/bin:$PATH

Check that you have the custom clang on your path:

$ which clang
$ which llvm-config

The above should output locations pointing at your custom-built clang toolchain.

  • NOTE 1: Building LLVM clang might take even longer time than building the Rustc toolchain
  • NOTE 2: You might want to make the PATH modification step from above permanent. Please make sure that the custom Clang compiler is the first on your PATH so that it takes precedence over any clang compiler you might have installed using your distro / OS

Updating this fork

The patch set can be found here. Checkout from upstream/master, apply the patches on at a time using git am -3 < path/to/patch.patch, fixing any conflicts if necessary (remember to PR the changes back to the patches repo). Once it builds submit a PR against this repo with the branch name esp-update-$DATE.

If the llvm submodule needs to be updated, the following should work:

git submodule set-url src/llvm-project
git submodule set-branch -b $BRANCH_NAME src/llvm-project
git submodule update --init --recursive --remote src/llvm-project

Once accepted, the new branch will be renamed esp-target, hence making it the default. Don't worry about the README changes, I will port those across once I accept the PR.

This is the main source code repository for Rust. It contains the compiler, standard library, and documentation.

Note: this README is for users rather than contributors. If you wish to contribute to the compiler, you should read the Getting Started of the rustc-dev-guide instead of this section.

Quick Start

Read "Installation" from The Book.

Installing from Source

The Rust build system uses a Python script called to build the compiler, which manages the bootstrapping process. It lives in the root of the project.

The command can be run directly on most systems in the following format:

./ <subcommand> [flags]

This is how the documentation and examples assume you are running

Systems such as Ubuntu 20.04 LTS do not create the necessary python command by default when Python is installed that allows to be run directly. In that case you can either create a symlink for python (Ubuntu provides the python-is-python3 package for this), or run using Python itself:

# Python 3
python3 <subcommand> [flags]

# Python 2.7
python2.7 <subcommand> [flags]

More information about can be found by running it with the --help flag or reading the rustc dev guide.

Building on a Unix-like system

  1. Make sure you have installed the dependencies:

    • g++ 5.1 or later or clang++ 3.5 or later
    • python 3 or 2.7
    • GNU make 3.81 or later
    • cmake 3.4.3 or later
    • ninja
    • curl
    • git
    • ssl which comes in libssl-dev or openssl-devel
    • pkg-config if you are compiling on Linux and targeting Linux
  2. Clone the source with git:

    $ git clone
    $ cd rust
  1. Configure the build settings:

    The Rust build system uses a file named config.toml in the root of the source tree to determine various configuration settings for the build. Copy the default config.toml.example to config.toml to get started.

    $ cp config.toml.example config.toml

    If you plan to use install to create an installation, it is recommended that you set the prefix value in the [install] section to a directory.

    Create install directory if you are not installing in default directory

  2. Build and install:

    $ ./ build && ./ install

    When complete, ./ install will place several programs into $PREFIX/bin: rustc, the Rust compiler, and rustdoc, the API-documentation tool. This install does not include Cargo, Rust's package manager. To build and install Cargo, you may run ./ install cargo or set the build.extended key in config.toml to true to build and install all tools.

Building on Windows

There are two prominent ABIs in use on Windows: the native (MSVC) ABI used by Visual Studio, and the GNU ABI used by the GCC toolchain. Which version of Rust you need depends largely on what C/C++ libraries you want to interoperate with: for interop with software produced by Visual Studio use the MSVC build of Rust; for interop with GNU software built using the MinGW/MSYS2 toolchain use the GNU build.


MSYS2 can be used to easily build Rust on Windows:

  1. Grab the latest MSYS2 installer and go through the installer.

  2. Run mingw32_shell.bat or mingw64_shell.bat from wherever you installed MSYS2 (i.e. C:\msys64), depending on whether you want 32-bit or 64-bit Rust. (As of the latest version of MSYS2 you have to run msys2_shell.cmd -mingw32 or msys2_shell.cmd -mingw64 from the command line instead)

  3. From this terminal, install the required tools:

    # Update package mirrors (may be needed if you have a fresh install of MSYS2)
    $ pacman -Sy pacman-mirrors
    # Install build tools needed for Rust. If you're building a 32-bit compiler,
    # then replace "x86_64" below with "i686". If you've already got git, python,
    # or CMake installed and in PATH you can remove them from this list. Note
    # that it is important that you do **not** use the 'python2', 'cmake' and 'ninja'
    # packages from the 'msys2' subsystem. The build has historically been known
    # to fail with these packages.
    $ pacman -S git \
                make \
                diffutils \
                tar \
                mingw-w64-x86_64-python \
                mingw-w64-x86_64-cmake \
                mingw-w64-x86_64-gcc \
  4. Navigate to Rust's source code (or clone it), then build it:

    $ ./ build && ./ install


MSVC builds of Rust additionally require an installation of Visual Studio 2017 (or later) so rustc can use its linker. The simplest way is to get the Visual Studio, check the “C++ build tools” and “Windows 10 SDK” workload.

(If you're installing cmake yourself, be careful that “C++ CMake tools for Windows” doesn't get included under “Individual components”.)

With these dependencies installed, you can build the compiler in a cmd.exe shell with:

> python build

Currently, building Rust only works with some known versions of Visual Studio. If you have a more recent version installed and the build system doesn't understand, you may need to force rustbuild to use an older version. This can be done by manually calling the appropriate vcvars file before running the bootstrap.

> CALL "C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Auxiliary\Build\vcvars64.bat"
> python build

Specifying an ABI

Each specific ABI can also be used from either environment (for example, using the GNU ABI in PowerShell) by using an explicit build triple. The available Windows build triples are:

  • GNU ABI (using GCC)
    • i686-pc-windows-gnu
    • x86_64-pc-windows-gnu
  • The MSVC ABI
    • i686-pc-windows-msvc
    • x86_64-pc-windows-msvc

The build triple can be specified by either specifying --build=<triple> when invoking commands, or by copying the config.toml file (as described in Installing From Source), and modifying the build option under the [build] section.

Configure and Make

While it's not the recommended build system, this project also provides a configure script and makefile (the latter of which just invokes

$ ./configure
$ make && sudo make install

When using the configure script, the generated file may override the config.toml file. To go back to the config.toml file, delete the generated file.

Building Documentation

If you’d like to build the documentation, it’s almost the same:

$ ./ doc

The generated documentation will appear under doc in the build directory for the ABI used. I.e., if the ABI was x86_64-pc-windows-msvc, the directory will be build\x86_64-pc-windows-msvc\doc.


Since the Rust compiler is written in Rust, it must be built by a precompiled "snapshot" version of itself (made in an earlier stage of development). As such, source builds require a connection to the Internet, to fetch snapshots, and an OS that can execute the available snapshot binaries.

Snapshot binaries are currently built and tested on several platforms:

Platform / Architecture x86 x86_64
Windows (7, 8, 10, ...)
Linux (kernel 2.6.32, glibc 2.11 or later)
macOS (10.7 Lion or later) (*)

(*): Apple dropped support for running 32-bit binaries starting from macOS 10.15 and iOS 11. Due to this decision from Apple, the targets are no longer useful to our users. Please read our blog post for more info.

You may find that other platforms work, but these are our officially supported build environments that are most likely to work.

Getting Help

The Rust community congregates in a few places:


If you are interested in contributing to the Rust project, please take a look at the Getting Started guide in the rustc-dev-guide.


Rust is primarily distributed under the terms of both the MIT license and the Apache License (Version 2.0), with portions covered by various BSD-like licenses.



The Rust Foundation owns and protects the Rust and Cargo trademarks and logos (the “Rust Trademarks”).

If you want to use these names or brands, please read the media guide.

Third-party logos may be subject to third-party copyrights and trademarks. See Licenses for details.


Rust for the xtensa architecture. Built in targets for the ESP32 and ESP8266



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