This guide explains how to build a Rust compiler for use with the Fuchsia. This is useful if you need to build Fuchsia with a patched compiler, or a compiler built with custom options. Building a custom Rust toolchain is not always necessary for building Fuchsia with a different version of Rust; see Build Fuchsia with a custom Rust toolchain for details.
Prior to building a custom Rust toolchain for Fuchsia, you need to do the following:
If you haven‘t already, clone the Rust source. The Guide to Rustc Development is a good resource to reference whenever you’re working on the compiler.
DEV_ROOT={{ '<var>' }}DEV_ROOT{{ '</var> '}} # parent of your Rust directory git clone --recurse-submodules https://github.com/rust-lang/rust.git $DEV_ROOT/rust
Run the following command to install cmake and jq/tomlq:
sudo apt-get install cmake ninja-build jq yq
Run the following command to obtain the infra sources:
DEV_ROOT={{ '<var>' }}DEV_ROOT{{ '</var> '}} # parent of your Rust directory mkdir -p $DEV_ROOT/infra && \ ( \ builtin cd $DEV_ROOT/infra && \ jiri init && \ jiri import -overwrite -name=fuchsia/manifest infra \ https://fuchsia.googlesource.com/manifest && \ jiri update \ )
Note: Running jiri update
from the infra
directory ensures that you have the most recent configurations and tools.
Run the following command to use cipd
to get a Fuchsia core IDK, a Linux sysroot, a recent version of clang, and the correct beta compiler for building Fuchsia's Rust toolchain:
DEV_ROOT={{ '<var>' }}DEV_ROOT{{ '</var>' }} HOST_TRIPLE={{ '<var>' }}x86_64-unknown-linux-gnu{{ '</var>' }} cat << "EOF" > cipd.ensure @Subdir sdk fuchsia/sdk/core/${platform} latest @Subdir sysroot/linux fuchsia/third_party/sysroot/linux git_revision:db18eec0b4f14b6b16174aa2b91e016663157376 @Subdir sysroot/focal fuchsia/third_party/sysroot/focal latest @Subdir clang fuchsia/third_party/clang/${platform} integration EOF STAGE0_DATE=`jq .compiler.date ${DEV_ROOT}/rust/src/stage0.json --raw-output` STAGE0_VERSION=`jq .compiler.version ${DEV_ROOT}/rust/src/stage0.json --raw-output` STAGE0_COMMIT_HASH=`curl -s "https://static.rust-lang.org/dist/${STAGE0_DATE}/channel-rust-${STAGE0_VERSION}.toml" | tomlq .pkg.rust.git_commit_hash --raw-output` echo "@Subdir stage0" >> cipd.ensure echo "fuchsia/third_party/rust/host/\${platform} git_revision:${STAGE0_COMMIT_HASH}" >> cipd.ensure echo "fuchsia/third_party/rust/target/${HOST_TRIPLE} git_revision:${STAGE0_COMMIT_HASH}" >> cipd.ensure $DEV_ROOT/infra/fuchsia/prebuilt/tools/cipd ensure --root $DEV_ROOT --ensure-file cipd.ensure
Note: these versions are not pinned, so every time you run the cipd ensure
command, you will get an updated version. As of writing, however, this matches the recipe behavior.
Downloading the Fuchsia-built stage0 compiler is optional, but useful for recreating builds in CI. If the stage0 is not available you may instruct the Rust build to download and use the upstream stage0 compiler by omitting those lines from your cipd.ensure
file and removing the --stage0
arguments to generate_config.py
below.
Change into your Rust directory.
Run the following command to generate a configuration for the Rust toolchain:
DEV_ROOT={{ '<var>' }}DEV_ROOT{{ '</var>' }} $DEV_ROOT/infra/fuchsia/prebuilt/tools/vpython3 \ $DEV_ROOT/infra/fuchsia/recipes/recipes/rust_toolchain.resources/generate_config.py \ config_toml \ --clang-prefix=$DEV_ROOT/clang \ --host-sysroot=$DEV_ROOT/sysroot/linux \ --stage0=$DEV_ROOT/stage0 \ --prefix=$(pwd)/install/fuchsia-rust \ | tee fuchsia-config.toml $DEV_ROOT/infra/fuchsia/prebuilt/tools/vpython3 \ $DEV_ROOT/infra/fuchsia/recipes/recipes/rust_toolchain.resources/generate_config.py \ environment \ --eval \ --clang-prefix=$DEV_ROOT/clang \ --sdk-dir=$DEV_ROOT/sdk \ --stage0=$DEV_ROOT/stage0 \ --linux-sysroot=$DEV_ROOT/sysroot/linux \ --linux-riscv64-sysroot=$DEV_ROOT/sysroot/focal \ | tee fuchsia-env.sh
(Optional) Run the following command to tell git to ignore the generated files:
echo fuchsia-config.toml >> .git/info/exclude echo fuchsia-env.sh >> .git/info/exclude
(Optional) Customize fuchsia-config.toml
.
Change into your Rust source directory.
Run the following command to build and install Rust plus the Fuchsia runtimes spec:
DEV_ROOT={{ '<var>' }}DEV_ROOT{{ '</var>' }} rm -rf install/fuchsia-rust mkdir -p install/fuchsia-rust # Copy and paste the following subshell to build and install Rust, as needed. # The subshell avoids polluting your environment with fuchsia-specific rust settings. ( source fuchsia-env.sh && ./x.py install --config fuchsia-config.toml \ --skip-stage0-validation ) && \ rm -rf install/fuchsia-rust/lib/.build-id && \ $DEV_ROOT/infra/fuchsia/prebuilt/tools/vpython3 \ $DEV_ROOT/infra/fuchsia/recipes/recipes/rust_toolchain.resources/generate_config.py \ runtime \ | $DEV_ROOT/infra/fuchsia/prebuilt/tools/vpython3 \ $DEV_ROOT/infra/fuchsia/recipes/recipe_modules/toolchain/resources/runtimes.py \ --dir install/fuchsia-rust/lib \ --dist dist \ --readelf fuchsia-build/host/llvm/bin/llvm-readelf \ --objcopy fuchsia-build/host/llvm/bin/llvm-objcopy \ > install/fuchsia-rust/lib/runtime.json
If you want to skip the install step, for instance during development of Rust itself, you can do so with the following command.
( source fuchsia-env.sh && ./x.py build --config fuchsia-config.toml \ --skip-stage0-validation )
If you are getting build errors, try deleting the Rust build directory:
rm -rf fuchsia-build
Then re-run the command to build Rust.
With a newly compiled custom Rust toolchain, you're ready to use it to build Fuchsia. Directions on how to do so are available in a dedicated guide.