prysm-pulse/tools/cross-toolchain/README.md

Multiarch Cross Compiling Toolchain

Toolchain suite

This package declares a c++ toolchain suite with cross compilers for targeting five platforms:

• linux_amd64
• linux_arm64
• osx_amd64
• osx_arm64
• windows_amd64

This toolchain suite describes cross compile configuration with a Dockerfile with the appropriate host dependencies. These toolchains can be used locally (see caveats), Remote Build Execution (RBE), and in a docker sandbox (like RBE, but local).

Updating the toolchain suite

1. Build and push the worker docker image, if necessary.

docker build -t gcr.io/prysmaticlabs/rbe-worker:latest tools/cross-toolchain/.
docker push gcr.io/prysmaticlabs/rbe-worker:latest 

Note: You must configured your gcr access credentials to push to gcr.io/prysmaticlabs. Run gcloud auth configure-docker or contact SRE team for push access.

2. Note the docker image sha256 digest from the recently pushed image or use the latest one available.

3. Download and run rbe_configs_gen CLI tool.

# Run from the root of the Prysm repo.
rbe_configs_gen \
  --bazel_version=$(cat .bazelversion) \
  --target_os=linux \
  --exec_os=linux \
  --output_src_root=tools/cross-toolchain/configs \
  --generate_cpp_configs=true \
  --generate_java_configs=true \
  --cpp_env_json=tools/cross-toolchain/cpp_env_clang.json \
  --toolchain_container=gcr.io/prysmaticlabs/rbe-worker@sha256:90d490709a0fb0c817569f37408823a0490e5502cbecc36415caabfc36a0c2e8 # The sha256 digest from step 2.

4. Test the builds work locally for all supported platforms.

bazel build --config=release --config=linux_amd64 --config=llvm //cmd/beacon-chain //cmd/validator //cmd/client-stats //cmd/prysmctl
bazel build --config=release --config=linux_arm64_docker //cmd/beacon-chain //cmd/validator //cmd/client-stats //cmd/prysmctl
bazel build --config=release --config=osx_amd64_docker //cmd/beacon-chain //cmd/validator //cmd/client-stats //cmd/prysmctl
bazel build --config=release --config=osx_arm64_docker //cmd/beacon-chain //cmd/validator //cmd/client-stats //cmd/prysmctl 
bazel build --config=release --config=windows_amd64_docker //cmd/beacon-chain //cmd/validator //cmd/client-stats //cmd/prysmctl

5. Run gazelle.

bazel run //:gazelle

6. Add and commit the newly generated configs.

7. Done!

Cross compile target support

target	linux_amd64	linux_arm64	osx_amd64	osx_arm64	windows_amd64
//beacon-chain	✔️ docker-sandbox and RBE, supported locally only	✔️ docker-sandbox and RBE	✔️ docker-sandbox	✔️ docker-sandbox	✔️ docker-sandbox
//validator	✔️ docker-sandbox and RBE	✔️ docker-sandbox and RBE	✔️ docker-sandbox	✔️ docker-sandbox	✔️

The configurations above are enforced via pull request presubmit checks.

Bazel config flag values

Use these values with --config=<flag>, multiple times if more than one value is defined in the table. Example: bazel build //beacon-chain --config=windows_amd64_docker to build windows binary in a docker sandbox.

Config	linux_amd64	linux_arm64	osx_amd64	osx_arm64	windows_amd64
Local run	linux_amd64	linux_arm64	osx_amd64	osx_arm64	windows_amd64
Docker sandbox	linux_amd64_docker	linux_arm64_docker	osx_amd64_docker	osx_arm64_docker	windows_amd64_docker
RBE (See Caveats)	linux_amd64 and remote	linux_arm64 and remote	osx_amd64 and remote	osx_arm64 and remote	windows_amd64 and remote

Caveats

There are a few caveats to each of these strategies.

• Local runs require clang compiler and the appropriate cross compilers installed. These runs should only be considered for a power user or user with specific build requirements. See the Dockerfile setup scripts to understand what dependencies must be installed and where.
• Docker sandbox is slow. Like really slow! The purpose of the docker sandbox is to test RBE builds without deploying a full RBE system. Each build action is executed in its own container. Given the large number of small targets in this project, the overhead of creating docker containers makes this strategy the slowest of all, but requires zero additional setup.
• Remote Build Execution is by far the fastest, if you have a RBE backend available. This is another advanced use case which will require two config flags above as well as additional flags to specify the --remote_executor. Some of these flags are present in the project .bazelrc with example values, but commented out.