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Experimental rules for the experimental Carbon language

This repository exposes carbon_binary to run Carbon files.

Since Carbon does not have a compiler yet, the carbon_binary target is a shell wrapper around the proof-of-concept Carbon explorer. It is also only able to take in a single source file as input.

Planned features

  • A full Carbon toolchain, as soon as a lowering to some form of processable IR (probably LLVM IR) exists.
  • carbon_library, as soon as import is usable.
  • Carbon-C++ interop with the toolchains in rules_ll, as soon as this is feature is implemented.

Quickstart

Install bazelisk.

Execute the following commands in an empty directory to set up a Bazel module capable of using carbon_binary:

touch WORKSPACE.bazel .bazelrc
echo cbb4eb1973a7fb49d15ced3fea6498f714f3ab0c > .bazelversion
echo 'bazel_dep(name="rules_carbon", version="20220727.0")' > MODULE.bazel

Note that we use CI images of Bazel here because the prereleases do not include the bugfixes we need.

Copy the following lines into the just created .bazelrc file:

# Upstream LLVM/Clang requires C++17. This will only configure rules_cc.
build --repo_env=BAZEL_CXXOPTS='-std=c++17'
run --repo_env=BAZEL_CXXOPTS='-std=c++17'

# Separate the toolchain from regular code. This will put execution artifacts
# into bazel-out/ll_linux_exec_platform-opt-exec-<hash>.
build --experimental_platform_in_output_dir
run --experimental_platform_in_output_dir

# We require bzlmod.
build --experimental_enable_bzlmod
run --experimental_enable_bzlmod

# We use a custom registry.
build --registry=https://raw.githubusercontent.com/eomii/bazel-eomii-registry/main/
run --registry=https://raw.githubusercontent.com/eomii/bazel-eomii-registry/main/

# Hash diff (baseline config, transition config) in bazel-out directory names.
build --experimental_output_directory_naming_scheme=diff_against_baseline
run --experimental_output_directory_naming_scheme=diff_against_baseline

# Exec configuration handled by experimental_output_directory_layout.
build --experimental_exec_configuration_distinguisher=off
run --experimental_exec_configuration_distinguisher=off

You can now load the carbon_binary rule definition in your BUILD.bazel files. For instance:

load("@rules_carbon//carbon:defs.bzl", "carbon_binary")

carbon_binary(
   name = "hello_world",
   srcs = ["hello_world.carbon"],
   # Uncomment the setting below to see fancy parser output.
   # This setting is also enabled by running with --compilation_mode=dbg.
   # interpreter_flags = [
   #     "--parser_debug",
   # ]
)

See rules_carbon/examples for full examples.

Contributing

Before you send a PR, install the pre-commit hooks:

pip install pre-commit
pre-commit install

and verify that all tools pass without failure on the entire repository:

pre-commit run --all-files

License

Copyright 2022 eomii, distributed under the Apache 2.0 License.

The maintainers of rules_carbon absolutely love the Carbon project, but are not affiliated with it in any way.