brainhivenl/bazel-arm-none-eabi

ARM none eabi gcc embedded toolchain for Bazel

The goal of the project is to illustrate how to use a custom arm-none-eabi embedded toolchain with Bazel.

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You can follow the post Bazel for ARM embedded toolchains to get more details about this code.

Features

• Simple integration with WORKSPACE / MODULE [experimental]
• Direct access to gcc tools
• Custom toolchain support
• Remote execution support

Use the toolchain from this repo

.bazelrc

And this to your .bazelrc

# .bazelrc

# Build using platforms by default
build --incompatible_enable_cc_toolchain_resolution
build --platforms=@arm_none_eabi//platforms:arm_none_generic

WORKSPACE

Add this git repository to your WORKSPACE to use the compiler

# WORKSPACE.bazel

load("@bazel_tools//tools/build_defs/repo:git.bzl", "git_repository")

git_repository(
    name = "arm_none_eabi",
    commit = "<commit>",
    remote = "https://github.com/hexdae/bazel-arm-none-eabi",
    shallow_since = "<value>",
)

load("@arm_none_eabi//:deps.bzl", "arm_none_eabi_deps", "register_default_arm_none_eabi_toolchains")

arm_none_eabi_deps()

register_default_arm_none_eabi_toolchains()

Bzlmod

Bazel mod support is experimental, add this to your module to use the compiler. Eventually this module will be released to BCR, but for now it requires a `git_override``

# MODULE.bazel

git_override(
    module_name = "arm_none_eabi",
    remote = "https://github.com/hexdae/bazel-arm-none-eabi",
    commit = "<commit>",
)

bazel_dep(name = "arm_none_eabi", version = "1.0.0")

arm_none_eabi_gcc = use_extension("@arm_none_eabi//:extensions.bzl", "arm_none_eabi")
arm_none_eabi_gcc.toolchain(version = "9.2.1")
use_repo(
    arm_none_eabi_gcc,
    "arm_none_eabi_darwin_x86_64",
    "arm_none_eabi_linux_aarch64",
    "arm_none_eabi_linux_x86_64",
    "arm_none_eabi_windows_x86_64",
)

register_toolchains("@arm_none_eabi//toolchain:all")

Now Bazel will automatically use arm-none-eabi-gcc as a compiler.

Custom toolchain

If you want to bake certain compiler flags in to your toolchain, you can define a custom arm-none-eabi toolchain in your repo.

In a BUILD file:

# path/to/toolchains/BUILD

load("@arm_none_eabi//toolchain:toolchain.bzl", "arm_none_eabi_toolchain")
arm_none_eabi_toolchain(
    name = "custom_toolchain",
    target_compatible_with = [
        "<your additional constraints>",
    ],
    copts = [
        "<your additional copts>",
    ],
    linkopts = [
        "<your additional linkopts>",
    ],
)

And in your WORKSPACE:

register_toolchains("@//path/to/toolchains:all")

Be careful about registering the default toolchains when using a custom one

Direct access to gcc tools

If you need direct access to gcc tools, they are available as @arm_none_eabi//:<tool>. For example, the following genrules could be used to produce .bin and .hex artifacts from a generic .out target.

cc_binary(
    name = "target.out"
    srcs = [...],
    deps = [...],
    copts = [...],
    ...
)

genrule(
    name = "bin",
    srcs = [":target.out"],
    outs = ["target.bin"],
    cmd = "$(execpath @arm_none_eabi//:objcopy) -O binary $< $@",
    tools = ["@arm_none_eabi//:objcopy"],
)

genrule(
    name = "hex",
    srcs = [":target.out"],
    outs = ["target.hex"],
    cmd = "$(execpath @arm_none_eabi//:objcopy) -O ihex $< $@",
    tools = ["@arm_none_eabi//:objcopy"],
)

Remote execution

This toolchain is compatible with remote execution, see remote.yml