bazel_bootlin

Provides hermetic Bazel C/C++ toolchains based on Buildroot toolchains provided by Bootlin.

Usage

WORKSPACE

To incorporate bazel_bootlin toolchains into your project, copy the following into your WORKSPACE file.

load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")

http_archive(
    name = "bazel_bootlin",
    # See release page for latest version url and sha.
)

load("@bazel_bootlin//:defs.bzl", "bootlin_toolchain")

bootlin_toolchain(
    name = "gcc_12_2",
    architecture = "x86-64",
    libc_impl = "glibc"
    buildroot_version = "bleeding-edge-2022.08-1",
)

register_toolchains(
    "@gcc_12_2//:toolchain",
)

• architecture - refers to the architecture string used by Bootlin.
• libc_impl - refers to the libc implementation (e.g. glibc, musl, or uclibc).
• buildroot_version - refers to the Buildroot version string (e.g. bleeding-edge-2022.08-1).

Available Toolchains

Currently bazel_bootlin only provides simplifyied registration for the toolchains listed in [toolchain/toolchain_info.bzl]. This list is easily expanded so feel free to add more as necessary. However it's possible to configure unsupported toolchains manually by passing extra parameters to the bootlin_toolchain rule, like in the example below:

bootlin_toolchain(
    name = "gcc_12_3",
    architecture = "x86-64",
    libc_impl = "glibc",
    buildroot_version = "stable-2023.08-1",
    sha256 = "d6eca7f1ea736ef6f868a027a9d0baa875f9513755026aed2badc04a2b9cd7bd",
    gcc_version ="12.3.0",
    libc_version = "glibc_2.35",
)

bootlin_toolchain(
    name = "riscv64_gcc",
    architecture = "riscv64-lp64d",
    libc_impl = "glibc",
    buildroot_version = "stable-2023.08-1",
    sha256 = "97d7f95ced5852e3fa0119fd5370356df0b652844a76ad9a1c88caa8dd09f367",
    gcc_version ="12.3.0",
    libc_version = "glibc_2.37",
)

• sha256 refers to the SHA256 hash of the toolchain archive.
• gcc_version refers to the GCC version string (e.g. 12.3.0).
• libc_version refers to the libc version string (e.g. glibc_2.35).

These values can be found on the Bootlin toolchains page.

Building With Bootlin Toolchains

In order to enable toolchain selection, Bazel requires flag --incompatible_enable_cc_toolchain_resolution.

Additionally, you may also want to use --action_env="BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN=1" to prevent accidental use of any local toolchains.

To avoid needing always specify these flags on the command line, you can add these to your .bazelrc file:

build --incompatible_enable_cc_toolchain_resolution
build --action_env="BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN=1"

Toolchain configuration

Toolchains can configured during definition:

# //:WORKSPACE.bazel

bootlin_toolchain(
    name = "gcc_12_2",
    architecture = "x86-64",
    libc_impl = "glibc"
    buildroot_version = "bleeding-edge-2022.08-1",
    extra_cxx_flags = [
        "-std=c++23",
        "-fdiagnostics-color=always",
        "-Wduplicated-cond",
        "-Wduplicated-branches",
        "-Wlogical-op",
        "-Wuseless-cast",
        "-Wshadow=compatible-local",
        "-Werror",
        "-Wall",
        "-Wextra",
        "-Wpedantic",
        "-Wconversion",
        "-Wnon-virtual-dtor",
        "-Wold-style-cast",
        "-Wcast-align",
        "-Wunused",
        "-Woverloaded-virtual",
        "-Wmisleading-indentation",
        "-Wnull-dereference",
        "-Wdouble-promotion",
        "-Wformat=2",
        "-Wimplicit-fallthrough",
    ],
)

Toolchain selection

If multiple toolchains are registered, toolchain resolution selects the first available and compatible toolchain. --extra_toolchains can then be used to select a specific toolchain when running Bazel:

# //:WORKSPACE.bazel

register_toolchains(
    "@gcc_12_2//:toolchain",
    "@gcc_11_5//:toolchain",
    "@clang_16_0//:...:"
)

bazel build --extra_toolchains="@gcc_12_2//:toolchain" //...

Toolchain features

bootlin_toolchain uses unix_cc_tooclahin_config and has same features.

For example:

bazel run <target> --features=asan