Provides hermetic Bazel C/C++ toolchains based on Buildroot toolchains provided by Bootlin.
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//toolchains:toolchains.bzl", "bootlin_all_toolchain_deps")
bootlin_all_toolchain_deps()
This will bring all of the available toolchains (and their associated
platform
definitions) into your project. The toolchains will
only be downloaded when actually utilized, but if you prefer, you can only import a specific
toolchain:
load("@bazel_bootlin//toolchains:toolchains.bzl", "bootlin_toolchain_deps")
bootlin_toolchain_deps(
architecture = "x86-64-core-i7",
cstdlib = "glibc",
buildroot_version = "2020.08-1",
)
architecture
- refers to the architecture string used by Bootlin.cstdlib
- refers to the cstdlib string used by bootlin.buildroot_version
- refers to the Buildroot version string used by Bootlin.
Currently bazel_bootlin
only provides the "glibc--stable" version of the following Bootlin
toolchains:
Architecture | cstdlib | Buildroot Version |
---|---|---|
x86-64 |
glibc |
2022.08-1 , 2021.11-5 |
x86-64-core-i7 |
glibc |
2020.08-1 |
aarch64 |
glibc , musl |
2021.11-1 , 2020.08-1 |
armv7-eabihf |
glibc |
2020.08-1 |
This list is easily expanded. If a toolchain of interest isn't available feel free to submit and
issue, or alternatively take a look at
_AVAILABLE_TOOLCHAINS
in setup_toolchains.py
and create a pull request.
Don't forget to actually run setup_toolchains.py
after adding a toolchain and before submitting a
PR:
bazel run //:setup_toolchains
bazel_bootlin
defines a different platform
for each
toolchain that is included. The platforms specify constraint_value
for the canonical
@platforms//os:os
and @platforms//cpu:cpu
constraint_setting
:
platform(
name = "{architecture}-linux-{cstdlib}-{buildroot_version}",
constraint_values = [
"@platforms//cpu:{architecture}",
"@platforms//os:linux",
"@bazel_bootlin//platforms:{buildroot_version}",
],
)
Specifying one of these platforms will cause Bazel to use the corresponding toolchain during build.
In order to enable toolchain selection via platforms, Bazel requires a special flag along with the target platform:
bazel build --incompatible_enable_cc_toolchain_resolution --platforms=@bazel_bootlin//platforms:{architecture}-linux-{cstdlib}-{buildroot_version} //...
The ergonomics can be improved by placing the flags in a
.bazelrc
file:
build --incompatible_enable_cc_toolchain_resolution
build --platforms=@bazel_bootlin//platforms:{architecture}-linux-{cstdlib}-{buildroot_version}
Then a simple bazel build //...
will utilize the desired toolchain.