Experiments with Bazel GCC compilation toolchains

This repository is some experimentation with using different gcc compiler toolchains.

Predefined Toolchains

This repository configures toolchains provided by https://toolchains.bootlin.com/ in bazel.

• All x86_64 toolchains bootlin provides are available. Run bazel query '//external:*' | grep gcc_toolchain for the full list.
• Additionally some convenience aliases are defined. See bazel query 'kind(toolchain, @gcc_toolchain//...)'.

Custom Toolchains

In case the bootlin toolchains are not sufficient you can build your own using https://crosstool-ng.github.io/. See util/ct-ng/README.md for some help on that.

load("//toolchain/crosstoolNG_gcc:defs.bzl", "crosstoolNG_toolchain")

crosstoolNG_toolchain(
    name = "gcc_toolchain",
    cxx_flags = ["-std=c++14"],
    sha256 = "...",
    url = "http://.../x86_64-unknown-linux-gnu.tar.bz2",
    variant = "x86_64-unknown-linux-gnu",
    version = "9.5.0",
)

Background Info

Chosen Toolchain

• https://toolchains.bootlin.com/
  • Provides a wide variation of GCC toolchains for different architectures. Includes various versions of GCC. But might limit the glibc compatiblitily to something new-ish.

Alternative GCC Distributions

• https://buildroot.org/ or https://crosstool-ng.github.io/
  • This requires to build the distribution and store the resulting artifacts somewhere. But it gives greater control over the used gcc/glibc/other tool versions.
  • Here crosstool-NG (and not buildroot) was chosen for the reasons outlined in https://crosstool-ng.github.io/docs/introduction/.
• https://github.com/xpack-dev-tools/gcc-xpack/

Related Bazel Toolchains

• https://github.com/bazel-contrib/toolchains_llvm
  • LLVM tooling instead of GCC.
• https://github.com/bazelembedded/bazel-embedded
  • Geared towards ARM embedded development.
• https://github.com/f0rmiga/gcc-toolchain
  • Includes support for Fortran. Currently limited to one version of GCC. Ships a separately build sysroot.
• https://github.com/hexdae/toolchains_arm_gnu/
  • Geared towards ARM embedded development.
• https://github.com/uber/hermetic_cc_toolchain
  • Using zig cc instead of GCC.