vsco / bazel-toolchains

A collection of Bazel C++ build infrastructure based on Chromium's LLVM toolchain.

Bazel Toolchains

A collection of Bazel C++ build infrastructure based on Chromium's LLVM toolchain. There are tags corresponding to Chromium releases. The build targets currently supported are Linux x64 and macOS. As in Chromium, the Linux toolchain has a sysroot, bundled copies of binutils, and a copy of libc++. The macOS build is less hermetic, and relies on system binutils and libraries.

Use it in your Bazel WORKSPACE file like this:

git_repository(
    name = 'co_vsco_bazel_toolchains',
    remote = 'https://github.com/vsco/bazel-toolchains',
    tag = 'v64.0.3282.167',
)

load("@co_vsco_bazel_toolchains//toolchains:repositories.bzl", "bazel_toolchains_repositories")
bazel_toolchains_repositories()

Invoke Bazel with the custom toolchain:

bazel build --crosstool_top=@co_vsco_bazel_toolchains//tools/cpp:default-toolchain //your/build:target

Bazel Compatibility

vsco/bazel-toolchains is tested against the following build matrix:

Bazel Version	OSX	Linux
0.20.0+	✗	✗
0.19.2	✓	✓
0.18.1	✓	✓
0.17.2	✓	✓
0.16.1	✓	✓
0.15.2	✓	✓
0.14.1	✓	✓
0.13.1	✓	✓
0.12.0	✓	✓
0.11.x	✗	✗
0.10.x	✗	✗
0.9.x	✗	✗

Builds beyond the listed versions are not currently tested.

Bazel 0.20.0+ introduced breaking changes to the C++ Toolchain API which need to be addressed for consumers of this repo in a non-breaking manner.

Prerequisites

On macOS, run xcode-select --install in Terminal.

Running the Python scripts

The files in the scripts/ directory are written in Python. Follow these instructions to install a version of Python that comes with the necessary tools for installation of third party libraries. On macOS, this means brew install python, and then following the instructions printed by brew info python (It's recommended to use python@2 for macOS).

Once that's working, type pip install requests to install the necessary dependencies.

From the root of this repository, type python scripts/generate_workspace.py --rev="64.0.3282.167" where --rev is the Chromium tag you wish to pull from. The script will print status messages to stderr and write a file similar to toolchains/repositories.bzl to stdout.

bazel-toolchains's Issues

Wrong tag with letter prefix "v61.0.3163.25"

The documentation says to use tag = "62.0.3178.0" while that tag is named v62.0.3178.0

Needs explicit deps on @org_chromium_libcxx

Hey there, thanks for the great work here.

I was wondering how to stop having to depend on '@org_chromium_libcxx//:cxx', and :cxxabi in each cc_library rule. It seems pretty tiresome to me. Custom macros are an option, but I was wondering if there was a way to add it to the CROSSTOOL configuration instead.

CROSTOOL question

Doesn't using system dir in the CROSSTOOL file make the build non-hermetic?

libunwind upstream doesn't exist

The repository rule points to a place (https://chromium.googlesource.com/chromium/llvm-project/libunwind) which doesn't exist.

Asan/Tsan/Msan

Is there a way to use Asan/Tsan/Msan with this toolchain? When I try (e.g. asan) I get an error:

chromium_ld: error: cannot open external/co_vsco_bazel_toolchains/tools/cpp/tool_wrappers/lib/clang/6.0.0/lib/linux/libclang_rt.asan-x86_64.a: No such file or directory

For some reason, chromium_ld is looking for libclang_rt.asan-x86_64.a under external/co_vsco_bazel_toolchains/tools/cpp/tool_wrappers instead of external/org_chromium_clang_linux_x64/...