Bazel toolchain configurations for RBE

This directory contains Bazel toolchain configurations for RBE grouped by operating system.

It might be necessary to rebuild these configurations when the RBE toolchain container image for a specific operating system is updated, or when a new Bazel version is released.

Linux

Directories linux-bazel-<BAZEL VERSION> contain Bazel toolchain configurations for Linux RBE builds. Multiple such directories may exist to ease migrating from one Bazel version to the next.

Toolchain configuration regeneration instructions

The Linux RBE toolchain configuration must be regenerated whenever the Linux RBE toolchain container image changes, or when upgrading to a new Bazel version.

Step 1

Clone the bazel-toolchains repository, build the rbe_configs_gen binary, and put it in your $PATH:

$ git clone https://github.com/bazelbuild/bazel-toolchains

$ cd bazel-toolchains

# This assumes that $HOME/bin is in your $PATH.
$ go build -o $HOME/bin/rbe_configs_gen ./cmd/rbe_configs_gen/rbe_configs_gen.go

Step 2

Generate a new //bazel/toolchains/linux-bazel-<BAZEL VERSION> directory with the rbe_configs_gen CLI tool:

# Replace the <PLACEHOLDERS> as needed.
$ rbe_configs_gen \
      --bazel_version=<BAZEL VERSION> \
      --toolchain_container=gcr.io/skia-public/rbe-container-skcms-linux@sha256:<HASH OF MOST RECENT IMAGE> \
      --output_src_root=<PATH TO REPOSITORY CHECKOUT> \
      --output_config_path=bazel/toolchains/linux-bazel-<BAZEL VERSION> \
      --generate_java_configs=false \
      --exec_os=linux \
      --target_os=linux

If rbe_configs_gen fails, try deleting all files under //bazel/toolchains/linux-bazel-<BAZEL VERSION> (if it exists) and re-run rbe_configs_gen.

Step 3

Add an empty //bazel/toolchains/linux-bazel-<BAZEL VERSION>/WORKSPACE file.

Step 4

Open file //bazel/toolchains/linux-bazel-<BAZEL VERSION>/config/BUILD, look for the toolchain rule named cc-toolchain, and replace the toolchain attribute as follows:

# Before.
toolchain(
    name = "cc-toolchain",
    ...
    toolchain = "//bazel/toolchains/linux-bazel-4.2.1/cc:cc-compiler-k8",
    ...
)

# After.
toolchain(
    name = "cc-toolchain",
    ...
    toolchain = "//cc:cc-compiler-k8",
    ...
)

Next, look for the platform rule named platform, and make the following change:

# Before.
platform(
    name = "platform",
    ...
    exec_properties = {
        ...
    },
    ...
)

# After.
platform(
    name = "platform",
    ...
    exec_properties = {
        ...
        "dockerAddCapabilities": "SYS_PTRACE",
    },
    ...
)

This is necessary to run tests on Linux RBE with --config=asan (details here).

(As an alternative, we could disable memory leak detection by setting the environment variable ASAN_OPTIONS=detect_leaks=1 via the --action_env Bazel flag.)

Step 5

Update the paths in //WORKSPACE as needed.

Windows

TODO(lovisolo)

macOS

TODO(lovisolo)