cfrantz / crt_demo

Demo of Compiler Repository Toolkit

Compiler Repository Toolkit Demonstration

This repository demonstrates how to use the Compiler Repository Toolkit.

Configuration

• .bazelrc - In order to enable toolchain resolution, this file must contain the following line:

  build --incompatible_enable_cc_toolchain_resolution
  

• WORKSPACE.bazel - Your workspace file needs to load the crt repository and its dependencies. It must also register the toolchains you want to use.

  load("@crt//config:registration.bzl", "crt_register_toolchains")
  crt_register_toolchains(
      # Choose the toolchains you want:
      arm = True,
      win64 = True,
  )

• Building software is controlled by constraints. cc_library and cc_binaries can be restricted to certain platforms by use of the target_compatible_with attribute. In order to build software targeted at a particular platform, you can invoke bazel with the --platforms flag:

  bazel build //some:label --platforms=@crt//platforms/arm:cortex_m

• Platform targets can also be defined using a transition. Transitions cause bazel to evaluate the dependency graph as if a certain configuration were defined. For example, the target_platform rule evaluates the build graph as if --platforms were set to a particular value.

  For example, to build a target for cortex_m:

  target_platform(
      name = "rule-name",
      platform = "@crt//platforms/arm:cortex_m",
      target = "label to a binary artifact",
  )

• Targets can be executed under a emulation with the runner rule. The runner rule is also a transition rule: it declares the target platform and the execution configuration for that platform.

  For example:

  runner(
      name = "demo",
      binary = ":sieve",
      platform = "@crt//platforms/arm:cortex_m",
      exec_config = "@crt//platforms/arm:qemu",
  )