crt_demo's Introduction

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",
)
```

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