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| <h1 id="fuchsia-integration-tests"><a class="header" href="#fuchsia-integration-tests">Fuchsia integration tests</a></h1> |
| <p><a href="https://fuchsia.dev">Fuchsia</a> is an open-source operating system with about 2 |
| million lines of Rust code.<sup class="footnote-reference" id="fr-loc-1"><a href="#footnote-loc">1</a></sup> It has caught a large number of <a href="https://gist.github.com/tmandry/7103eba4bd6a6fb0c439b5a90ae355fa">regressions</a> |
| in the past and was subsequently included in CI.</p> |
| <h2 id="what-to-do-if-the-fuchsia-job-breaks"><a class="header" href="#what-to-do-if-the-fuchsia-job-breaks">What to do if the Fuchsia job breaks?</a></h2> |
| <p>Please contact the <a href="../../notification-groups/fuchsia.html">fuchsia</a> ping group and ask them for help.</p> |
| <pre><code class="language-text">@rustbot ping fuchsia |
| </code></pre> |
| <h2 id="building-fuchsia-in-ci"><a class="header" href="#building-fuchsia-in-ci">Building Fuchsia in CI</a></h2> |
| <p>Fuchsia builds as part of the suite of bors tests that run before a pull request |
| is merged.</p> |
| <p>If you are worried that a pull request might break the Fuchsia builder and want |
| to test it out before submitting it to the bors queue, simply ask bors to run |
| the try job that builds the Fuchsia integration: <code>@bors try jobs=x86_64-fuchsia</code>.</p> |
| <h2 id="building-fuchsia-locally"><a class="header" href="#building-fuchsia-locally">Building Fuchsia locally</a></h2> |
| <p>Because Fuchsia uses languages other than Rust, it does not use Cargo as a build |
| system. It also requires the toolchain build to be configured in a <a href="https://fuchsia.dev/fuchsia-src/development/build/rust_toolchain">certain |
| way</a>.</p> |
| <p>The recommended way to build Fuchsia is to use the Docker scripts that check out |
| and run a Fuchsia build for you. If you've run Docker tests before, you can |
| simply run this command from your Rust checkout to download and build Fuchsia |
| using your local Rust toolchain.</p> |
| <pre><code>src/ci/docker/run.sh x86_64-fuchsia |
| </code></pre> |
| <p>See the <a href="../docker.html">Testing with Docker</a> chapter for more details on how to run |
| and debug jobs with Docker.</p> |
| <p>Note that a Fuchsia checkout is <em>large</em> – as of this writing, a checkout and |
| build takes 46G of space – and as you might imagine, it takes a while to |
| complete.</p> |
| <h3 id="modifying-the-fuchsia-checkout"><a class="header" href="#modifying-the-fuchsia-checkout">Modifying the Fuchsia checkout</a></h3> |
| <p>The main reason you would want to build Fuchsia locally is because you need to |
| investigate a regression. After running a Docker build, you'll find the Fuchsia |
| checkout inside the <code>obj/fuchsia</code> directory of your Rust checkout. If you |
| modify the <code>KEEP_CHECKOUT</code> line in the <a href="https://github.com/rust-lang/rust/blob/221e2741c39515a5de6da42d8c76ee1e132c2c74/src/ci/docker/host-x86_64/x86_64-fuchsia/build-fuchsia.sh">build-fuchsia.sh</a> script to |
| <code>KEEP_CHECKOUT=1</code>, you can change the checkout as needed and rerun the build |
| command above. This will reuse all the build results from before.</p> |
| <p>You can find more options to customize the Fuchsia checkout in the |
| <a href="https://github.com/rust-lang/rust/blob/221e2741c39515a5de6da42d8c76ee1e132c2c74/src/ci/docker/host-x86_64/x86_64-fuchsia/build-fuchsia.sh">build-fuchsia.sh</a> script.</p> |
| <h3 id="customizing-the-fuchsia-build"><a class="header" href="#customizing-the-fuchsia-build">Customizing the Fuchsia build</a></h3> |
| <p>You can find more info about the options used to build Fuchsia in Rust CI in the |
| <a href="https://cs.opensource.google/fuchsia/fuchsia/+/main:scripts/rust/build_fuchsia_from_rust_ci.sh?q=build_fuchsia_from_rust_ci&ss=fuchsia">build_fuchsia_from_rust_ci.sh</a> script invoked by <a href="https://github.com/rust-lang/rust/blob/221e2741c39515a5de6da42d8c76ee1e132c2c74/src/ci/docker/host-x86_64/x86_64-fuchsia/build-fuchsia.sh">build-fuchsia.sh</a>.</p> |
| <p>The Fuchsia build system uses <a href="https://gn.googlesource.com/gn/+/main#gn">GN</a>, a metabuild system that generates <a href="https://ninja-build.org/">Ninja</a> |
| files and then hands off the work of running the build to Ninja.</p> |
| <p>Fuchsia developers use <code>fx</code> to run builds and perform other development tasks. |
| This tool is located in <code>.jiri_root/bin</code> of the Fuchsia checkout; you may need |
| to add this to your <code>$PATH</code> for some workflows.</p> |
| <p>There are a few <code>fx</code> subcommands that are relevant, including:</p> |
| <ul> |
| <li><code>fx set</code> accepts build arguments, writes them to <code>out/default/args.gn</code>, and |
| runs GN.</li> |
| <li><code>fx build</code> builds the Fuchsia project using Ninja. It will automatically pick |
| up changes to build arguments and rerun GN. By default it builds everything, |
| but it also accepts target paths to build specific targets (see below).</li> |
| <li><code>fx clippy</code> runs Clippy on specific Rust targets (or all of them). We use this |
| in the Rust CI build to avoid running codegen on most Rust targets. Underneath |
| it invokes Ninja, just like <code>fx build</code>. The clippy results are saved in json |
| files inside the build output directory before being printed.</li> |
| </ul> |
| <h4 id="target-paths"><a class="header" href="#target-paths">Target paths</a></h4> |
| <p>GN uses paths like the following to identify build targets:</p> |
| <pre><code>//src/starnix/kernel:starnix_core |
| </code></pre> |
| <p>The initial <code>//</code> means the root of the checkout, and the remaining slashes are |
| directory names. The string after <code>:</code> is the <em>target name</em> of a target defined |
| in the <code>BUILD.gn</code> file of that directory.</p> |
| <p>The target name can be omitted if it is the same as the directory name. In other |
| words, <code>//src/starnix/kernel</code> is the same as <code>//src/starnix/kernel:kernel</code>.</p> |
| <p>These target paths are used inside <code>BUILD.gn</code> files to reference dependencies, |
| and can also be used in <code>fx build</code>.</p> |
| <h4 id="modifying-compiler-flags"><a class="header" href="#modifying-compiler-flags">Modifying compiler flags</a></h4> |
| <p>You can put custom compiler flags inside a GN <code>config</code> that is added to a |
| target. As a simple example:</p> |
| <pre><code>config("everybody_loops") { |
| rustflags = [ "-Zeverybody-loops" ] |
| } |
| |
| rustc_binary("example") { |
| crate_root = "src/bin.rs" |
| # ...existing keys here... |
| configs += [ ":everybody_loops" ] |
| } |
| </code></pre> |
| <p>This will add the flag <code>-Zeverybody-loops</code> to rustc when building the <code>example</code> |
| target. Note that you can also use <a href="https://gn.googlesource.com/gn/+/main/docs/reference.md#var_public_configs"><code>public_configs</code></a> for a config to be added |
| to every target that depends on that target.</p> |
| <p>If you want to add a flag to every Rust target in the build, you can add |
| rustflags to the <a href="https://cs.opensource.google/fuchsia/fuchsia/+/main:build/config/BUILD.gn;l=121;drc=c26c473bef93b33117ae417893118907a026fec7"><code>//build/config:compiler</code></a> config or to the OS-specific |
| configs referenced in that file. Note that <code>cflags</code> and <code>ldflags</code> are ignored on |
| Rust targets.</p> |
| <h4 id="running-ninja-and-rustc-commands-directly"><a class="header" href="#running-ninja-and-rustc-commands-directly">Running ninja and rustc commands directly</a></h4> |
| <p>Going down one layer, <code>fx build</code> invokes <code>ninja</code>, which in turn eventually |
| invokes <code>rustc</code>. All build actions are run inside the out directory, which is |
| usually <code>out/default</code> inside the Fuchsia checkout.</p> |
| <p>You can get ninja to print the actual command it invokes by forcing that command |
| to fail, e.g. by adding a syntax error to one of the source files of the target. |
| Once you have the command, you can run it from inside the output directory.</p> |
| <p>After changing the toolchain itself, the build setting <code>rustc_version_string</code> in |
| <code>out/default/args.gn</code> needs to be changed so that <code>fx build</code> or <code>ninja</code> will |
| rebuild all the Rust targets. This can be done in a text editor and the contents |
| of the string do not matter, as long as it changes from one build to the next. |
| <a href="https://cs.opensource.google/fuchsia/fuchsia/+/main:scripts/rust/build_fuchsia_from_rust_ci.sh?q=build_fuchsia_from_rust_ci&ss=fuchsia">build_fuchsia_from_rust_ci.sh</a> does this for you by hashing the toolchain |
| directory.</p> |
| <p>The Fuchsia website has more detailed documentation of the <a href="https://fuchsia.dev/fuchsia-src/development/build/build_system">build system</a>.</p> |
| <h4 id="other-tips-and-tricks"><a class="header" href="#other-tips-and-tricks">Other tips and tricks</a></h4> |
| <p>When using <code>build_fuchsia_from_rust_ci.sh</code> you can comment out the <code>fx set</code> |
| command after the initial run so it won't rerun GN each time. If you do this you |
| can also comment out the version_string line to save a couple seconds.</p> |
| <p><code>export NINJA_PERSISTENT_MODE=1</code> to get faster ninja startup times after the |
| initial build.</p> |
| <h2 id="fuchsia-target-support"><a class="header" href="#fuchsia-target-support">Fuchsia target support</a></h2> |
| <p>To learn more about Fuchsia target support, see the Fuchsia chapter in <a href="https://doc.rust-lang.org/nightly/rustc/platform-support/fuchsia.html">the |
| rustc book</a>.</p> |
| <hr> |
| <ol class="footnote-definition"><li id="footnote-loc"> |
| <p>As of June 2024, Fuchsia had about 2 million lines of first-party Rust |
| code and a roughly equal amount of third-party code, as counted by tokei |
| (excluding comments and blanks). <a href="#fr-loc-1">↩</a></p> |
| </li> |
| </ol> |
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