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| <ol class="chapter"><li class="chapter-item affix "><a href="about-this-guide.html">About this guide</a></li><li class="chapter-item affix "><a href="getting-started.html" class="active">Getting Started</a></li><li class="spacer"></li><li class="chapter-item affix "><li class="part-title">Building and debugging rustc</li><li class="chapter-item "><a href="building/how-to-build-and-run.html"><strong aria-hidden="true">1.</strong> How to Build and Run the Compiler</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="building/prerequisites.html"><strong aria-hidden="true">1.1.</strong> Prerequisites</a></li><li class="chapter-item "><a href="building/suggested.html"><strong aria-hidden="true">1.2.</strong> Suggested Workflows</a></li><li class="chapter-item "><a href="building/build-install-distribution-artifacts.html"><strong aria-hidden="true">1.3.</strong> Distribution artifacts</a></li><li class="chapter-item "><a href="building/compiler-documenting.html"><strong aria-hidden="true">1.4.</strong> Documenting Compiler</a></li><li class="chapter-item "><a href="rustdoc.html"><strong aria-hidden="true">1.5.</strong> Rustdoc overview</a></li><li class="chapter-item "><a href="building/new-target.html"><strong aria-hidden="true">1.6.</strong> Adding a new target</a></li></ol></li><li class="chapter-item "><a href="tests/intro.html"><strong aria-hidden="true">2.</strong> The compiler testing framework</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="tests/running.html"><strong aria-hidden="true">2.1.</strong> Running tests</a></li><li class="chapter-item "><a href="tests/adding.html"><strong aria-hidden="true">2.2.</strong> Adding new tests</a></li><li class="chapter-item "><a href="compiletest.html"><strong aria-hidden="true">2.3.</strong> Using compiletest commands to control test execution</a></li></ol></li><li class="chapter-item "><a href="compiler-debugging.html"><strong aria-hidden="true">3.</strong> Debugging the Compiler</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="tracing.html"><strong aria-hidden="true">3.1.</strong> Using the tracing/logging instrumentation</a></li></ol></li><li class="chapter-item "><a href="profiling.html"><strong aria-hidden="true">4.</strong> Profiling the compiler</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="profiling/with_perf.html"><strong aria-hidden="true">4.1.</strong> with the linux perf tool</a></li><li class="chapter-item "><a href="profiling/wpa_profiling.html"><strong aria-hidden="true">4.2.</strong> with Windows Performance Analyzer</a></li></ol></li><li class="chapter-item "><a href="crates-io.html"><strong aria-hidden="true">5.</strong> crates.io Dependencies</a></li><li class="chapter-item affix "><li class="part-title">Contributing to Rust</li><li class="chapter-item "><a href="contributing.html"><strong aria-hidden="true">6.</strong> Introduction</a></li><li class="chapter-item "><a href="compiler-team.html"><strong aria-hidden="true">7.</strong> About the compiler team</a></li><li class="chapter-item "><a href="git.html"><strong aria-hidden="true">8.</strong> Using Git</a></li><li class="chapter-item "><a href="rustbot.html"><strong aria-hidden="true">9.</strong> Mastering @rustbot</a></li><li class="chapter-item "><a href="walkthrough.html"><strong aria-hidden="true">10.</strong> Walkthrough: a typical contribution</a></li><li class="chapter-item "><a href="bug-fix-procedure.html"><strong aria-hidden="true">11.</strong> Bug Fix Procedure</a></li><li class="chapter-item "><a href="implementing_new_features.html"><strong aria-hidden="true">12.</strong> Implementing new features</a></li><li class="chapter-item "><a href="stability.html"><strong aria-hidden="true">13.</strong> Stability attributes</a></li><li class="chapter-item "><a href="stabilization_guide.html"><strong aria-hidden="true">14.</strong> Stabilizing Features</a></li><li class="chapter-item "><a href="feature-gates.html"><strong aria-hidden="true">15.</strong> Feature Gates</a></li><li class="chapter-item "><a href="conventions.html"><strong aria-hidden="true">16.</strong> Coding conventions</a></li><li class="chapter-item "><a href="notification-groups/about.html"><strong aria-hidden="true">17.</strong> Notification groups</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="notification-groups/arm.html"><strong aria-hidden="true">17.1.</strong> ARM</a></li><li class="chapter-item "><a href="notification-groups/cleanup-crew.html"><strong aria-hidden="true">17.2.</strong> Cleanup Crew</a></li><li class="chapter-item "><a href="notification-groups/llvm.html"><strong aria-hidden="true">17.3.</strong> LLVM</a></li><li class="chapter-item "><a href="notification-groups/risc-v.html"><strong aria-hidden="true">17.4.</strong> RISC-V</a></li><li class="chapter-item "><a href="notification-groups/windows.html"><strong aria-hidden="true">17.5.</strong> Windows</a></li></ol></li><li class="chapter-item "><a href="licenses.html"><strong aria-hidden="true">18.</strong> Licenses</a></li><li class="chapter-item affix "><li class="part-title">High-level Compiler Architecture</li><li class="chapter-item "><a href="part-2-intro.html"><strong aria-hidden="true">19.</strong> Prologue</a></li><li class="chapter-item "><a href="overview.html"><strong aria-hidden="true">20.</strong> Overview of the Compiler</a></li><li class="chapter-item "><a href="compiler-src.html"><strong aria-hidden="true">21.</strong> The compiler source code</a></li><li class="chapter-item "><a href="building/bootstrapping.html"><strong aria-hidden="true">22.</strong> Bootstrapping</a></li><li class="chapter-item "><a href="query.html"><strong aria-hidden="true">23.</strong> Queries: demand-driven compilation</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="queries/query-evaluation-model-in-detail.html"><strong aria-hidden="true">23.1.</strong> The Query Evaluation Model in Detail</a></li><li class="chapter-item "><a href="queries/incremental-compilation.html"><strong aria-hidden="true">23.2.</strong> Incremental compilation</a></li><li class="chapter-item "><a href="queries/incremental-compilation-in-detail.html"><strong aria-hidden="true">23.3.</strong> Incremental compilation In Detail</a></li><li class="chapter-item "><a href="incrcomp-debugging.html"><strong aria-hidden="true">23.4.</strong> Debugging and Testing</a></li><li class="chapter-item "><a href="salsa.html"><strong aria-hidden="true">23.5.</strong> Salsa</a></li></ol></li><li class="chapter-item "><a href="memory.html"><strong aria-hidden="true">24.</strong> Memory Management in Rustc</a></li><li class="chapter-item "><a href="serialization.html"><strong aria-hidden="true">25.</strong> Serialization in Rustc</a></li><li class="chapter-item "><a href="parallel-rustc.html"><strong aria-hidden="true">26.</strong> Parallel Compilation</a></li><li class="chapter-item "><a href="rustdoc-internals.html"><strong aria-hidden="true">27.</strong> Rustdoc internals</a></li><li class="chapter-item affix "><li class="part-title">Source Code Representation</li><li class="chapter-item "><a href="part-3-intro.html"><strong aria-hidden="true">28.</strong> Prologue</a></li><li class="chapter-item "><a href="cli.html"><strong aria-hidden="true">29.</strong> Command-line arguments</a></li><li class="chapter-item "><a href="rustc-driver.html"><strong aria-hidden="true">30.</strong> The Rustc Driver and Interface</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="rustc-driver-interacting-with-the-ast.html"><strong aria-hidden="true">30.1.</strong> Ex: Type checking through rustc_interface</a></li><li class="chapter-item "><a href="rustc-driver-getting-diagnostics.html"><strong aria-hidden="true">30.2.</strong> Ex: Getting diagnostics through rustc_interface</a></li></ol></li><li class="chapter-item "><a href="syntax-intro.html"><strong aria-hidden="true">31.</strong> Syntax and the AST</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="the-parser.html"><strong aria-hidden="true">31.1.</strong> Lexing and Parsing</a></li><li class="chapter-item "><a href="macro-expansion.html"><strong aria-hidden="true">31.2.</strong> Macro expansion</a></li><li class="chapter-item "><a href="name-resolution.html"><strong aria-hidden="true">31.3.</strong> Name resolution</a></li><li class="chapter-item "><a href="test-implementation.html"><strong aria-hidden="true">31.4.</strong> #[test] Implementation</a></li><li class="chapter-item "><a href="panic-implementation.html"><strong aria-hidden="true">31.5.</strong> Panic Implementation</a></li><li class="chapter-item "><a href="ast-validation.html"><strong aria-hidden="true">31.6.</strong> AST Validation</a></li><li class="chapter-item "><a href="feature-gate-ck.html"><strong aria-hidden="true">31.7.</strong> Feature Gate Checking</a></li><li class="chapter-item "><a href="lang-items.html"><strong aria-hidden="true">31.8.</strong> Lang Items</a></li></ol></li><li class="chapter-item "><a href="hir.html"><strong aria-hidden="true">32.</strong> The HIR (High-level IR)</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="lowering.html"><strong aria-hidden="true">32.1.</strong> Lowering AST to HIR</a></li><li class="chapter-item "><a href="hir-debugging.html"><strong aria-hidden="true">32.2.</strong> Debugging</a></li></ol></li><li class="chapter-item "><a href="thir.html"><strong aria-hidden="true">33.</strong> The THIR (Typed High-level IR)</a></li><li class="chapter-item "><a href="mir/index.html"><strong aria-hidden="true">34.</strong> The MIR (Mid-level IR)</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="mir/construction.html"><strong aria-hidden="true">34.1.</strong> MIR construction</a></li><li class="chapter-item "><a href="mir/visitor.html"><strong aria-hidden="true">34.2.</strong> MIR visitor and traversal</a></li><li class="chapter-item "><a href="mir/passes.html"><strong aria-hidden="true">34.3.</strong> MIR passes: getting the MIR for a function</a></li></ol></li><li class="chapter-item "><a href="identifiers.html"><strong aria-hidden="true">35.</strong> Identifiers in the Compiler</a></li><li class="chapter-item "><a href="closure.html"><strong aria-hidden="true">36.</strong> Closure expansion</a></li><li class="chapter-item affix "><li class="part-title">Analysis</li><li class="chapter-item "><a href="part-4-intro.html"><strong aria-hidden="true">37.</strong> Prologue</a></li><li class="chapter-item "><a href="ty.html"><strong aria-hidden="true">38.</strong> The ty module: representing types</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="generics.html"><strong aria-hidden="true">38.1.</strong> Generics and substitutions</a></li><li class="chapter-item "><a href="ty-fold.html"><strong aria-hidden="true">38.2.</strong> TypeFolder and TypeFoldable</a></li><li class="chapter-item "><a href="generic_arguments.html"><strong aria-hidden="true">38.3.</strong> Generic arguments</a></li><li class="chapter-item "><a href="constants.html"><strong aria-hidden="true">38.4.</strong> Constants in the type system</a></li></ol></li><li class="chapter-item "><a href="type-inference.html"><strong aria-hidden="true">39.</strong> Type inference</a></li><li class="chapter-item "><a href="traits/resolution.html"><strong aria-hidden="true">40.</strong> Trait solving</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="early-late-bound.html"><strong aria-hidden="true">40.1.</strong> Early and Late Bound Parameters</a></li><li class="chapter-item "><a href="traits/hrtb.html"><strong aria-hidden="true">40.2.</strong> Higher-ranked trait bounds</a></li><li class="chapter-item "><a href="traits/caching.html"><strong aria-hidden="true">40.3.</strong> Caching subtleties</a></li><li class="chapter-item "><a href="traits/specialization.html"><strong aria-hidden="true">40.4.</strong> Specialization</a></li><li class="chapter-item "><a href="traits/chalk.html"><strong aria-hidden="true">40.5.</strong> Chalk-based trait solving</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="traits/lowering-to-logic.html"><strong aria-hidden="true">40.5.1.</strong> Lowering to logic</a></li><li class="chapter-item "><a href="traits/goals-and-clauses.html"><strong aria-hidden="true">40.5.2.</strong> Goals and clauses</a></li><li class="chapter-item "><a href="traits/canonical-queries.html"><strong aria-hidden="true">40.5.3.</strong> Canonical queries</a></li></ol></li></ol></li><li class="chapter-item "><a href="type-checking.html"><strong aria-hidden="true">41.</strong> Type checking</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="method-lookup.html"><strong aria-hidden="true">41.1.</strong> Method Lookup</a></li><li class="chapter-item "><a href="variance.html"><strong aria-hidden="true">41.2.</strong> Variance</a></li><li class="chapter-item "><a href="opaque-types-type-alias-impl-trait.html"><strong aria-hidden="true">41.3.</strong> Opaque Types</a></li></ol></li><li class="chapter-item "><a href="pat-exhaustive-checking.html"><strong aria-hidden="true">42.</strong> Pattern and Exhaustiveness Checking</a></li><li class="chapter-item "><a href="mir/dataflow.html"><strong aria-hidden="true">43.</strong> MIR dataflow</a></li><li class="chapter-item "><a href="borrow_check.html"><strong aria-hidden="true">44.</strong> The borrow checker</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="borrow_check/moves_and_initialization.html"><strong aria-hidden="true">44.1.</strong> Tracking moves and initialization</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="borrow_check/moves_and_initialization/move_paths.html"><strong aria-hidden="true">44.1.1.</strong> Move paths</a></li></ol></li><li class="chapter-item "><a href="borrow_check/type_check.html"><strong aria-hidden="true">44.2.</strong> MIR type checker</a></li><li class="chapter-item "><a href="borrow_check/region_inference.html"><strong aria-hidden="true">44.3.</strong> Region inference</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="borrow_check/region_inference/constraint_propagation.html"><strong aria-hidden="true">44.3.1.</strong> Constraint propagation</a></li><li class="chapter-item "><a href="borrow_check/region_inference/lifetime_parameters.html"><strong aria-hidden="true">44.3.2.</strong> Lifetime parameters</a></li><li class="chapter-item "><a href="borrow_check/region_inference/member_constraints.html"><strong aria-hidden="true">44.3.3.</strong> Member constraints</a></li><li class="chapter-item "><a href="borrow_check/region_inference/placeholders_and_universes.html"><strong aria-hidden="true">44.3.4.</strong> Placeholders and universes</a></li><li class="chapter-item "><a href="borrow_check/region_inference/closure_constraints.html"><strong aria-hidden="true">44.3.5.</strong> Closure constraints</a></li><li class="chapter-item "><a href="borrow_check/region_inference/error_reporting.html"><strong aria-hidden="true">44.3.6.</strong> Error reporting</a></li></ol></li><li class="chapter-item "><a href="borrow_check/two_phase_borrows.html"><strong aria-hidden="true">44.4.</strong> Two-phase-borrows</a></li></ol></li><li class="chapter-item "><a href="param_env.html"><strong aria-hidden="true">45.</strong> Parameter Environments</a></li><li class="chapter-item "><a href="diagnostics.html"><strong aria-hidden="true">46.</strong> Errors and Lints</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="diagnostics/sessiondiagnostic.html"><strong aria-hidden="true">46.1.</strong> Creating Errors With SessionDiagnostic</a></li><li class="chapter-item "><a href="diagnostics/lintstore.html"><strong aria-hidden="true">46.2.</strong> LintStore</a></li><li class="chapter-item "><a href="diagnostics/diagnostic-codes.html"><strong aria-hidden="true">46.3.</strong> Diagnostic Codes</a></li><li class="chapter-item "><a href="diagnostics/diagnostic-items.html"><strong aria-hidden="true">46.4.</strong> Diagnostic Items</a></li></ol></li><li class="chapter-item "><li class="part-title">MIR to Binaries</li><li class="chapter-item "><a href="part-5-intro.html"><strong aria-hidden="true">47.</strong> Prologue</a></li><li class="chapter-item "><a href="mir/optimizations.html"><strong aria-hidden="true">48.</strong> MIR optimizations</a></li><li class="chapter-item "><a href="mir/debugging.html"><strong aria-hidden="true">49.</strong> Debugging</a></li><li class="chapter-item "><a href="const-eval.html"><strong aria-hidden="true">50.</strong> Constant evaluation</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="miri.html"><strong aria-hidden="true">50.1.</strong> miri const evaluator</a></li></ol></li><li class="chapter-item "><a href="backend/monomorph.html"><strong aria-hidden="true">51.</strong> Monomorphization</a></li><li class="chapter-item "><a href="backend/lowering-mir.html"><strong aria-hidden="true">52.</strong> Lowering MIR</a></li><li class="chapter-item "><a href="backend/codegen.html"><strong aria-hidden="true">53.</strong> Code Generation</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="backend/updating-llvm.html"><strong aria-hidden="true">53.1.</strong> Updating LLVM</a></li><li class="chapter-item "><a href="backend/debugging.html"><strong aria-hidden="true">53.2.</strong> Debugging LLVM</a></li><li class="chapter-item "><a href="backend/backend-agnostic.html"><strong aria-hidden="true">53.3.</strong> Backend Agnostic Codegen</a></li><li class="chapter-item "><a href="backend/implicit-caller-location.html"><strong aria-hidden="true">53.4.</strong> Implicit Caller Location</a></li></ol></li><li class="chapter-item "><a href="backend/libs-and-metadata.html"><strong aria-hidden="true">54.</strong> Libraries and Metadata</a></li><li class="chapter-item "><a href="profile-guided-optimization.html"><strong aria-hidden="true">55.</strong> Profile-guided Optimization</a></li><li class="chapter-item "><a href="llvm-coverage-instrumentation.html"><strong aria-hidden="true">56.</strong> LLVM Source-Based Code Coverage</a></li><li class="chapter-item "><a href="sanitizers.html"><strong aria-hidden="true">57.</strong> Sanitizers Support</a></li><li class="chapter-item "><a href="debugging-support-in-rustc.html"><strong aria-hidden="true">58.</strong> Debugging Support in the Rust Compiler</a></li><li class="spacer"></li><li class="chapter-item affix "><a href="appendix/background.html">Appendix A: Background topics</a></li><li class="chapter-item affix "><a href="appendix/glossary.html">Appendix B: Glossary</a></li><li class="chapter-item affix "><a href="appendix/code-index.html">Appendix C: Code Index</a></li><li class="chapter-item affix "><a href="appendix/compiler-lecture.html">Appendix D: Compiler Lecture Series</a></li><li class="chapter-item affix "><a href="appendix/bibliography.html">Appendix E: Bibliography</a></li><li class="chapter-item affix "><a href="appendix/humorust.html">Appendix Z: HumorRust</a></li><li 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| <main> |
| <h1 id="getting-started"><a class="header" href="#getting-started">Getting Started</a></h1> |
| <ul> |
| <li><a href="#asking-questions">Asking Questions</a> |
| <ul> |
| <li><a href="#experts">Experts</a></li> |
| <li><a href="#etiquette">Etiquette</a></li> |
| </ul> |
| </li> |
| <li><a href="#cloning-and-building">Cloning and Building</a> |
| <ul> |
| <li><a href="#system-requirements">System Requirements</a></li> |
| <li><a href="#cloning">Cloning</a></li> |
| <li><a href="#configuring-the-compiler">Configuring the Compiler</a></li> |
| <li><a href="#xpy-intro">x.py Intro</a></li> |
| <li><a href="#building-and-testing-rustc">Building and Testing <code>rustc</code></a></li> |
| <li><a href="#building-and-testing-stdcorealloctestproc_macroetc">Building and Testing <code>std</code>/<code>core</code>/<code>alloc</code>/<code>test</code>/<code>proc_macro</code>/etc.</a></li> |
| <li><a href="#building-and-testing-rustdoc">Building and Testing <code>rustdoc</code></a></li> |
| <li><a href="#contributing-code-to-other-rust-projects">Contributing code to other Rust projects</a></li> |
| <li><a href="#other-ways-to-contribute">Other ways to contribute</a></li> |
| </ul> |
| </li> |
| <li><a href="#contributor-procedures">Contributor Procedures</a> |
| <ul> |
| <li><a href="#code-review">Code Review</a></li> |
| <li><a href="#bug-fixes-or-normal-code-changes">Bug Fixes or "Normal" code changes</a></li> |
| <li><a href="#new-features">New Features</a></li> |
| <li><a href="#breaking-changes">Breaking Changes</a></li> |
| <li><a href="#major-changes">Major Changes</a></li> |
| <li><a href="#performance">Performance</a></li> |
| </ul> |
| </li> |
| <li><a href="#other-resources">Other Resources</a></li> |
| </ul> |
| <p>This documentation is <em>not</em> intended to be comprehensive; it is meant to be a |
| quick guide for the most useful things. For more information, <a href="./building/how-to-build-and-run.html">see this |
| chapter on how to build and run the compiler</a>.</p> |
| <h2 id="asking-questions"><a class="header" href="#asking-questions">Asking Questions</a></h2> |
| <p>The compiler team (or <code>t-compiler</code>) usually hangs out in Zulip <a href="https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler">in this |
| "stream"</a>; it will be easiest to get questions answered there.</p> |
| <p><strong>Please ask questions!</strong> A lot of people report feeling that they are "wasting |
| expert time", but nobody on <code>t-compiler</code> feels this way. Contributors are |
| important to us.</p> |
| <p>Also, if you feel comfortable, prefer public topics, as this means others can |
| see the questions and answers, and perhaps even integrate them back into this |
| guide :)</p> |
| <h3 id="experts"><a class="header" href="#experts">Experts</a></h3> |
| <p>Not all <code>t-compiler</code> members are experts on all parts of <code>rustc</code>; it's a pretty |
| large project. To find out who has expertise on different parts of the |
| compiler, <a href="https://github.com/rust-lang/compiler-team/blob/master/content/experts/map.toml">consult this "experts map"</a>.</p> |
| <p>It's not perfectly complete, though, so please also feel free to ask questions |
| even if you can't figure out who to ping.</p> |
| <h3 id="etiquette"><a class="header" href="#etiquette">Etiquette</a></h3> |
| <p>We do ask that you be mindful to include as much useful information as you can |
| in your question, but we recognize this can be hard if you are unfamiliar with |
| contributing to Rust.</p> |
| <p>Just pinging someone without providing any context can be a bit annoying and |
| just create noise, so we ask that you be mindful of the fact that the |
| <code>t-compiler</code> folks get a lot of pings in a day.</p> |
| <h2 id="cloning-and-building"><a class="header" href="#cloning-and-building">Cloning and Building</a></h2> |
| <p>The main repository is <a href="https://github.com/rust-lang/rust"><code>rust-lang/rust</code></a>. This contains the compiler, |
| the standard library (including <code>core</code>, <code>alloc</code>, <code>test</code>, <code>proc_macro</code>, etc), |
| and a bunch of tools (e.g. <code>rustdoc</code>, the bootstrapping infrastructure, etc).</p> |
| <p>There are also a bunch of submodules for things like LLVM, <code>clippy</code>, <code>miri</code>, |
| etc. You don't need to clone these immediately, but the build tool will |
| automatically clone and sync them (more on this later).</p> |
| <p><a href="./building/suggested.html"><strong>Take a look at the "Suggested Workflows" chapter for some helpful |
| advice.</strong></a></p> |
| <h3 id="system-requirements"><a class="header" href="#system-requirements">System Requirements</a></h3> |
| <p><a href="./building/prerequisites.html"><strong>See this chapter for detailed software requirements.</strong></a> |
| Most notably, you will need Python 2 or 3 to run <code>x.py</code>.</p> |
| <p>There are no hard hardware requirements, but building the compiler is |
| computationally expensive, so a beefier machine will help, and I wouldn't |
| recommend trying to build on a Raspberry Pi :P</p> |
| <ul> |
| <li>Recommended >=30GB of free disk space; otherwise, you will have to keep |
| clearing incremental caches. More space is better, the compiler is a bit of a |
| hog; it's a problem we are aware of.</li> |
| <li>Recommended >=8GB RAM.</li> |
| <li>Recommended >=2 cores; having more cores really helps.</li> |
| <li>You will need an internet connection to build; the bootstrapping process |
| involves updating git submodules and downloading a beta compiler. It doesn't |
| need to be super fast, but that can help.</li> |
| </ul> |
| <p>Building the compiler takes more than half an hour on my moderately powerful |
| laptop. The first time you build the compiler, LLVM will also be built unless |
| you use CI-built LLVM (<a href="#configuring-the-compiler">see below</a>).</p> |
| <p>Like <code>cargo</code>, the build system will use as many cores as possible. Sometimes |
| this can cause you to run low on memory. You can use <code>-j</code> to adjust the number |
| concurrent jobs. If a full build takes more than ~45 minutes to an hour, |
| you are probably spending most of the time swapping memory in and out; |
| try using <code>-j1</code>.</p> |
| <p>On a slow machine, the build times for rustc are very painful. Consider using |
| <code>./x.py check</code> instead of a full build and letting the automated tests run |
| when you push to GitHub.</p> |
| <p>If you don't have too much free disk space, you may want to turn off |
| incremental compilation (<a href="#configuring-the-compiler">see below</a>). This will make |
| compilation take longer (especially after a rebase), |
| but will save a ton of space from the incremental caches.</p> |
| <h3 id="cloning"><a class="header" href="#cloning">Cloning</a></h3> |
| <p>You can just do a normal git clone:</p> |
| <pre><code class="language-sh">git clone https://github.com/rust-lang/rust.git |
| </code></pre> |
| <p>You don't need to clone the submodules at this time. But if you want to, you |
| can do the following:</p> |
| <pre><code class="language-sh"># first time |
| git submodule update --init --recursive |
| |
| # subsequent times (to pull new commits) |
| git submodule update |
| </code></pre> |
| <h3 id="configuring-the-compiler"><a class="header" href="#configuring-the-compiler">Configuring the Compiler</a></h3> |
| <p>The compiler has a configuration file which contains a ton of settings. We will |
| provide some recommendations here that should work for most, but <a href="./building/how-to-build-and-run.html#create-a-configtoml">check out |
| this chapter for more info</a>.</p> |
| <p>In the top level of the repo:</p> |
| <pre><code class="language-sh">$ x.py setup |
| </code></pre> |
| <p>This will walk you through an interactive setup for x.py that looks like this:</p> |
| <pre><code>$ x.py setup |
| Welcome to the Rust project! What do you want to do with x.py? |
| a) Contribute to the standard library |
| b) Contribute to the compiler |
| c) Contribute to the compiler, and also modify LLVM or codegen |
| d) Install Rust from source |
| Please choose one (a/b/c/d): a |
| `x.py` will now use the configuration at /home/joshua/rustc2/src/bootstrap/defaults/config.toml.library |
| To get started, try one of the following commands: |
| - `x.py check` |
| - `x.py build` |
| - `x.py test library/std` |
| - `x.py doc` |
| For more suggestions, see https://rustc-dev-guide.rust-lang.org/building/suggested.html |
| </code></pre> |
| <p>Note that by default, <code>x.py setup</code> will use CI-built LLVM if available for your |
| platform so that you don't need to build LLVM in addition to building the |
| compiler. In some circumstances, such as when updating the version of LLVM used |
| by <code>rustc</code>, you may want to temporarily disable this feature. See the <a href="https://rustc-dev-guide.rust-lang.org/backend/updating-llvm.html?highlight=download-ci-llvm#feature-updates">"Updating |
| LLVM" section</a> for more.</p> |
| <p>If you want to download LLVM from CI without running <code>x.py setup</code>, you can set |
| the <code>download-ci-llvm</code> option to <code>true</code> in your <code>config.toml</code>:</p> |
| <pre><code class="language-toml">[llvm] |
| download-ci-llvm = true |
| </code></pre> |
| <h3 id="xpy-intro"><a class="header" href="#xpy-intro">x.py Intro</a></h3> |
| <p><code>rustc</code> is a <em>bootstrapping</em> compiler, which means that it is written in Rust |
| and thus needs to be compiled by itself. So where do you |
| get the original compiler from? We use the current beta compiler |
| to build a new compiler. Then, we use that compiler to build itself. Thus, |
| <code>rustc</code> has a 2-stage build. You can read more about bootstrapping |
| <a href="./building/bootstrapping.html">here</a>, but you don't need to know much more to contribute.</p> |
| <p>We have a special tool <code>./x.py</code> that drives this process. It is used for |
| building the compiler, the standard libraries, and <code>rustdoc</code>. It is also used |
| for driving CI and building the final release artifacts.</p> |
| <p>Unfortunately, a proper 2-stage build takes a long time depending on your |
| hardware, but it is the only correct way to build everything (e.g. it's what |
| the CI and release processes use). <strong>However, in most cases, you can get by |
| without a full 2-stage build</strong>. In the following section, we give instructions |
| for how to do "the correct thing", but then we also give various tips to speed |
| things up.</p> |
| <h3 id="building-and-testing-rustc"><a class="header" href="#building-and-testing-rustc">Building and Testing <code>rustc</code></a></h3> |
| <p>Here is a summary of the different commands for reference, but you probably |
| should still read the rest of the section:</p> |
| <table><thead><tr><th>Command</th><th>When to use it</th></tr></thead><tbody> |
| <tr><td><code>x.py check</code></td><td>Quick check to see if things compile; <a href="./building/suggested.html#configuring-rust-analyzer-for-rustc">rust-analyzer can run this automatically for you</a></td></tr> |
| <tr><td><code>x.py build --stage 0 [library/std]</code></td><td>Build only the standard library, without building the compiler</td></tr> |
| <tr><td><code>x.py build library/std</code></td><td>Build just the 1st stage of the compiler, along with the standard library; this is faster than building stage 2 and usually good enough</td></tr> |
| <tr><td><code>x.py build --keep-stage 1 library/std</code></td><td>Build the 1st stage of the compiler and skips rebuilding the standard library; this is useful after you've done an ordinary stage1 build to skip compilation time, but it can cause weird problems. (Just do a regular build to resolve.)</td></tr> |
| <tr><td><code>x.py test [--keep-stage 1]</code></td><td>Run the test suite using the stage1 compiler</td></tr> |
| <tr><td><code>x.py test --bless [--keep-stage 1]</code></td><td>Run the test suite using the stage1 compiler <em>and</em> update expected test output.</td></tr> |
| <tr><td><code>x.py build --stage 2 compiler/rustc</code></td><td>Do a full 2-stage build. You almost never want to do this.</td></tr> |
| <tr><td><code>x.py test --stage 2</code></td><td>Do a full 2-stage build and run all tests. You almost never want to do this.</td></tr> |
| </tbody></table> |
| <p>To do a full 2-stage build of the whole compiler, you should run this (after |
| updating <code>config.toml</code> as mentioned above):</p> |
| <pre><code class="language-sh">./x.py build --stage 2 compiler/rustc |
| </code></pre> |
| <p>In the process, this will also necessarily build the standard libraries, and it |
| will build <code>rustdoc</code> (which doesn't take too long).</p> |
| <p>To build and test everything:</p> |
| <pre><code class="language-sh">./x.py test |
| </code></pre> |
| <p>For most contributions, you only need to build stage 1, which saves a lot of time:</p> |
| <pre><code class="language-sh"># Build the compiler (stage 1) |
| ./x.py build library/std |
| |
| # Subsequent builds |
| ./x.py build --keep-stage 1 library/std |
| </code></pre> |
| <p>This will take a while, especially the first time. Be wary of accidentally |
| touching or formatting the compiler, as <code>./x.py</code> will try to recompile it.</p> |
| <p><strong>NOTE</strong>: The <code>--keep-stage 1</code> will <em>assume</em> that the stage 0 standard library |
| does not need to be rebuilt, which is usually true, which will save some time. |
| However, if you are changing certain parts of the compiler, this may lead to |
| weird errors. Feel free to ask on <a href="https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler">zulip</a> if you are running into issues.</p> |
| <p>This runs a ton of tests and takes a long time to complete. If you are |
| working on <code>rustc</code>, you can usually get by with only the <a href="./tests/adding.html#ui">UI tests</a>. These |
| test are mostly for the frontend of the compiler, so if you are working on LLVM |
| or codegen, this shortcut will <em>not</em> test your changes. You can read more about the |
| different test suites <a href="https://rustc-dev-guide.rust-lang.org/tests/intro.html">in this chapter</a>.</p> |
| <pre><code class="language-sh"># First build |
| ./x.py test src/test/ui |
| |
| # Subsequent builds |
| ./x.py test src/test/ui --keep-stage 1 |
| </code></pre> |
| <p>If your changes impact test output, you can use <code>--bless</code> to automatically |
| update the <code>.stderr</code> files of the affected tests:</p> |
| <pre><code class="language-sh">./x.py test src/test/ui --keep-stage 1 --bless |
| </code></pre> |
| <p>While working on the compiler, it can be helpful to see if the code just |
| compiles (similar to <code>cargo check</code>) without actually building it. You can do |
| this with:</p> |
| <pre><code class="language-sh">./x.py check |
| </code></pre> |
| <p>This command is really fast (relative to the other commands). It usually |
| completes in a couple of minutes on my laptop. <strong>A common workflow when working |
| on the compiler is to make changes and repeatedly check with <code>./x.py check</code>. |
| Then, run the tests as shown above when you think things should work.</strong></p> |
| <p>Finally, the CI ensures that the codebase is using consistent style. To format |
| the code:</p> |
| <pre><code class="language-sh"># Actually format |
| ./x.py fmt |
| |
| # Just check formatting, exit with error |
| ./x.py fmt --check |
| </code></pre> |
| <p><em>Note</em>: we don't use stable <code>rustfmt</code>; we use a pinned version with a special |
| config, so this may result in different style from normal <code>rustfmt</code> if you have |
| format-on-save turned on. It's a good habit to run <code>./x.py fmt</code> before every |
| commit, as this reduces conflicts later. The pinned version is built under |
| <code>build/<target>/stage0/bin/rustfmt</code>, so if you want, you can use it for a |
| single file or for format-on-save in your editor, which can be faster than <code>./x.py fmt</code>. |
| You'll have to pass the <!-- date: 2021-09 --> <code>--edition=2021</code> argument |
| yourself when calling <code>rustfmt</code> directly.</p> |
| <p>One last thing: you can use <code>RUSTC_LOG=XXX</code> to get debug logging. <a href="./tracing.html">Read more |
| here</a>. Notice the <code>C</code> in <code>RUSTC_LOG</code>. Other than that, it uses normal |
| <a href="https://crates.io/crates/env_logger"><code>env_logger</code></a> or <code>tracing</code> syntax.</p> |
| <h3 id="building-and-testing-stdcorealloctestproc_macroetc"><a class="header" href="#building-and-testing-stdcorealloctestproc_macroetc">Building and Testing <code>std</code>/<code>core</code>/<code>alloc</code>/<code>test</code>/<code>proc_macro</code>/etc.</a></h3> |
| <p>As before, technically the proper way to build one of these libraries is to use |
| the stage-2 compiler, which of course requires a 2-stage build, described above |
| (<code>./x.py build</code>).</p> |
| <p>In practice, though, you don't need to build the compiler unless you are |
| planning to use a recently added nightly feature. Instead, you can just build |
| stage 0, which uses the current beta compiler.</p> |
| <pre><code class="language-sh">./x.py build --stage 0 |
| </code></pre> |
| <pre><code class="language-sh">./x.py test --stage 0 library/std |
| </code></pre> |
| <p>(The same works for <code>library/alloc</code>, <code>library/core</code>, etc.)</p> |
| <h3 id="building-and-testing-rustdoc"><a class="header" href="#building-and-testing-rustdoc">Building and Testing <code>rustdoc</code></a></h3> |
| <p><code>rustdoc</code> uses <code>rustc</code> internals (and, of course, the standard library), so you |
| will have to build the compiler and <code>std</code> once before you can build <code>rustdoc</code>. |
| As before, you can use <code>./x.py build</code> to do this. The first time you build, |
| the stage-1 compiler will also be built.</p> |
| <pre><code class="language-sh"># First build |
| ./x.py build |
| |
| # Subsequent builds |
| ./x.py build --keep-stage 1 |
| </code></pre> |
| <p>As with the compiler, you can do a fast check build:</p> |
| <pre><code class="language-sh">./x.py check |
| </code></pre> |
| <p>Rustdoc has two types of tests: content tests and UI tests.</p> |
| <pre><code class="language-sh"># Content tests |
| ./x.py test src/test/rustdoc |
| |
| # UI tests |
| ./x.py test src/test/rustdoc-ui |
| |
| # Both at once |
| ./x.py test src/test/rustdoc src/test/rustdoc-ui |
| </code></pre> |
| <h3 id="contributing-code-to-other-rust-projects"><a class="header" href="#contributing-code-to-other-rust-projects">Contributing code to other Rust projects</a></h3> |
| <p>There are a bunch of other projects that you can contribute to outside of the |
| <code>rust-lang/rust</code> repo, including <code>clippy</code>, <code>miri</code>, <code>chalk</code>, and many others.</p> |
| <p>These repos might have their own contributing guidelines and procedures. Many |
| of them are owned by working groups (e.g. <code>chalk</code> is largely owned by |
| WG-traits). For more info, see the documentation in those repos' READMEs.</p> |
| <h3 id="other-ways-to-contribute"><a class="header" href="#other-ways-to-contribute">Other ways to contribute</a></h3> |
| <p>There are a bunch of other ways you can contribute, especially if you don't |
| feel comfortable jumping straight into the large <code>rust-lang/rust</code> codebase.</p> |
| <p>The following tasks are doable without much background knowledge but are |
| incredibly helpful:</p> |
| <ul> |
| <li><a href="./notification-groups/cleanup-crew.html">Cleanup crew</a>: find minimal reproductions of ICEs, bisect |
| regressions, etc. This is a way of helping that saves a ton of time for |
| others to fix an error later.</li> |
| <li><a href="./contributing.html#writing-documentation">Writing documentation</a>: if you are feeling a bit more intrepid, you could try |
| to read a part of the code and write doc comments for it. This will help you |
| to learn some part of the compiler while also producing a useful artifact!</li> |
| <li><a href="https://rust-lang.github.io/compiler-team/working-groups/">Working groups</a>: there are a bunch of working groups on a wide variety |
| of rust-related things.</li> |
| </ul> |
| <h2 id="contributor-procedures"><a class="header" href="#contributor-procedures">Contributor Procedures</a></h2> |
| <p>There are some official procedures to know about. This is a tour of the |
| highlights, but there are a lot more details, which we will link to below.</p> |
| <h3 id="code-review"><a class="header" href="#code-review">Code Review</a></h3> |
| <p>When you open a PR on the <code>rust-lang/rust</code> repo, a bot called <code>@rust-highfive</code> will |
| automatically assign a reviewer to the PR. The reviewer is the person that will |
| approve the PR to be tested and merged. If you want a specific reviewer (e.g. a |
| team member you've been working with), you can specifically request them by |
| writing <code>r? @user</code> (e.g. <code>r? @eddyb</code>) in either the original post or a followup |
| comment (you can see <a href="https://github.com/rust-lang/rust/pull/78133#issuecomment-712692371">this comment</a> for example).</p> |
| <p>Please note that the reviewers are humans, who for the most part work on <code>rustc</code> |
| in their free time. This means that they can take some time to respond and review |
| your PR. It also means that reviewers can miss some PRs that are assigned to them.</p> |
| <p>To try to move PRs forward, the Triage WG regularly goes through all PRs that |
| are waiting for review and haven't been discussed for at least 2 weeks. If you |
| don't get a review within 2 weeks, feel free to ask the Triage WG on |
| Zulip (<a href="https://rust-lang.zulipchat.com/#narrow/stream/242269-t-release.2Ftriage">#t-release/triage</a>). They have knowledge of when to ping, who might be |
| on vacation, etc.</p> |
| <p>The reviewer may request some changes using the GitHub code review interface. |
| They may also request special procedures (such as a <a href="https://github.com/rust-lang/crater">crater</a> run; <a href="#breaking-changes">see |
| below</a>) for some PRs.</p> |
| <p>When the PR is ready to be merged, the reviewer will issue a command to |
| <code>@bors</code>, the CI bot. Usually, this is <code>@bors r+</code> or <code>@bors r=user</code> to approve |
| a PR (there are few other commands, but they are less relevant here). |
| You can see <a href="https://github.com/rust-lang/rust/pull/78133#issuecomment-712726339">this comment</a> for example. This puts the PR in <a href="https://bors.rust-lang.org/queue/rust">bors's queue</a> |
| to be tested and merged. Be patient; this can take a while and the queue can |
| sometimes be long. PRs are never merged by hand.</p> |
| <h3 id="bug-fixes-or-normal-code-changes"><a class="header" href="#bug-fixes-or-normal-code-changes">Bug Fixes or "Normal" code changes</a></h3> |
| <p>For most PRs, no special procedures are needed. You can just open a PR, and it |
| will be reviewed, approved, and merged. This includes most bug fixes, |
| refactorings, and other user-invisible changes. The next few sections talk |
| about exceptions to this rule.</p> |
| <p>Also, note that it is perfectly acceptable to open WIP PRs or GitHub <a href="https://github.blog/2019-02-14-introducing-draft-pull-requests/">Draft |
| PRs</a>. Some people prefer to do this so they can get feedback along the |
| way or share their code with a collaborator. Others do this so they can utilize |
| the CI to build and test their PR (e.g. if you are developing on a laptop).</p> |
| <h3 id="new-features"><a class="header" href="#new-features">New Features</a></h3> |
| <p>Rust has strong backwards-compatibility guarantees. Thus, new features can't |
| just be implemented directly in stable Rust. Instead, we have 3 release |
| channels: stable, beta, and nightly.</p> |
| <ul> |
| <li><strong>Stable</strong>: this is the latest stable release for general usage.</li> |
| <li><strong>Beta</strong>: this is the next release (will be stable within 6 weeks).</li> |
| <li><strong>Nightly</strong>: follows the <code>master</code> branch of the repo. This is the only |
| channel where unstable, incomplete, or experimental features are usable with |
| feature gates.</li> |
| </ul> |
| <p>In order to implement a new feature, usually you will need to go through <a href="https://github.com/rust-lang/rfcs/blob/master/README.md">the |
| RFC process</a> to propose a design, have discussions, etc. In some cases, |
| small features can be added with only an FCP (<a href="#breaking-changes">see below</a>). If in doubt, ask the |
| compiler, language, or libs team (whichever is most relevant).</p> |
| <p>After a feature is approved to be added, a tracking issue is created on the |
| <code>rust-lang/rust</code> repo, which tracks the progress towards the implementation of |
| the feature, any bugs reported, and eventually stabilization.</p> |
| <p>The feature then needs to be implemented behind a feature gate, which prevents |
| it from being accidentally used.</p> |
| <p>Finally, somebody may propose stabilizing the feature in an upcoming version of |
| Rust. This requires a Final Comment Period (<a href="#breaking-changes">see below</a>) to get the |
| approval of the relevant teams.</p> |
| <p>After that, the feature gate can be removed and the feature turned on for all users.</p> |
| <p>For more details on this process, see <a href="./implementing_new_features.html">this chapter on implementing new |
| features.</a></p> |
| <h3 id="breaking-changes"><a class="header" href="#breaking-changes">Breaking Changes</a></h3> |
| <p>As mentioned above, Rust has strong backwards-compatibility guarantees. To this |
| end, we are reluctant to make breaking changes. However, sometimes they are |
| needed to correct compiler bugs (e.g. code that compiled but should not) or |
| make progress on some features.</p> |
| <p>Depending on the scale of the breakage, there are a few different actions that |
| can be taken. If the reviewer believes the breakage is very minimal (i.e. very |
| unlikely to be actually encountered by users), they may just merge the change. |
| More often, they will request a Final Comment Period (FCP), which calls for |
| rough consensus among the members of a relevant team. The team members can |
| discuss the issue and either accept, reject, or request changes on the PR.</p> |
| <p>If the scale of breakage is large, a deprecation warning may be needed. This is |
| a warning that the compiler will display to users whose code will break in the |
| future. After some time, an FCP can be used to move forward with the actual |
| breakage.</p> |
| <p>If the scale of breakage is unknown, a team member or contributor may request a |
| <a href="https://github.com/rust-lang/crater">crater</a> run. This is a bot that will compile all crates.io crates and many |
| public github repos with the compiler with your changes. A report will then be |
| generated with crates that ceased to compile with or began to compile with your |
| changes. Crater runs can take a few days to complete.</p> |
| <h3 id="major-changes"><a class="header" href="#major-changes">Major Changes</a></h3> |
| <p>The compiler team has a special process for large changes, whether or not they |
| cause breakage. This process is called a Major Change Proposal (MCP). MCP is a |
| relatively lightweight mechanism for getting feedback on large changes to the |
| compiler (as opposed to a full RFC or a design meeting with the team).</p> |
| <p>Example of things that might require MCPs include major refactorings, changes |
| to important types, or important changes to how the compiler does something, or |
| smaller user-facing changes.</p> |
| <p><strong>When in doubt, ask on <a href="https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler">zulip</a>. It would be a shame to put a lot of work |
| into a PR that ends up not getting merged!</strong> <a href="https://forge.rust-lang.org/compiler/mcp.html">See this document</a> for |
| more info on MCPs.</p> |
| <h3 id="performance"><a class="header" href="#performance">Performance</a></h3> |
| <p>Compiler performance is important. We have put a lot of effort over the last |
| few years into <a href="https://perf.rust-lang.org/dashboard.html">gradually improving it</a>.</p> |
| <p>If you suspect that your change may cause a performance regression (or |
| improvement), you can request a "perf run" (your reviewer may also request one |
| before approving). This is yet another bot that will compile a collection of |
| benchmarks on a compiler with your changes. The numbers are reported |
| <a href="https://perf.rust-lang.org">here</a>, and you can see a comparison of your changes against the latest |
| master.</p> |
| <h2 id="other-resources"><a class="header" href="#other-resources">Other Resources</a></h2> |
| <ul> |
| <li>This guide: talks about how <code>rustc</code> works</li> |
| <li><a href="https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler">The t-compiler zulip</a></li> |
| <li><a href="https://doc.rust-lang.org/nightly/nightly-rustc/">The compiler's documentation (rustdocs)</a></li> |
| <li><a href="https://forge.rust-lang.org/">The Forge</a> has more documentation about various procedures.</li> |
| <li><code>#contribute</code> and <code>#rustdoc</code> on <a href="https://discord.gg/rust-lang">Discord</a>.</li> |
| </ul> |
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