2 [contributing-to-rust]: #contributing-to-rust
4 Thank you for your interest in contributing to Rust! There are many ways to
5 contribute, and we appreciate all of them. This document is a bit long, so here's
6 links to the major sections:
8 * [Feature Requests](#feature-requests)
9 * [Bug Reports](#bug-reports)
10 * [The Build System](#the-build-system)
11 * [Pull Requests](#pull-requests)
12 * [Writing Documentation](#writing-documentation)
13 * [Issue Triage](#issue-triage)
14 * [Out-of-tree Contributions](#out-of-tree-contributions)
15 * [Helpful Links and Information](#helpful-links-and-information)
17 If you have questions, please make a post on [internals.rust-lang.org][internals] or
18 hop on [#rust-internals][pound-rust-internals].
20 As a reminder, all contributors are expected to follow our [Code of Conduct][coc].
22 [pound-rust-internals]: https://chat.mibbit.com/?server=irc.mozilla.org&channel=%23rust-internals
23 [internals]: https://internals.rust-lang.org
24 [coc]: https://www.rust-lang.org/conduct.html
27 [feature-requests]: #feature-requests
29 To request a change to the way that the Rust language works, please open an
30 issue in the [RFCs repository](https://github.com/rust-lang/rfcs/issues/new)
31 rather than this one. New features and other significant language changes
32 must go through the RFC process.
35 [bug-reports]: #bug-reports
37 While bugs are unfortunate, they're a reality in software. We can't fix what we
38 don't know about, so please report liberally. If you're not sure if something
39 is a bug or not, feel free to file a bug anyway.
41 **If you believe reporting your bug publicly represents a security risk to Rust users,
42 please follow our [instructions for reporting security vulnerabilities](https://www.rust-lang.org/security.html)**.
44 If you have the chance, before reporting a bug, please [search existing
45 issues](https://github.com/rust-lang/rust/search?q=&type=Issues&utf8=%E2%9C%93),
46 as it's possible that someone else has already reported your error. This doesn't
47 always work, and sometimes it's hard to know what to search for, so consider this
48 extra credit. We won't mind if you accidentally file a duplicate report.
50 Opening an issue is as easy as following [this
51 link](https://github.com/rust-lang/rust/issues/new) and filling out the fields.
52 Here's a template that you can use to file a bug, though it's not necessary to
55 <short summary of the bug>
59 <code sample that causes the bug>
61 I expected to see this happen: <explanation>
63 Instead, this happened: <explanation>
67 `rustc --version --verbose`:
71 All three components are important: what you did, what you expected, what
72 happened instead. Please include the output of `rustc --version --verbose`,
73 which includes important information about what platform you're on, what
74 version of Rust you're using, etc.
76 Sometimes, a backtrace is helpful, and so including that is nice. To get
77 a backtrace, set the `RUST_BACKTRACE` environment variable to a value
78 other than `0`. The easiest way
79 to do this is to invoke `rustc` like this:
82 $ RUST_BACKTRACE=1 rustc ...
86 [the-build-system]: #the-build-system
88 Rust's build system allows you to bootstrap the compiler, run tests &
89 benchmarks, generate documentation, install a fresh build of Rust, and more.
90 It's your best friend when working on Rust, allowing you to compile & test
91 your contributions before submission.
93 The build system lives in [the `src/bootstrap` directory][bootstrap] in the
94 project root. Our build system is itself written in Rust and is based on Cargo
95 to actually build all the compiler's crates. If you have questions on the build
96 system internals, try asking in [`#rust-internals`][pound-rust-internals].
98 [bootstrap]: https://github.com/rust-lang/rust/tree/master/src/bootstrap/
101 [configuration]: #configuration
103 Before you can start building the compiler you need to configure the build for
104 your system. In most cases, that will just mean using the defaults provided
107 To change configuration, you must copy the file `config.toml.example`
108 to `config.toml` in the directory from which you will be running the build, and
109 change the settings provided.
111 There are large number of options provided in this config file that will alter the
112 configuration used in the build process. Some options to note:
115 - `ccache = true` - Use ccache when building llvm
118 - `compiler-docs = true` - Build compiler documentation
121 - `debuginfo = true` - Build a compiler with debuginfo
122 - `optimize = false` - Disable optimizations to speed up compilation of stage1 rust
124 For more options, the `config.toml` file contains commented out defaults, with
125 descriptions of what each option will do.
127 Note: Previously the `./configure` script was used to configure this
128 project. It can still be used, but it's recommended to use a `config.toml`
129 file. If you still have a `config.mk` file in your directory - from
130 `./configure` - you may need to delete it for `config.toml` to work.
133 [building]: #building
136 - [build dependencies](README.md#building-from-source)
137 - `gdb` 6.2.0 minimum, 7.1 or later recommended for test builds
139 The build system uses the `x.py` script to control the build process. This script
140 is used to build, test, and document various parts of the compiler. You can
147 On some systems you can also use the shorter version:
153 To learn more about the driver and top-level targets, you can execute:
159 The general format for the driver script is:
162 python x.py <command> [<directory>]
165 Some example commands are `build`, `test`, and `doc`. These will build, test,
166 and document the specified directory. The second argument, `<directory>`, is
167 optional and defaults to working over the entire compiler. If specified,
168 however, only that specific directory will be built. For example:
171 # build the entire compiler
174 # build all documentation
177 # run all test suites
180 # build only the standard library
181 python x.py build src/libstd
183 # test only one particular test suite
184 python x.py test src/test/rustdoc
186 # build only the stage0 libcore library
187 python x.py build src/libcore --stage 0
190 You can explore the build system through the various `--help` pages for each
191 subcommand. For example to learn more about a command you can run:
194 python x.py build --help
197 To learn about all possible rules you can execute, run:
200 python x.py build --help --verbose
203 Note: Previously `./configure` and `make` were used to build this project.
204 They are still available, but `x.py` is the recommended build system.
207 [useful-commands]: #useful-commands
209 Some common invocations of `x.py` are:
211 - `x.py build --help` - show the help message and explain the subcommand
212 - `x.py build src/libtest --stage 1` - build up to (and including) the first
213 stage. For most cases we don't need to build the stage2 compiler, so we can
214 save time by not building it. The stage1 compiler is a fully functioning
215 compiler and (probably) will be enough to determine if your change works as
217 - `x.py build src/rustc --stage 1` - This will build just rustc, without libstd.
218 This is the fastest way to recompile after you changed only rustc source code.
219 Note however that the resulting rustc binary won't have a stdlib to link
220 against by default. You can build libstd once with `x.py build src/libstd`,
221 but it is only guaranteed to work if recompiled, so if there are any issues
223 - `x.py test` - build the full compiler & run all tests (takes a while). This
224 is what gets run by the continuous integration system against your pull
225 request. You should run this before submitting to make sure your tests pass
226 & everything builds in the correct manner.
227 - `x.py test src/libstd --stage 1` - test the standard library without
229 - `x.py test src/test/run-pass --test-args TESTNAME` - Run a matching set of
231 - `TESTNAME` should be a substring of the tests to match against e.g. it could
232 be the fully qualified test name, or just a part of it.
233 `TESTNAME=collections::hash::map::test_map::test_capacity_not_less_than_len`
234 or `TESTNAME=test_capacity_not_less_than_len`.
235 - `x.py test src/test/run-pass --stage 1 --test-args <substring-of-test-name>` -
236 Run a single rpass test with the stage1 compiler (this will be quicker than
237 running the command above as we only build the stage1 compiler, not the entire
238 thing). You can also leave off the directory argument to run all stage1 test
240 - `x.py test src/libcore --stage 1` - Run stage1 tests in `libcore`.
241 - `x.py test src/tools/tidy` - Check that the source code is in compliance with
242 Rust's style guidelines. There is no official document describing Rust's full
243 guidelines as of yet, but basic rules like 4 spaces for indentation and no
244 more than 99 characters in a single line should be kept in mind when writing
247 ### Using your local build
248 [using-local-build]: #using-local-build
250 If you use Rustup to manage your rust install, it has a feature called ["custom
251 toolchains"][toolchain-link] that you can use to access your newly-built compiler
252 without having to install it to your system or user PATH. If you've run `python
253 x.py build`, then you can add your custom rustc to a new toolchain like this:
255 [toolchain-link]: https://github.com/rust-lang-nursery/rustup.rs#working-with-custom-toolchains-and-local-builds
258 rustup toolchain link <name> build/<host-triple>/stage2
261 Where `<host-triple>` is the build triple for the host (the triple of your
262 computer, by default), and `<name>` is the name for your custom toolchain. (If you
263 added `--stage 1` to your build command, the compiler will be in the `stage1`
264 folder instead.) You'll only need to do this once - it will automatically point
265 to the latest build you've done.
267 Once this is set up, you can use your custom toolchain just like any other. For
268 example, if you've named your toolchain `local`, running `cargo +local build` will
269 compile a project with your custom rustc, setting `rustup override set local` will
270 override the toolchain for your current directory, and `cargo +local doc` will use
271 your custom rustc and rustdoc to generate docs. (If you do this with a `--stage 1`
272 build, you'll need to build rustdoc specially, since it's not normally built in
273 stage 1. `python x.py build --stage 1 src/libstd src/tools/rustdoc` will build
274 rustdoc and libstd, which will allow rustdoc to be run with that toolchain.)
277 [pull-requests]: #pull-requests
279 Pull requests are the primary mechanism we use to change Rust. GitHub itself
280 has some [great documentation][pull-requests] on using the Pull Request feature.
281 We use the "fork and pull" model [described here][development-models], where
282 contributors push changes to their personal fork and create pull requests to
283 bring those changes into the source repository.
285 [pull-requests]: https://help.github.com/articles/about-pull-requests/
286 [development-models]: https://help.github.com/articles/about-collaborative-development-models/
288 Please make pull requests against the `master` branch.
290 Compiling all of `./x.py test` can take a while. When testing your pull request,
291 consider using one of the more specialized `./x.py` targets to cut down on the
292 amount of time you have to wait. You need to have built the compiler at least
293 once before running these will work, but that’s only one full build rather than
296 $ python x.py test --stage 1
298 is one such example, which builds just `rustc`, and then runs the tests. If
299 you’re adding something to the standard library, try
301 $ python x.py test src/libstd --stage 1
303 Please make sure your pull request is in compliance with Rust's style
304 guidelines by running
306 $ python x.py test src/tools/tidy
308 Make this check before every pull request (and every new commit in a pull
309 request) ; you can add [git hooks](https://git-scm.com/book/en/v2/Customizing-Git-Git-Hooks)
310 before every push to make sure you never forget to make this check.
312 All pull requests are reviewed by another person. We have a bot,
313 @rust-highfive, that will automatically assign a random person to review your
316 If you want to request that a specific person reviews your pull request,
317 you can add an `r?` to the message. For example, Steve usually reviews
318 documentation changes. So if you were to make a documentation change, add
322 to the end of the message, and @rust-highfive will assign @steveklabnik instead
323 of a random person. This is entirely optional.
325 After someone has reviewed your pull request, they will leave an annotation
326 on the pull request with an `r+`. It will look something like this:
330 This tells @bors, our lovable integration bot, that your pull request has
331 been approved. The PR then enters the [merge queue][merge-queue], where @bors
332 will run all the tests on every platform we support. If it all works out,
333 @bors will merge your code into `master` and close the pull request.
335 [merge-queue]: https://buildbot2.rust-lang.org/homu/queue/rust
337 Speaking of tests, Rust has a comprehensive test suite. More information about
339 [here](https://github.com/rust-lang/rust-wiki-backup/blob/master/Note-testsuite.md).
341 ### External Dependencies
342 [external-dependencies]: #external-dependencies
344 Currently building Rust will also build the following external projects:
346 * [clippy](https://github.com/rust-lang-nursery/rust-clippy)
347 * [miri](https://github.com/solson/miri)
349 If your changes break one of these projects, you need to fix them by opening
350 a pull request against the broken project asking to put the fix on a branch.
351 Then you can disable the tool building via `src/tools/toolstate.toml`.
352 Once the branch containing your fix is likely to be merged, you can point
353 the affected submodule at this branch.
355 Don't forget to also add your changes with
358 git add path/to/submodule
361 outside the submodule.
363 In order to prepare your PR, you can run the build locally by doing
364 `./x.py build src/tools/TOOL`. If you will be editing the sources
365 there, you may wish to set `submodules = false` in the `config.toml`
366 to prevent `x.py` from resetting to the original branch.
368 #### Breaking Tools Built With The Compiler
369 [breaking-tools-built-with-the-compiler]: #breaking-tools-built-with-the-compiler
371 Rust's build system builds a number of tools that make use of the
372 internals of the compiler. This includes clippy,
373 [RLS](https://github.com/rust-lang-nursery/rls) and
374 [rustfmt](https://github.com/rust-lang-nursery/rustfmt). If these tools
375 break because of your changes, you may run into a sort of "chicken and egg"
376 problem. These tools rely on the latest compiler to be built so you can't update
377 them to reflect your changes to the compiler until those changes are merged into
378 the compiler. At the same time, you can't get your changes merged into the compiler
379 because the rust-lang/rust build won't pass until those tools build and pass their
382 That means that, in the default state, you can't update the compiler without first
383 fixing rustfmt, rls and the other tools that the compiler builds.
385 Luckily, a feature was [added to Rust's build](https://github.com/rust-lang/rust/pull/45243)
386 to make all of this easy to handle. The idea is that you mark the tools as "broken",
387 so that the rust-lang/rust build passes without trying to build them, then land the change
388 in the compiler, wait for a nightly, and go update the tools that you broke. Once you're done
389 and the tools are working again, you go back in the compiler and change the tools back
392 This should avoid a bunch of synchronization dances and is also much easier on contributors as
393 there's no need to block on rls/rustfmt/other tools changes going upstream.
395 Here are those same steps in detail:
397 1. (optional) First, if it doesn't exist already, create a `config.toml` by copying
398 `config.toml.example` in the root directory of the Rust repository.
399 Set `submodules = false` in the `[build]` section. This will prevent `x.py`
400 from resetting to the original branch after you make your changes. If you
401 need to [update any submodules to their latest versions][updating-submodules],
402 see the section of this file about that for more information.
403 2. (optional) Run `./x.py test src/tools/rustfmt` (substituting the submodule
404 that broke for `rustfmt`). Fix any errors in the submodule (and possibly others).
405 3. (optional) Make commits for your changes and send them to upstream repositories as a PR.
406 4. (optional) Maintainers of these submodules will **not** merge the PR. The PR can't be
407 merged because CI will be broken. You'll want to write a message on the PR referencing
408 your change, and how the PR should be merged once your change makes it into a nightly.
409 5. Update `src/tools/toolstate.toml` to indicate that the tool in question is "broken",
410 that will disable building it on CI. See the documentation in that file for the exact
411 configuration values you can use.
412 6. Commit the changes to `src/tools/toolstate.toml`, **do not update submodules in your commit**,
413 and then update the PR you have for rust-lang/rust.
414 7. Wait for your PR to merge.
415 8. Wait for a nightly
416 9. (optional) Help land your PR on the upstream repository now that your changes are in nightly.
417 10. (optional) Send a PR to rust-lang/rust updating the submodule, reverting `src/tools/toolstate.toml` back to a "building" or "testing" state.
419 #### Updating submodules
420 [updating-submodules]: #updating-submodules
422 These instructions are specific to updating `rustfmt`, however they may apply
423 to the other submodules as well. Please help by improving these instructions
424 if you find any discrepencies or special cases that need to be addressed.
426 To update the `rustfmt` submodule, start by running the appropriate
427 [`git submodule` command](https://git-scm.com/book/en/v2/Git-Tools-Submodules).
428 For example, to update to the latest commit on the remote master branch,
431 git submodule update --remote src/tools/rustfmt
433 If you run `./x.py build` now, and you are lucky, it may just work. If you see
434 an error message about patches that did not resolve to any crates, you will need
435 to complete a few more steps which are outlined with their rationale below.
437 *(This error may change in the future to include more information.)*
439 error: failed to resolve patches for `https://github.com/rust-lang-nursery/rustfmt`
442 patch for `rustfmt-nightly` in `https://github.com/rust-lang-nursery/rustfmt` did not resolve to any crates
443 failed to run: ~/rust/build/x86_64-unknown-linux-gnu/stage0/bin/cargo build --manifest-path ~/rust/src/bootstrap/Cargo.toml
446 If you haven't used the `[patch]`
447 section of `Cargo.toml` before, there is [some relevant documentation about it
448 in the cargo docs](http://doc.crates.io/manifest.html#the-patch-section). In
449 addition to that, you should read the
450 [Overriding dependencies](http://doc.crates.io/specifying-dependencies.html#overriding-dependencies)
451 section of the documentation as well.
453 Specifically, the following [section in Overriding dependencies](http://doc.crates.io/specifying-dependencies.html#testing-a-bugfix) reveals what the problem is:
455 > Next up we need to ensure that our lock file is updated to use this new version of uuid so our project uses the locally checked out copy instead of one from crates.io. The way [patch] works is that it'll load the dependency at ../path/to/uuid and then whenever crates.io is queried for versions of uuid it'll also return the local version.
457 > This means that the version number of the local checkout is significant and will affect whether the patch is used. Our manifest declared uuid = "1.0" which means we'll only resolve to >= 1.0.0, < 2.0.0, and Cargo's greedy resolution algorithm also means that we'll resolve to the maximum version within that range. Typically this doesn't matter as the version of the git repository will already be greater or match the maximum version published on crates.io, but it's important to keep this in mind!
459 This says that when we updated the submodule, the version number in our
460 `src/tools/rustfmt/Cargo.toml` changed. The new version is different from
461 the version in `Cargo.lock`, so the build can no longer continue.
463 To resolve this, we need to update `Cargo.lock`. Luckily, cargo provides a
464 command to do this easily.
466 First, go into the `src/` directory since that is where `Cargo.toml` is in
467 the rust repository. Then run, `cargo update -p rustfmt-nightly` to solve
472 $ cargo update -p rustfmt-nightly
475 This should change the version listed in `src/Cargo.lock` to the new version you updated
476 the submodule to. Running `./x.py build` should work now.
478 ## Writing Documentation
479 [writing-documentation]: #writing-documentation
481 Documentation improvements are very welcome. The source of `doc.rust-lang.org`
482 is located in `src/doc` in the tree, and standard API documentation is generated
483 from the source code itself.
485 Documentation pull requests function in the same way as other pull requests,
486 though you may see a slightly different form of `r+`:
488 @bors: r+ 38fe8d2 rollup
490 That additional `rollup` tells @bors that this change is eligible for a 'rollup'.
491 To save @bors some work, and to get small changes through more quickly, when
492 @bors attempts to merge a commit that's rollup-eligible, it will also merge
493 the other rollup-eligible patches too, and they'll get tested and merged at
496 To find documentation-related issues, sort by the [T-doc label][tdoc].
498 [tdoc]: https://github.com/rust-lang/rust/issues?q=is%3Aopen%20is%3Aissue%20label%3AT-doc
500 You can find documentation style guidelines in [RFC 1574][rfc1574].
502 [rfc1574]: https://github.com/rust-lang/rfcs/blob/master/text/1574-more-api-documentation-conventions.md#appendix-a-full-conventions-text
504 In many cases, you don't need a full `./x.py doc`. You can use `rustdoc` directly
505 to check small fixes. For example, `rustdoc src/doc/reference.md` will render
506 reference to `doc/reference.html`. The CSS might be messed up, but you can
507 verify that the HTML is right.
510 [issue-triage]: #issue-triage
512 Sometimes, an issue will stay open, even though the bug has been fixed. And
513 sometimes, the original bug may go stale because something has changed in the
516 It can be helpful to go through older bug reports and make sure that they are
517 still valid. Load up an older issue, double check that it's still true, and
518 leave a comment letting us know if it is or is not. The [least recently
519 updated sort][lru] is good for finding issues like this.
521 Contributors with sufficient permissions on the Rust repo can help by adding
522 labels to triage issues:
524 * Yellow, **A**-prefixed labels state which **area** of the project an issue
527 * Magenta, **B**-prefixed labels identify bugs which are **blockers**.
529 * Dark blue, **beta-** labels track changes which need to be backported into
532 * Light purple, **C**-prefixed labels represent the **category** of an issue.
534 * Green, **E**-prefixed labels explain the level of **experience** necessary
537 * The dark blue **final-comment-period** label marks bugs that are using the
538 RFC signoff functionality of [rfcbot][rfcbot] and are currenty in the final
541 * Red, **I**-prefixed labels indicate the **importance** of the issue. The
542 [I-nominated][inom] label indicates that an issue has been nominated for
543 prioritizing at the next triage meeting.
545 * The purple **metabug** label marks lists of bugs collected by other
548 * Purple gray, **O**-prefixed labels are the **operating system** or platform
549 that this issue is specific to.
551 * Orange, **P**-prefixed labels indicate a bug's **priority**. These labels
552 are only assigned during triage meetings, and replace the [I-nominated][inom]
555 * The gray **proposed-final-comment-period** label marks bugs that are using
556 the RFC signoff functionality of [rfcbot][rfcbot] and are currently awaiting
557 signoff of all team members in order to enter the final comment period.
559 * Pink, **regression**-prefixed labels track regressions from stable to the
562 * The light orange **relnotes** label marks issues that should be documented in
563 the release notes of the next release.
565 * Gray, **S**-prefixed labels are used for tracking the **status** of pull
568 * Blue, **T**-prefixed bugs denote which **team** the issue belongs to.
570 If you're looking for somewhere to start, check out the [E-easy][eeasy] tag.
572 [inom]: https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3AI-nominated
573 [eeasy]: https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3AE-easy
574 [lru]: https://github.com/rust-lang/rust/issues?q=is%3Aissue+is%3Aopen+sort%3Aupdated-asc
575 [rfcbot]: https://github.com/dikaiosune/rust-dashboard/blob/master/RFCBOT.md
577 ## Out-of-tree Contributions
578 [out-of-tree-contributions]: #out-of-tree-contributions
580 There are a number of other ways to contribute to Rust that don't deal with
583 Answer questions in [#rust][pound-rust], or on [users.rust-lang.org][users],
584 or on [StackOverflow][so].
586 Participate in the [RFC process](https://github.com/rust-lang/rfcs).
588 Find a [requested community library][community-library], build it, and publish
589 it to [Crates.io](http://crates.io). Easier said than done, but very, very
592 [pound-rust]: http://chat.mibbit.com/?server=irc.mozilla.org&channel=%23rust
593 [users]: https://users.rust-lang.org/
594 [so]: http://stackoverflow.com/questions/tagged/rust
595 [community-library]: https://github.com/rust-lang/rfcs/labels/A-community-library
597 ## Helpful Links and Information
598 [helpful-info]: #helpful-info
600 For people new to Rust, and just starting to contribute, or even for
601 more seasoned developers, some useful places to look for information
604 * [Rust Forge][rustforge] contains additional documentation, including write-ups of how to achieve common tasks
605 * The [Rust Internals forum][rif], a place to ask questions and
606 discuss Rust's internals
607 * The [generated documentation for rust's compiler][gdfrustc]
608 * The [rust reference][rr], even though it doesn't specifically talk about Rust's internals, it's a great resource nonetheless
609 * Although out of date, [Tom Lee's great blog article][tlgba] is very helpful
610 * [rustaceans.org][ro] is helpful, but mostly dedicated to IRC
611 * The [Rust Compiler Testing Docs][rctd]
612 * For @bors, [this cheat sheet][cheatsheet] is helpful (Remember to replace `@homu` with `@bors` in the commands that you use.)
613 * **Google!** ([search only in Rust Documentation][gsearchdocs] to find types, traits, etc. quickly)
614 * Don't be afraid to ask! The Rust community is friendly and helpful.
616 [gdfrustc]: http://manishearth.github.io/rust-internals-docs/rustc/
617 [gsearchdocs]: https://www.google.com/search?q=site:doc.rust-lang.org+your+query+here
618 [rif]: http://internals.rust-lang.org
619 [rr]: https://doc.rust-lang.org/book/README.html
620 [rustforge]: https://forge.rust-lang.org/
621 [tlgba]: http://tomlee.co/2014/04/a-more-detailed-tour-of-the-rust-compiler/
622 [ro]: http://www.rustaceans.org/
623 [rctd]: ./src/test/COMPILER_TESTS.md
624 [cheatsheet]: https://buildbot2.rust-lang.org/homu/