-# rustfmt [](https://travis-ci.com/rust-lang/rustfmt) [](https://ci.appveyor.com/project/rust-lang-libs/rustfmt) [](https://crates.io/crates/rustfmt-nightly) [](https://travis-ci.org/davidalber/rustfmt-travis)
+# The Rust Programming Language
-A tool for formatting Rust code according to style guidelines.
+This is the main source code repository for [Rust]. It contains the compiler,
+standard library, and documentation.
-If you'd like to help out (and you should, it's a fun project!), see
-[Contributing.md](Contributing.md) and our [Code of
-Conduct](CODE_OF_CONDUCT.md).
+[Rust]: https://www.rust-lang.org/
-You can use rustfmt in Travis CI builds. We provide a minimal Travis CI
-configuration (see [here](#checking-style-on-a-ci-server)) and verify its status
-using another repository. The status of that repository's build is reported by
-the "travis example" badge above.
+**Note: this README is for _users_ rather than _contributors_.**
+If you wish to _contribute_ to the compiler, you should read
+[CONTRIBUTING.md](CONTRIBUTING.md) instead.
-## Quick start
+## Quick Start
-You can run `rustfmt` with Rust 1.24 and above.
+Read ["Installation"] from [The Book].
-### On the Stable toolchain
+["Installation"]: https://doc.rust-lang.org/book/ch01-01-installation.html
+[The Book]: https://doc.rust-lang.org/book/index.html
-To install:
+## Installing from Source
+
+The Rust build system uses a Python script called `x.py` to build the compiler,
+which manages the bootstrapping process. It lives at the root of the project.
+
+The `x.py` command can be run directly on most Unix systems in the following
+format:
```sh
-rustup component add rustfmt
+./x.py <subcommand> [flags]
```
-To run on a cargo project in the current working directory:
+This is how the documentation and examples assume you are running `x.py`.
+Some alternative ways are:
```sh
-cargo fmt
+# On a Unix shell if you don't have the necessary `python3` command
+./x <subcommand> [flags]
+
+# On the Windows Command Prompt (if .py files are configured to run Python)
+x.py <subcommand> [flags]
+
+# You can also run Python yourself, e.g.:
+python x.py <subcommand> [flags]
```
-### On the Nightly toolchain
+More information about `x.py` can be found by running it with the `--help` flag
+or reading the [rustc dev guide][rustcguidebuild].
-For the latest and greatest `rustfmt`, nightly is required.
+[gettingstarted]: https://rustc-dev-guide.rust-lang.org/getting-started.html
+[rustcguidebuild]: https://rustc-dev-guide.rust-lang.org/building/how-to-build-and-run.html
-To install:
+### Dependencies
-```sh
-rustup component add rustfmt --toolchain nightly
-```
+Make sure you have installed the dependencies:
-To run on a cargo project in the current working directory:
+* `python` 3 or 2.7
+* `git`
+* A C compiler (when building for the host, `cc` is enough; cross-compiling may
+ need additional compilers)
+* `curl` (not needed on Windows)
+* `pkg-config` if you are compiling on Linux and targeting Linux
+* `libiconv` (already included with glibc on Debian-based distros)
-```sh
-cargo +nightly fmt
-```
+To build Cargo, you'll also need OpenSSL (`libssl-dev` or `openssl-devel` on
+most Unix distros).
-## Limitations
+If building LLVM from source, you'll need additional tools:
-Rustfmt tries to work on as much Rust code as possible. Sometimes, the code
-doesn't even need to compile! In general, we are looking to limit areas of
-instability; in particular, post-1.0, the formatting of most code should not
-change as Rustfmt improves. However, there are some things that Rustfmt can't
-do or can't do well (and thus where formatting might change significantly,
-even post-1.0). We would like to reduce the list of limitations over time.
+* `g++`, `clang++`, or MSVC with versions listed on
+ [LLVM's documentation](https://llvm.org/docs/GettingStarted.html#host-c-toolchain-both-compiler-and-standard-library)
+* `ninja`, or GNU `make` 3.81 or later (Ninja is recommended, especially on
+ Windows)
+* `cmake` 3.13.4 or later
+* `libstdc++-static` may be required on some Linux distributions such as Fedora
+ and Ubuntu
-The following list enumerates areas where Rustfmt does not work or where the
-stability guarantees do not apply (we don't make a distinction between the two
-because in the future Rustfmt might work on code where it currently does not):
+On tier 1 or tier 2 with host tools platforms, you can also choose to download
+LLVM by setting `llvm.download-ci-llvm = true`.
+Otherwise, you'll need LLVM installed and `llvm-config` in your path.
+See [the rustc-dev-guide for more info][sysllvm].
-* a program where any part of the program does not parse (parsing is an early
- stage of compilation and in Rust includes macro expansion).
-* Macro declarations and uses (current status: some macro declarations and uses
- are formatted).
-* Comments, including any AST node with a comment 'inside' (Rustfmt does not
- currently attempt to format comments, it does format code with comments inside, but that formatting may change in the future).
-* Rust code in code blocks in comments.
-* Any fragment of a program (i.e., stability guarantees only apply to whole
- programs, even where fragments of a program can be formatted today).
-* Code containing non-ascii unicode characters (we believe Rustfmt mostly works
- here, but do not have the test coverage or experience to be 100% sure).
-* Bugs in Rustfmt (like any software, Rustfmt has bugs, we do not consider bug
- fixes to break our stability guarantees).
+[sysllvm]: https://rustc-dev-guide.rust-lang.org/building/new-target.html#using-pre-built-llvm
-## Installation
+### Building on a Unix-like system
-```sh
-rustup component add rustfmt
-```
+1. Clone the [source] with `git`:
-## Installing from source
+ ```sh
+ git clone https://github.com/rust-lang/rust.git
+ cd rust
+ ```
-To install from source (nightly required), first checkout to the tag or branch you want to install, then issue
+[source]: https://github.com/rust-lang/rust
-```sh
-cargo install --path .
+2. Configure the build settings:
+
+ The Rust build system uses a file named `config.toml` in the root of the
+ source tree to determine various configuration settings for the build.
+ Set up the defaults intended for distros to get started. You can see a full
+ list of options in `config.toml.example`.
+
+ ```sh
+ printf 'profile = "user" \nchangelog-seen = 2 \n' > config.toml
+ ```
+
+ If you plan to use `x.py install` to create an installation, it is
+ recommended that you set the `prefix` value in the `[install]` section to a
+ directory.
+
+3. Build and install:
+
+ ```sh
+ ./x.py build && ./x.py install
+ ```
+
+ When complete, `./x.py install` will place several programs into
+ `$PREFIX/bin`: `rustc`, the Rust compiler, and `rustdoc`, the
+ API-documentation tool. If you've set `profile = "user"` or
+ `build.extended = true`, it will also include [Cargo], Rust's package
+ manager.
+
+[Cargo]: https://github.com/rust-lang/cargo
+
+### Building on Windows
+
+On Windows, we suggest using [winget] to install dependencies by running the
+following in a terminal:
+
+```powershell
+winget install -e Python.Python.3
+winget install -e Kitware.CMake
+winget install -e Git.Git
```
-This will install `rustfmt` in your `~/.cargo/bin`. Make sure to add `~/.cargo/bin` directory to
-your PATH variable.
+Then edit your system's `PATH` variable and add: `C:\Program Files\CMake\bin`.
+See
+[this guide on editing the system `PATH`](https://www.java.com/en/download/help/path.html)
+from the Java documentation.
+[winget]: https://github.com/microsoft/winget-cli
-## Running
+There are two prominent ABIs in use on Windows: the native (MSVC) ABI used by
+Visual Studio and the GNU ABI used by the GCC toolchain. Which version of Rust
+you need depends largely on what C/C++ libraries you want to interoperate with.
+Use the MSVC build of Rust to interop with software produced by Visual Studio
+and the GNU build to interop with GNU software built using the MinGW/MSYS2
+toolchain.
-You can run Rustfmt by just typing `rustfmt filename` if you used `cargo
-install`. This runs rustfmt on the given file, if the file includes out of line
-modules, then we reformat those too. So to run on a whole module or crate, you
-just need to run on the root file (usually mod.rs or lib.rs). Rustfmt can also
-read data from stdin. Alternatively, you can use `cargo fmt` to format all
-binary and library targets of your crate.
+#### MinGW
-You can run `rustfmt --help` for information about available arguments.
-The easiest way to run rustfmt against a project is with `cargo fmt`. `cargo fmt` works on both
-single-crate projects and [cargo workspaces](https://doc.rust-lang.org/book/ch14-03-cargo-workspaces.html).
-Please see `cargo fmt --help` for usage information.
+[MSYS2][msys2] can be used to easily build Rust on Windows:
-You can specify the path to your own `rustfmt` binary for cargo to use by setting the`RUSTFMT`
-environment variable. This was added in v1.4.22, so you must have this version or newer to leverage this feature (`cargo fmt --version`)
+[msys2]: https://www.msys2.org/
-### Running `rustfmt` directly
+1. Download the latest [MSYS2 installer][msys2] and go through the installer.
-To format individual files or arbitrary codes from stdin, the `rustfmt` binary should be used. Some
-examples follow:
+2. Run `mingw32_shell.bat` or `mingw64_shell.bat` from the MSYS2 installation
+ directory (e.g. `C:\msys64`), depending on whether you want 32-bit or 64-bit
+ Rust. (As of the latest version of MSYS2 you have to run `msys2_shell.cmd
+ -mingw32` or `msys2_shell.cmd -mingw64` from the command line instead.)
-- `rustfmt lib.rs main.rs` will format "lib.rs" and "main.rs" in place
-- `rustfmt` will read a code from stdin and write formatting to stdout
- - `echo "fn main() {}" | rustfmt` would emit "fn main() {}".
+3. From this terminal, install the required tools:
-For more information, including arguments and emit options, see `rustfmt --help`.
+ ```sh
+ # Update package mirrors (may be needed if you have a fresh install of MSYS2)
+ pacman -Sy pacman-mirrors
-### Verifying code is formatted
+ # Install build tools needed for Rust. If you're building a 32-bit compiler,
+ # then replace "x86_64" below with "i686". If you've already got Git, Python,
+ # or CMake installed and in PATH you can remove them from this list.
+ # Note that it is important that you do **not** use the 'python2', 'cmake',
+ # and 'ninja' packages from the 'msys2' subsystem.
+ # The build has historically been known to fail with these packages.
+ pacman -S git \
+ make \
+ diffutils \
+ tar \
+ mingw-w64-x86_64-python \
+ mingw-w64-x86_64-cmake \
+ mingw-w64-x86_64-gcc \
+ mingw-w64-x86_64-ninja
+ ```
-When running with `--check`, Rustfmt will exit with `0` if Rustfmt would not
-make any formatting changes to the input, and `1` if Rustfmt would make changes.
-In other modes, Rustfmt will exit with `1` if there was some error during
-formatting (for example a parsing or internal error) and `0` if formatting
-completed without error (whether or not changes were made).
+4. Navigate to Rust's source code (or clone it), then build it:
+ ```sh
+ ./x.py build && ./x.py install
+ ```
+#### MSVC
-## Running Rustfmt from your editor
+MSVC builds of Rust additionally require an installation of Visual Studio 2017
+(or later) so `rustc` can use its linker. The simplest way is to get
+[Visual Studio], check the "C++ build tools" and "Windows 10 SDK" workload.
-* [Vim](https://github.com/rust-lang/rust.vim#formatting-with-rustfmt)
-* [Emacs](https://github.com/rust-lang/rust-mode)
-* [Sublime Text 3](https://packagecontrol.io/packages/RustFmt)
-* [Atom](atom.md)
-* [Visual Studio Code](https://marketplace.visualstudio.com/items?itemName=rust-lang.rust-analyzer)
-* [IntelliJ or CLion](intellij.md)
+[Visual Studio]: https://visualstudio.microsoft.com/downloads/
+(If you're installing CMake yourself, be careful that "C++ CMake tools for
+Windows" doesn't get included under "Individual components".)
-## Checking style on a CI server
+With these dependencies installed, you can build the compiler in a `cmd.exe`
+shell with:
-To keep your code base consistently formatted, it can be helpful to fail the CI build
-when a pull request contains unformatted code. Using `--check` instructs
-rustfmt to exit with an error code if the input is not formatted correctly.
-It will also print any found differences. (Older versions of Rustfmt don't
-support `--check`, use `--write-mode diff`).
+```sh
+python x.py build
+```
-A minimal Travis setup could look like this (requires Rust 1.31.0 or greater):
+Right now, building Rust only works with some known versions of Visual Studio.
+If you have a more recent version installed and the build system doesn't
+understand, you may need to force rustbuild to use an older version.
+This can be done by manually calling the appropriate vcvars file before running
+the bootstrap.
-```yaml
-language: rust
-before_script:
-- rustup component add rustfmt
-script:
-- cargo build
-- cargo test
-- cargo fmt --all -- --check
+```batch
+CALL "C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Auxiliary\Build\vcvars64.bat"
+python x.py build
```
-See [this blog post](https://medium.com/@ag_dubs/enforcing-style-in-ci-for-rust-projects-18f6b09ec69d)
-for more info.
+#### Specifying an ABI
-## How to build and test
+Each specific ABI can also be used from either environment (for example, using
+the GNU ABI in PowerShell) by using an explicit build triple. The available
+Windows build triples are:
+- GNU ABI (using GCC)
+ - `i686-pc-windows-gnu`
+ - `x86_64-pc-windows-gnu`
+- The MSVC ABI
+ - `i686-pc-windows-msvc`
+ - `x86_64-pc-windows-msvc`
-`cargo build` to build.
+The build triple can be specified by either specifying `--build=<triple>` when
+invoking `x.py` commands, or by creating a `config.toml` file (as described in
+[Installing from Source](#installing-from-source)), and modifying the `build`
+option under the `[build]` section.
-`cargo test` to run all tests.
+### Configure and Make
-To run rustfmt after this, use `cargo run --bin rustfmt -- filename`. See the
-notes above on running rustfmt.
+While it's not the recommended build system, this project also provides a
+configure script and makefile (the latter of which just invokes `x.py`).
+```sh
+./configure
+make && sudo make install
+```
-## Configuring Rustfmt
+`configure` generates a `config.toml` which can also be used with normal `x.py`
+invocations.
-Rustfmt is designed to be very configurable. You can create a TOML file called
-`rustfmt.toml` or `.rustfmt.toml`, place it in the project or any other parent
-directory and it will apply the options in that file. See `rustfmt
---help=config` for the options which are available, or if you prefer to see
-visual style previews, [GitHub page](https://rust-lang.github.io/rustfmt/).
+## Building Documentation
-By default, Rustfmt uses a style which conforms to the [Rust style guide][style
-guide] that has been formalized through the [style RFC
-process][fmt rfcs].
+If you'd like to build the documentation, it's almost the same:
-Configuration options are either stable or unstable. Stable options can always
-be used, while unstable ones are only available on a nightly toolchain, and opt-in.
-See [GitHub page](https://rust-lang.github.io/rustfmt/) for details.
+```sh
+./x.py doc
+```
-### Rust's Editions
+The generated documentation will appear under `doc` in the `build` directory for
+the ABI used. That is, if the ABI was `x86_64-pc-windows-msvc`, the directory
+will be `build\x86_64-pc-windows-msvc\doc`.
-Rustfmt is able to pick up the edition used by reading the `Cargo.toml` file if
-executed through the Cargo's formatting tool `cargo fmt`. Otherwise, the edition
-needs to be specified in `rustfmt.toml`, e.g., with `edition = "2018"`.
+## Notes
-## Tips
+Since the Rust compiler is written in Rust, it must be built by a precompiled
+"snapshot" version of itself (made in an earlier stage of development).
+As such, source builds require an Internet connection to fetch snapshots, and an
+OS that can execute the available snapshot binaries.
-* For things you do not want rustfmt to mangle, use `#[rustfmt::skip]`
-* To prevent rustfmt from formatting a macro or an attribute,
- use `#[rustfmt::skip::macros(target_macro_name)]` or
- `#[rustfmt::skip::attributes(target_attribute_name)]`
+See https://doc.rust-lang.org/nightly/rustc/platform-support.html for a list of
+supported platforms.
+Only "host tools" platforms have a pre-compiled snapshot binary available; to
+compile for a platform without host tools you must cross-compile.
- Example:
+You may find that other platforms work, but these are our officially supported
+build environments that are most likely to work.
- ```rust
- #![rustfmt::skip::attributes(custom_attribute)]
+## Getting Help
- #[custom_attribute(formatting , here , should , be , Skipped)]
- #[rustfmt::skip::macros(html)]
- fn main() {
- let macro_result1 = html! { <div>
- Hello</div>
- }.to_string();
- ```
-* When you run rustfmt, place a file named `rustfmt.toml` or `.rustfmt.toml` in
- target file directory or its parents to override the default settings of
- rustfmt. You can generate a file containing the default configuration with
- `rustfmt --print-config default rustfmt.toml` and customize as needed.
-* After successful compilation, a `rustfmt` executable can be found in the
- target directory.
-* If you're having issues compiling Rustfmt (or compile errors when trying to
- install), make sure you have the most recent version of Rust installed.
+See https://www.rust-lang.org/community for a list of chat platforms and forums.
-* You can change the way rustfmt emits the changes with the --emit flag:
+## Contributing
- Example:
+See [CONTRIBUTING.md](CONTRIBUTING.md).
- ```sh
- cargo fmt -- --emit files
- ```
+## License
- Options:
+Rust is primarily distributed under the terms of both the MIT license and the
+Apache License (Version 2.0), with portions covered by various BSD-like
+licenses.
- | Flag |Description| Nightly Only |
- |:---:|:---:|:---:|
- | files | overwrites output to files | No |
- | stdout | writes output to stdout | No |
- | coverage | displays how much of the input file was processed | Yes |
- | checkstyle | emits in a checkstyle format | Yes |
- | json | emits diffs in a json format | Yes |
+See [LICENSE-APACHE](LICENSE-APACHE), [LICENSE-MIT](LICENSE-MIT), and
+[COPYRIGHT](COPYRIGHT) for details.
-## License
+## Trademark
+
+[The Rust Foundation][rust-foundation] owns and protects the Rust and Cargo
+trademarks and logos (the "Rust Trademarks").
-Rustfmt is distributed under the terms of both the MIT license and the
-Apache License (Version 2.0).
+If you want to use these names or brands, please read the
+[media guide][media-guide].
-See [LICENSE-APACHE](LICENSE-APACHE) and [LICENSE-MIT](LICENSE-MIT) for details.
+Third-party logos may be subject to third-party copyrights and trademarks. See
+[Licenses][policies-licenses] for details.
-[rust]: https://github.com/rust-lang/rust
-[fmt rfcs]: https://github.com/rust-dev-tools/fmt-rfcs
-[style guide]: https://github.com/rust-dev-tools/fmt-rfcs/blob/master/guide/guide.md
+[rust-foundation]: https://foundation.rust-lang.org/
+[media-guide]: https://foundation.rust-lang.org/policies/logo-policy-and-media-guide/
+[policies-licenses]: https://www.rust-lang.org/policies/licenses
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