README.md - third_party/rust - Git at Google

 # The Rust Programming Language

 This is the main source code repository for [Rust]. It contains the compiler,
 standard library, and documentation.

 [Rust]: https://www.rust-lang.org

 **Note: this README is for _users_ rather than _contributors_.
 If you wish to _contribute_ to the compiler, you should read the
 [Getting Started][gettingstarted] section of the rustc-dev-guide instead.
 You can ask for help in the [#new members Zulip stream][new-members].**

 [new-members]: https://rust-lang.zulipchat.com/#narrow/stream/122652-new-members

 ## Quick Start

 Read ["Installation"] from [The Book].

 ["Installation"]: https://doc.rust-lang.org/book/ch01-01-installation.html
 [The Book]: https://doc.rust-lang.org/book/index.html

 ## 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 in the root of the project.

 The `x.py` command can be run directly on most systems in the following format:

 ```sh
 ./x.py <subcommand> [flags]
 ```

 This is how the documentation and examples assume you are running `x.py`.

 Systems such as Ubuntu 20.04 LTS do not create the necessary `python` command by default when Python is installed that allows `x.py` to be run directly. In that case you can either create a symlink for `python` (Ubuntu provides the `python-is-python3` package for this), or run `x.py` using Python itself:

 ```sh
 # Python 3
 python3 x.py <subcommand> [flags]

 # Python 2.7
 python2.7 x.py <subcommand> [flags]
 ```

 More information about `x.py` can be found
 by running it with the `--help` flag or reading the [rustc dev guide][rustcguidebuild].

 [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

 ### Building on a Unix-like system
 1. Make sure you have installed the dependencies:

    * `g++` 5.1 or later or `clang++` 3.5 or later
    * `python` 3 or 2.7
    * GNU `make` 3.81 or later
    * `cmake` 3.13.4 or later
    * `ninja`
    * `curl`
    * `git`
    * `ssl` which comes in `libssl-dev` or `openssl-devel`
    * `pkg-config` if you are compiling on Linux and targeting Linux

 2. Clone the [source] with `git`:

    ```sh
    git clone https://github.com/rust-lang/rust.git
    cd rust
    ```

 [source]: https://github.com/rust-lang/rust

 3. 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.
     Copy the default `config.toml.example` to `config.toml` to get started.

     ```sh
     cp config.toml.example 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.

     Create install directory if you are not installing in default directory

 4. 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. This install does not include [Cargo],
     Rust's package manager. To build and install Cargo, you may
     run `./x.py install cargo` or set the `build.extended` key in
     `config.toml` to `true` to build and install all tools.

 [Cargo]: https://github.com/rust-lang/cargo

 ### Building on Windows

 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:
 for interop with software produced by Visual Studio use the MSVC build of Rust;
 for interop with GNU software built using the MinGW/MSYS2 toolchain use the GNU
 build.

 #### MinGW

 [MSYS2][msys2] can be used to easily build Rust on Windows:

 [msys2]: https://www.msys2.org/

 1. Grab the latest [MSYS2 installer][msys2] and go through the installer.

 2. Run `mingw32_shell.bat` or `mingw64_shell.bat` from wherever you installed
    MSYS2 (i.e. `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)

 3. From this terminal, install the required tools:

    ```sh
    # Update package mirrors (may be needed if you have a fresh install of MSYS2)
    pacman -Sy pacman-mirrors

    # 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
    ```

 4. Navigate to Rust's source code (or clone it), then build it:

    ```sh
    ./x.py build && ./x.py install
    ```

 #### MSVC

 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 the
 [Visual Studio], check the “C++ build tools” and “Windows 10 SDK” workload.

 [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”.)

 With these dependencies installed, you can build the compiler in a `cmd.exe`
 shell with:

 ```sh
 python x.py build
 ```

 Currently, 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.

 ```batch
 CALL "C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Auxiliary\Build\vcvars64.bat"
 python x.py build
 ```

 #### Specifying an ABI

 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`

 The build triple can be specified by either specifying `--build=<triple>` when
 invoking `x.py` commands, or by copying the `config.toml` file (as described
 in [Installing From Source](#installing-from-source)), and modifying the
 `build` option under the `[build]` section.

 ### Configure and Make

 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
 ```

 When using the configure script, the generated `config.mk` file may override the
 `config.toml` file. To go back to the `config.toml` file, delete the generated
 `config.mk` file.

 ## Building Documentation

 If you’d like to build the documentation, it’s almost the same:

 ```sh
 ./x.py doc
 ```

 The generated documentation will appear under `doc` in the `build` directory for
 the ABI used. I.e., if the ABI was `x86_64-pc-windows-msvc`, the directory will be
 `build\x86_64-pc-windows-msvc\doc`.

 ## Notes

 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 a connection to the Internet, to
 fetch snapshots, and an OS that can execute the available snapshot binaries.

 Snapshot binaries are currently built and tested on several platforms:

 | Platform / Architecture                     | x86 | x86_64 |
 |---------------------------------------------|-----|--------|
 | Windows (7, 8, 10, ...)                     | ✓   | ✓      |
 | Linux (kernel 2.6.32, glibc 2.11 or later)  | ✓   | ✓      |
 | macOS (10.7 Lion or later)                  | (\*) | ✓      |

 (\*): Apple dropped support for running 32-bit binaries starting from macOS 10.15 and iOS 11.
 Due to this decision from Apple, the targets are no longer useful to our users.
 Please read [our blog post][macx32] for more info.

 [macx32]: https://blog.rust-lang.org/2020/01/03/reducing-support-for-32-bit-apple-targets.html

 You may find that other platforms work, but these are our officially
 supported build environments that are most likely to work.

 ## Getting Help

 The Rust community congregates in a few places:

 * [Stack Overflow] - Direct questions about using the language.
 * [users.rust-lang.org] - General discussion and broader questions.
 * [/r/rust] - News and general discussion.

 [Stack Overflow]: https://stackoverflow.com/questions/tagged/rust
 [/r/rust]: https://reddit.com/r/rust
 [users.rust-lang.org]: https://users.rust-lang.org/

 ## Contributing

 If you are interested in contributing to the Rust project, please take a look
 at the [Getting Started][gettingstarted] guide in the [rustc-dev-guide].

 [rustc-dev-guide]: https://rustc-dev-guide.rust-lang.org

 ## License

 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.

 See [LICENSE-APACHE](LICENSE-APACHE), [LICENSE-MIT](LICENSE-MIT), and
 [COPYRIGHT](COPYRIGHT) for details.

 ## Trademark

 [The Rust Foundation][rust-foundation] owns and protects the Rust and Cargo
 trademarks and logos (the “Rust Trademarks”).

 If you want to use these names or brands, please read the [media guide][media-guide].

 Third-party logos may be subject to third-party copyrights and trademarks. See
 [Licenses][policies-licenses] for details.

 [rust-foundation]: https://foundation.rust-lang.org/
 [media-guide]: https://www.rust-lang.org/policies/media-guide
 [policies-licenses]: https://www.rust-lang.org/policies/licenses
	# The Rust Programming Language

	This is the main source code repository for [Rust]. It contains the compiler,
	standard library, and documentation.

	[Rust]: https://www.rust-lang.org

	**Note: this README is for _users_ rather than _contributors_.
	If you wish to _contribute_ to the compiler, you should read the
	[Getting Started][gettingstarted] section of the rustc-dev-guide instead.
	You can ask for help in the [#new members Zulip stream][new-members].**

	[new-members]: https://rust-lang.zulipchat.com/#narrow/stream/122652-new-members

	## Quick Start

	Read ["Installation"] from [The Book].

	["Installation"]: https://doc.rust-lang.org/book/ch01-01-installation.html
	[The Book]: https://doc.rust-lang.org/book/index.html

	## 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 in the root of the project.

	The `x.py` command can be run directly on most systems in the following format:

	```sh
	./x.py <subcommand> [flags]
	```

	This is how the documentation and examples assume you are running `x.py`.

	Systems such as Ubuntu 20.04 LTS do not create the necessary `python` command by default when Python is installed that allows `x.py` to be run directly. In that case you can either create a symlink for `python` (Ubuntu provides the `python-is-python3` package for this), or run `x.py` using Python itself:

	```sh
	# Python 3
	python3 x.py <subcommand> [flags]

	# Python 2.7
	python2.7 x.py <subcommand> [flags]
	```

	More information about `x.py` can be found
	by running it with the `--help` flag or reading the [rustc dev guide][rustcguidebuild].

	[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

	### Building on a Unix-like system
	1. Make sure you have installed the dependencies:

	* `g++` 5.1 or later or `clang++` 3.5 or later
	* `python` 3 or 2.7
	* GNU `make` 3.81 or later
	* `cmake` 3.13.4 or later
	* `ninja`
	* `curl`
	* `git`
	* `ssl` which comes in `libssl-dev` or `openssl-devel`
	* `pkg-config` if you are compiling on Linux and targeting Linux

	2. Clone the [source] with `git`:

	```sh
	git clone https://github.com/rust-lang/rust.git
	cd rust
	```

	[source]: https://github.com/rust-lang/rust

	3. 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.
	Copy the default `config.toml.example` to `config.toml` to get started.

	```sh
	cp config.toml.example 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.

	Create install directory if you are not installing in default directory

	4. 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. This install does not include [Cargo],
	Rust's package manager. To build and install Cargo, you may
	run `./x.py install cargo` or set the `build.extended` key in
	`config.toml` to `true` to build and install all tools.

	[Cargo]: https://github.com/rust-lang/cargo

	### Building on Windows

	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:
	for interop with software produced by Visual Studio use the MSVC build of Rust;
	for interop with GNU software built using the MinGW/MSYS2 toolchain use the GNU
	build.

	#### MinGW

	[MSYS2][msys2] can be used to easily build Rust on Windows:

	[msys2]: https://www.msys2.org/

	1. Grab the latest [MSYS2 installer][msys2] and go through the installer.

	2. Run `mingw32_shell.bat` or `mingw64_shell.bat` from wherever you installed
	MSYS2 (i.e. `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)

	3. From this terminal, install the required tools:

	```sh
	# Update package mirrors (may be needed if you have a fresh install of MSYS2)
	pacman -Sy pacman-mirrors

	# 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
	```

	4. Navigate to Rust's source code (or clone it), then build it:

	```sh
	./x.py build && ./x.py install
	```

	#### MSVC

	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 the
	[Visual Studio], check the “C++ build tools” and “Windows 10 SDK” workload.

	[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”.)

	With these dependencies installed, you can build the compiler in a `cmd.exe`
	shell with:

	```sh
	python x.py build
	```

	Currently, 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.

	```batch
	CALL "C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Auxiliary\Build\vcvars64.bat"
	python x.py build
	```

	#### Specifying an ABI

	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`

	The build triple can be specified by either specifying `--build=<triple>` when
	invoking `x.py` commands, or by copying the `config.toml` file (as described
	in [Installing From Source](#installing-from-source)), and modifying the
	`build` option under the `[build]` section.

	### Configure and Make

	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
	```

	When using the configure script, the generated `config.mk` file may override the
	`config.toml` file. To go back to the `config.toml` file, delete the generated
	`config.mk` file.

	## Building Documentation

	If you’d like to build the documentation, it’s almost the same:

	```sh
	./x.py doc
	```

	The generated documentation will appear under `doc` in the `build` directory for
	the ABI used. I.e., if the ABI was `x86_64-pc-windows-msvc`, the directory will be
	`build\x86_64-pc-windows-msvc\doc`.

	## Notes

	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 a connection to the Internet, to
	fetch snapshots, and an OS that can execute the available snapshot binaries.

	Snapshot binaries are currently built and tested on several platforms:

	\| Platform / Architecture \| x86 \| x86_64 \|
	\|---------------------------------------------\|-----\|--------\|
	\| Windows (7, 8, 10, ...) \| ✓ \| ✓ \|
	\| Linux (kernel 2.6.32, glibc 2.11 or later) \| ✓ \| ✓ \|
	\| macOS (10.7 Lion or later) \| (\*) \| ✓ \|

	(\*): Apple dropped support for running 32-bit binaries starting from macOS 10.15 and iOS 11.
	Due to this decision from Apple, the targets are no longer useful to our users.
	Please read [our blog post][macx32] for more info.

	[macx32]: https://blog.rust-lang.org/2020/01/03/reducing-support-for-32-bit-apple-targets.html

	You may find that other platforms work, but these are our officially
	supported build environments that are most likely to work.

	## Getting Help

	The Rust community congregates in a few places:

	* [Stack Overflow] - Direct questions about using the language.
	* [users.rust-lang.org] - General discussion and broader questions.
	* [/r/rust] - News and general discussion.

	[Stack Overflow]: https://stackoverflow.com/questions/tagged/rust
	[/r/rust]: https://reddit.com/r/rust
	[users.rust-lang.org]: https://users.rust-lang.org/

	## Contributing

	If you are interested in contributing to the Rust project, please take a look
	at the [Getting Started][gettingstarted] guide in the [rustc-dev-guide].

	[rustc-dev-guide]: https://rustc-dev-guide.rust-lang.org

	## License

	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.

	See [LICENSE-APACHE](LICENSE-APACHE), [LICENSE-MIT](LICENSE-MIT), and
	[COPYRIGHT](COPYRIGHT) for details.

	## Trademark

	[The Rust Foundation][rust-foundation] owns and protects the Rust and Cargo
	trademarks and logos (the “Rust Trademarks”).

	If you want to use these names or brands, please read the [media guide][media-guide].

	Third-party logos may be subject to third-party copyrights and trademarks. See
	[Licenses][policies-licenses] for details.

	[rust-foundation]: https://foundation.rust-lang.org/
	[media-guide]: https://www.rust-lang.org/policies/media-guide
	[policies-licenses]: https://www.rust-lang.org/policies/licenses