Merging upstream version 1.68.2+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 130 insertions, 111 deletions

diff --git a/README.md b/README.md
index 27e7145c5..0eb7c4b26 100644
--- a/README.md
+++ b/README.md
@@ -3,14 +3,11 @@
 This is the main source code repository for [Rust]. It contains the compiler,
 standard library, and documentation.
 
-[Rust]: https://www.rust-lang.org
+[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
+**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
 
@@ -24,44 +21,69 @@ Read ["Installation"] from [The Book].
 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 systems in the following format:
+The `x.py` command can be run directly on most Unix 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:
+Some alternative ways are:
 
 ```sh
-# Python 3
-python3 x.py <subcommand> [flags]
+# On a Unix shell if you don't have the necessary `python3` command
+./x <subcommand> [flags]
 
-# Python 2.7
-python2.7 x.py <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]
 ```
 
-More information about `x.py` can be found
-by running it with the `--help` flag or reading the [rustc dev guide][rustcguidebuild].
+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:
+### Dependencies
+
+Make sure you have installed the dependencies:
+
+* `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)
+
+To build Cargo, you'll also need OpenSSL (`libssl-dev` or `openssl-devel` on
+most Unix distros).
+
+If building LLVM from source, you'll need additional tools:
 
-   * `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
+* `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
 
-2. Clone the [source] with `git`:
+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].
+
+[sysllvm]: https://rustc-dev-guide.rust-lang.org/building/new-target.html#using-pre-built-llvm
+
+
+### Building on a Unix-like system
+
+1. Clone the [source] with `git`:
 
    ```sh
    git clone https://github.com/rust-lang/rust.git
@@ -70,43 +92,59 @@ by running it with the `--help` flag or reading the [rustc dev guide][rustcguide
 
 [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.
+2. Configure the build settings:
 
-    ```sh
-    cp config.toml.example config.toml
-    ```
+   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`.
 
-    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.
+   ```sh
+   printf 'profile = "user" \nchangelog-seen = 2 \n' > config.toml
+   ```
 
-    Create an install directory if you are not installing in the default directory.
+   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.
 
-4. Build and install:
+3. Build and install:
 
-    ```sh
-    ./x.py build && ./x.py install
-    ```
+   ```sh
+   ./x.py build && ./x.py install
+   ```
 
-    When complete, `./x.py install` will place several programs into
-    `$PREFIX/bin`: `rustc`, the Rust compiler, and `rustdoc`, the
-    API-documentation tool. This install does not include [Cargo],
-    Rust's package manager. To build and install Cargo, you may
-    run `./x.py install cargo` or set the `build.extended` key in
-    `config.toml` to `true` to build and install all tools.
+   When complete, `./x.py install` will place several programs into
+   `$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
+```
+
+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
+
 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.
+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.
 
 #### MinGW
 
@@ -119,7 +157,7 @@ the GNU build to interop with GNU software built using the MinGW/MSYS2 toolchain
 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)
+   -mingw32` or `msys2_shell.cmd -mingw64` from the command line instead.)
 
 3. From this terminal, install the required tools:
 
@@ -128,11 +166,11 @@ the GNU build to interop with GNU software built using the MinGW/MSYS2 toolchain
    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.
+   # 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 \
@@ -153,12 +191,12 @@ the GNU build to interop with GNU software built using the MinGW/MSYS2 toolchain
 
 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.
+[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”.)
+(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:
@@ -167,10 +205,11 @@ shell with:
 python x.py build
 ```
 
-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.
+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.
 
 ```batch
 CALL "C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Auxiliary\Build\vcvars64.bat"
@@ -190,9 +229,9 @@ Windows build triples are:
     - `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.
+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.
 
 ### Configure and Make
 
@@ -204,70 +243,49 @@ configure script and makefile (the latter of which just invokes `x.py`).
 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.
+`configure` generates a `config.toml` which can also be used with normal `x.py`
+invocations.
 
 ## Building Documentation
 
-If you’d like to build the documentation, it’s almost the same:
+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`.
+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`.
 
 ## 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 an Internet connection 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 3.2, glibc 2.17 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.
+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.
 
-[macx32]: https://blog.rust-lang.org/2020/01/03/reducing-support-for-32-bit-apple-targets.html
+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.
 
-You may find that other platforms work, but these are our officially
-supported build environments that are most likely to work.
+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/
+See https://www.rust-lang.org/community for a list of chat platforms and forums.
 
 ## 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
+See [CONTRIBUTING.md](CONTRIBUTING.md).
 
 ## 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.
+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.
@@ -275,13 +293,14 @@ See [LICENSE-APACHE](LICENSE-APACHE), [LICENSE-MIT](LICENSE-MIT), and
 ## Trademark
 
 [The Rust Foundation][rust-foundation] owns and protects the Rust and Cargo
-trademarks and logos (the “Rust Trademarks”).
+trademarks and logos (the "Rust Trademarks").
 
-If you want to use these names or brands, please read the [media guide][media-guide].
+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
+[media-guide]: https://foundation.rust-lang.org/policies/logo-policy-and-media-guide/
 [policies-licenses]: https://www.rust-lang.org/policies/licenses