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swift

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apple /swift

The Swift Programming Language

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Swift Programming Language

| | Architecture | Master | Package | |---|:---:|:---:|:---:| | macOS | x86_64 |Build Status|Build Status| | Ubuntu 16.04 | x86_64 | Build Status|Build Status| | Ubuntu 18.04 | x86_64 | Build Status|Build Status| | Ubuntu 20.04 | x86_64 | Build Status|Build Status| | CentOS 8 | x86_64 | Build Status|Build Status| | Amazon Linux 2 | x86_64 | Build Status|Build Status|

Swift Community-Hosted CI Platforms

| OS | Architecture | Build | |---|:---:|:---:| |Ubuntu 16.04 | PPC64LE |Build Status| |Ubuntu 16.04 | AArch64 |Build Status| |Ubuntu 18.04 | AArch64 |Build Status| |Android | ARMv7 |Build Status| |Android | AArch64 |Build Status| |Windows 2019 (VS 2017) | x86_64 | Build Status| |Windows 2019 (VS 2019) | x86_64 | Build Status|

Swift TensorFlow Community-Hosted CI Platforms

| OS | Architecture | Build | |---|:---:|:---:| |Ubuntu 16.04 | x86_64 |Build Status| |macOS 10.13 | x86_64 |Build Status| |Ubuntu 16.04 (GPU) | x86_64 |Build Status|

Welcome to Swift

Swift is a high-performance system programming language. It has a clean and modern syntax, offers seamless access to existing C and Objective-C code and frameworks, and is memory safe by default.

Although inspired by Objective-C and many other languages, Swift is not itself a C-derived language. As a complete and independent language, Swift packages core features like flow control, data structures, and functions, with high-level constructs like objects, protocols, closures, and generics. Swift embraces modules, eliminating the need for headers and the code duplication they entail.

To learn more about the programming language, visit swift.org.

Contributing to Swift

Contributions to Swift are welcomed and encouraged! Please see theContributing to Swift guide.

To be a truly great community, Swift.org needs to welcome developers from all walks of life, with different backgrounds, and with a wide range of experience. A diverse and friendly community will have more great ideas, more unique perspectives, and produce more great code. We will work diligently to make the Swift community welcoming to everyone.

To give clarity of what is expected of our members, Swift has adopted the code of conduct defined by the Contributor Covenant. This document is used across many open source communities, and we think it articulates our values well. For more, see the Code of Conduct.

Getting Started

These instructions give the most direct path to a working Swift development environment. To build from source you will need about 2 GB of disk space for the source code and up to 70 GB of disk space for the build artifacts with full debugging. Depending on your machine, a clean build can take a few minutes to several hours. Naturally, incremental builds are much faster.

Once you are able to build things successfully and have a compile-test-debug loop going, check out the development tips for better productivity while working on the compiler.

You can also skim docs/README.md to understand what high-level documentation is available.

System Requirements

macOS, Ubuntu Linux LTS, and the latest Ubuntu Linux release are currently supported as host development operating systems.

Please make sure you use Python 2.x. Python 3.x is not supported currently.

macOS

To build for macOS, you need Xcode 12 beta. The required version of Xcode changes frequently, and is often a beta release. Check this document or the host information on https://ci.swift.org for the current required version.

You will also need CMake and Ninja, which can be installed via a package manager:

Homebrew

brew install cmake ninja

You can also use homebrew-bundlefrom the root of this repository's working directory to install all of these dependencies:

brew bundle

MacPorts

sudo port install cmake ninja

Instructions for installing CMake and Ninja directly can be found below.

Linux

For Ubuntu, you'll need the following development dependencies:

sudo apt-get install \ clang \ cmake \ git \ icu-devtools \ libcurl4-openssl-dev \ libedit-dev \ libicu-dev \ libncurses5-dev \ libpython-dev \ libsqlite3-dev \ libxml2-dev \ ninja-build \ pkg-config \ python \ python-six \ rsync \ swig \ systemtap-sdt-dev \ tzdata \ uuid-dev

Note: LLDB currently requires at least

swig-1.3.40

but will successfully build with version 2 shipped with Ubuntu.

Note: For Ubuntu 20.04, use

libpython2-dev

in place of the libpython-dev package above.

Getting Sources for Swift and Related Projects

First create a directory for all of the Swift sources:

mkdir swift-source cd swift-source

Note: This is important since update-checkout (see below) checks out repositories next to the Swift source directory. This means that if one clones Swift and has other unrelated repositories, update-checkout may not clone those repositories and will update them instead. Be aware that

update-checkout

currently does not support paths with non-ASCII characters. If such characters are present in the path to

swift-source

,

update-checkout

will fail.

Via HTTPS For those checking out sources as read-only, HTTPS works best:

git clone https://github.com/apple/swift.git ./swift/utils/update-checkout --clone

Via SSH For those who plan on regularly making direct commits, cloning over SSH may provide a better experience (which requiresuploading SSH keys to GitHub):

git clone [email protected]:apple/swift.git ./swift/utils/update-checkout --clone-with-ssh

Building Swift

The

build-script

is a high-level build automation script that supports basic options such as building a Swift-compatible LLDB, building the Swift Package Manager, building for various platforms, running tests after builds, and more.

There are two primary build systems to use: Xcode and Ninja. The Xcode build system allows you to work in Xcode, but Ninja is a bit faster and supports more environments.

First, make sure that you're in the swift directory:

cd swift

To build using Ninja, run:

utils/build-script --release-debuginfo

When developing Swift, it helps to build what you're working on in a debug configuration while building the rest of the project with optimizations. Below are some examples of using debug variants:

utils/build-script --release-debuginfo --debug-swift # Swift frontend built in debug utils/build-script --release-debuginfo --debug-swift-stdlib # Standard library built in debug utils/build-script --release-debuginfo --debug-swift --force-optimized-typechecker # Swift frontend sans type checker built in debug

Limiting the amount of debug code in the compiler has a very large impact on Swift compile times, and in turn the test execution time. If you want to build the entire project in debug, you can run:

utils/build-script --debug

For documentation of all available arguments, as well as additional usage information, see the inline help:

utils/build-script -h

Xcode

To build using Xcode, specify the

--xcode

argument on any of the above commands. Xcode can be used to edit the Swift source code, but it is not currently fully supported as a build environment for SDKs other than macOS. The generated Xcode project does not integrate with the test runner, but the tests can be run with the 'check-swift' target.

Build Products

All of the build products are placed in

swift-source/build/${TOOL}-${MODE}/${PRODUCT}-${PLATFORM}/

. If macOS Swift with Ninja in DebugAssert mode was built, all of the products would be in

swift-source/build/Ninja-DebugAssert/swift-macosx-x86\_64/

. It helps to save this directory as an environment variable for future use.

export SWIFT\_BUILD\_DIR="~/swift-source/build/Ninja-DebugAssert/swift-macosx-x86\_64"

Ninja

Once the first build has completed, Ninja can perform fast incremental builds of various products. These incremental builds are a big timesaver when developing and debugging.

cd ${SWIFT\_BUILD\_DIR} ninja swift-frontend

This will build the Swift compiler, but will not rebuild the standard library or any other target. Building the

swift-stdlib

target as an additional layer of testing from time to time is also a good idea. To build just the standard library, run:

ninja swift-stdlib

It is always a good idea to do a full build after using

update-checkout

.

Using Xcode

To open the Swift project in Xcode, open

${SWIFT\_BUILD\_DIR}/Swift.xcodeproj

. It will auto-create a lot of schemes for all of the available targets. A common debug flow would involve:

  • Select the 'swift-frontend' scheme.
  • Pull up the scheme editor (⌘⇧<).
  • Select the 'Arguments' tab and click the '+'.
  • Add the command line options.
  • Close the scheme editor.
  • Build and run.

Another option is to change the scheme to "Wait for executable to be launched", then run the build product in Terminal.

Swift Toolchains

Building

Swift toolchains are created using the scriptbuild-toolchain. This script is used by swift.org's CI to produce snapshots and can allow for one to locally reproduce such builds for development or distribution purposes. A typical invocation looks like the following:

$ ./swift/utils/build-toolchain $BUNDLE\_PREFIX

where

$BUNDLE\_PREFIX

is a string that will be prepended to the build date to give the bundle identifier of the toolchain's

Info.plist

. For instance, if

$BUNDLE\_PREFIX

was

com.example

, the toolchain produced will have the bundle identifier

com.example.YYYYMMDD

. It will be created in the directory you run the script with a filename of the form:

swift-LOCAL-YYYY-MM-DD-a-osx.tar.gz

.

Beyond building the toolchain,

build-toolchain

also supports the following (non-exhaustive) set of useful options::

--dry-run

: Perform a dry run build. This is off by default.

--test

: Test the toolchain after it has been compiled. This is off by default.

--distcc

: Use distcc to speed up the build by distributing the c++ part of the swift build. This is off by default.

More options may be added over time. Please pass

--help

to

build-toolchain

to see the full set of options.

Installing into Xcode

On macOS if one wants to install such a toolchain into Xcode:

  1. Untar and copy the toolchain to one of
    /Library/Developer/Toolchains/
    or
    ~/Library/Developer/Toolchains/
    . E.x.:
$ sudo tar -xzf swift-LOCAL-YYYY-MM-DD-a-osx.tar.gz -C / $ tar -xzf swift-LOCAL-YYYY-MM-DD-a-osx.tar.gz -C ~/

The script also generates an archive containing debug symbols which can be installed over the main archive allowing symbolication of any compiler crashes.

$ sudo tar -xzf swift-LOCAL-YYYY-MM-DD-a-osx-symbols.tar.gz -C / $ tar -xzf swift-LOCAL-YYYY-MM-DD-a-osx-symbols.tar.gz -C ~/
  1. Specify the local toolchain for Xcode's use via
    Xcode-\>Toolchains
    .

Build Failures

Make sure you are using the correct release of Xcode.

If you have changed Xcode versions but still encounter errors that appear to be related to the Xcode version, try passing

--clean

to

build-script

.

When a new version of Xcode is released, you can update your build without recompiling the entire project by passing the

--reconfigure

option.

Make sure all repositories are up to date with the

update-checkout

command described above.

Testing Swift

See docs/Testing.md, in particular the section on lit.py.

Learning More

Be sure to look through the docsdirectory for more information about the compiler. In particular, the documents titled Debugging the Swift Compiler andContinuous Integration for Swift are very helpful to understand before submitting your first PR.

Building Documentation

To read the compiler documentation, start by installing theSphinx documentation generator tool by running the command:

easy\_install -U "Sphinx \< 2.0"

Once complete, you can build the Swift documentation by changing directory intodocs and typing

make

. This compiles the

.rst

files in the docsdirectory into HTML in the

docs/\_build/html

directory.

Many of the docs are out of date, but you can see some historical design documents in the

docs

directory.

Another source of documentation is the standard library itself, located in

stdlib

. Much of the language is actually implemented in the library (including

Int

), and the standard library gives some examples of what can be expressed today.

Build Dependencies

CMake

CMake is the core infrastructure used to configure builds of Swift and its companion projects; at least version 3.16.5 is required.

On macOS, you can download the CMake Binary Distribution, bundled as an application, copy it to

/Applications

, and add the embedded command line tools to your

PATH

:

export PATH=/Applications/CMake.app/Contents/bin:$PATH

On Linux, if you have not already installed Swift's development dependencies, you can download and install the CMake package separately using the following command:

sudo apt-get install cmake

Ninja

Ninja is the current recommended build system for building Swift and is the default configuration generated by CMake. Pre-built packagesare available for macOS and Linux distributions. You can also clone Ninja next to the other projects and it will be bootstrapped automatically:

Via HTTPS

git clone https://github.com/ninja-build/ninja.git && cd ninja git checkout release cat README

Via SSH

git clone [email protected]:ninja-build/ninja.git && cd ninja git checkout release cat README

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