Swift Programming Language

Cross-Compilation Targets

Swift Community-Hosted CI Platforms

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 the
Contributing to Swift guide.

Before submitting the pull request, please make sure you have tested your
changes
and that they follow the Swift project guidelines for contributing
code.

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

If you are interested in:

• Contributing fixes and features to the compiler: See our
  How to Submit Your First Pull Request guide.
• Building the compiler as a one-off: See our Getting Started guide.
• Building a toolchain as a one-off: Follow the Getting Started guide
  up until the "Building the project" section. After that, follow the
  instructions in the Swift Toolchains section below.

We also have an FAQ that answers common questions.

Swift Toolchains

Building

Swift toolchains are created using the script
build-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:

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.
• --sccache: Use sccache to speed up subsequent builds of the compiler by
  caching more C++ build artifacts. 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.g.:

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

2. Specify the local toolchain for Xcode's use via Xcode->Toolchains.

Build Failures

Try the suggestions in
Troubleshooting build issues.

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 --reconfigure to build-script.

Learning More

Be sure to look at the documentation index for a bird's eye
view of the available documentation. In particular, the documents titled
Debugging the Swift Compiler and
Continuous Integration for Swift are very
helpful to understand before submitting your first PR.