Swift 5.0 Release Process

This post describes the goals, release process, and estimated schedule for Swift 5.0.

Motivation and Goals

The primary goal of Swift 5.0 is for the language to achieve ABI stability. This will enable a stable Swift runtime to be deployed by OS vendors that can be linked against by executables and libraries.

Related to ABI stability, module stability will be a primary focal point as well. This will land in either the Swift 5.0 release or in a subsequent 5.x release depending on its readiness.

Binary Compatibility

Swift 5.0 is not binary compatible with earlier Swift releases. Binary compatibility allows Swift code compiled by different Swift compilers to link together and interoperate at a runtime level.

However, future Swift releases will be binary compatible with Swift 5.

Source Compatibility

As with Swift 4.2, the vast majority of sources that built with the Swift 4.2 compiler should compile with the Swift 5.0 compiler.

However, the Swift 3 compatibility mode will not be supported in the Swift 5 compiler. Swift 4.2 is the last release of Swift to support Swift 3 mode. There are important changes to both the surface of the language and the interior of its implementation in the releases following Swift 3 that will be the basis of future (and lasting) source and binary stability.

Snapshots of Swift 5.0

Downloadable snapshots of the Swift 5.0 release branch will be posted regularly as part of continuous integration testing.

Once Swift 5.0 is released, the official final builds will also be posted in addition to the snapshots.

Getting Changes into Swift 5.0

The swift-5.0-branch contains the changes that will be released in Swift 5.0. The branch will be managed as follows:

Five notable exceptions to this plan are swift-package-manager, swift-llbuild, swift-corelibs-foundation, swift-corelibs-xctest, and swift-corelibs-libdispatch which will merge from master into swift-5.0-branch daily and whose final cutoff date for changes will extend beyond November 16 and will be announced later.

Project Cutoff date
swift November 20, 2018
swift-package-manager February 11, 2019
swift-llbuild February 11, 2019

Philosophy on Taking Changes into Swift 5.0

Impacted Repositories

The following repositories will have a swift-5.0-branch branch to track sources as part of Swift 5.0 release:

Release Managers

The overall management of the release will be overseen by the following individuals, who will announce when stricter control of change goes into effect for the Swift 5.0 release as the release converges:

Please feel free to post on the development forum or contact Ted Kremenek directly concerning any questions about the release management process.

Pull Requests for Release Branch

In order for a pull request to be considered for inclusion in the release branch after the final re-branch from master it must include the following information:

All change going into the swift-5.0-branch (outside changes being merged in automatically from master) must go through pull requests that are accepted by the corresponding release manager.