Adventures in Building Swift: Where's The Toolchain?

Inspired by some starter tasks being posted by Swift contributors I figured I could take a stab at what it would take to contribute. I’ve been writing swift for a few years now so with battle scars and a couple language migrations under my belt this past weekend I set out to get started.

Step 1:

Follow the Getting Started guides and get swift building locally… Cloning all the modules into the default directory layout was easy enough. Theres a script for it. SwiftFoundation includes an Xcode workspace to make development feel a little more similar to usual Swift development. Opened it up and ⌘+R

Foundation/FoundationErrors.swift:10:48: Use of undeclared type ‘ErrorProtocol'
... and many more build errors


It paid to have kept up to date on Swift’s progress so I knew some renaming was going to happen with the new API Guidelines. Changing a few references of ErrorProtocol to ErrorType squelched some errors which clued me into what was happening. Foundation, SwiftPM, and XCTest had already migrated to the new Swift 3 style API but the latest tool chain 3/1/2016a at the time was still a Swift 2 Toolchain.

I struggled a bit finding some guidance that was newcomer friendly that explained how to build a whole updated Toolchain. Luckily while digging around the mailing lists I found a message referencing the following pull request. someone else was having slightly similar issues building Swift components.

Jumping off of the mailing list traffic I built my own Toolchain

# Ran from the parent directory of the development folder because swift build system defaults depend on a particular project layout
$ swift/utils/build-toolchain local.swift

Then copied (or linked) the new tool chain to proper directory

# working out of the parent directory of the swift project structure
$ ln -s /swift/Library/Developer/Toolchains/swift-LOCAL-2016-03-13-a.xctoolchain /Library/Developer/Toolchains/swift-LOCAL-2016-03-13-a.xctoolchain

Step 1: Part 2

Finally, again, following the normal getting started instructions I linked Xcode and the commandline tools to the new Toolchain. Reopened the SwiftFoundation project reverting my experiment and:

Ld /Users/me/Library/Developer/Xcode/DerivedData/Foundation-bwakzktqvoihjjaxueecpzitisux/Build/Products/Debug/SwiftFoundation.framework/Versions/A/SwiftFoundation normal x86_64 ...

Ld is the linker and that means we just successfully build SwiftFoundation under Swift


As of 3/15/2016 there is still no prebuilt Swift 3 Toolchain so hopefully this blog post saves someone else’s weekend. Some contributors have gone ahead and begin to post links to prebuilt Swift 3 Toolchains, but building your own does not take terribly long.

Written by Aaron C. on 16 March 2016