what's new in build system
Asked on 06/16/2025
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In the recent WWDC sessions, several updates were introduced to the build system, particularly focusing on explicitly built modules. Here are the key highlights:
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Explicitly Built Modules: This feature provides improved parallelism, better diagnostics, and faster debugging. Explicit modules are enabled by default for C and Objective-C code, and for Swift, you need to opt in. This change allows the build system to have better control over module build tasks, optimizing the build pipeline and improving build efficiency and reliability. The build process is split into three phases: scanning, building modules, and building the original source code. This separation allows for more precise and deterministic sharing of modules.
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Swift Build: Apple has open-sourced Swift Build, a powerful and extensible build engine used by Xcode and Swift Playground. It is being incorporated into the Swift Package Manager to unify the build experience across Swift Open Source Toolchains and Xcode. This new implementation supports all platforms in the Swift ecosystem, including Linux, Windows, and Android.
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Build System Improvements: The build system now makes more informed scheduling choices, avoiding execution lanes being blocked by compilation tasks waiting for a module to be built. This results in more efficient builds and faster debugging, as the debugger can reuse already built modules.
For more detailed insights, you can refer to the session Demystify explicitly built modules (08:37) which covers the module build log and optimizations. Additionally, the session What’s new in Xcode (27:50) discusses the builds in Xcode.
What’s new in Xcode
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What’s new in Xcode 16
Discover the latest productivity and performance improvements in Xcode 16. Learn about enhancements to code completion, diagnostics, and Xcode Previews. Find out more about updates in builds and explore improvements in debugging and Instruments.
What’s new in Swift
Join us for an update on Swift. We’ll talk about workflow improvements that make you more productive, and new and modernized library APIs for fundamental programming tasks. We’ll show examples of Swift adoption throughout more layers of the software stack. Finally, we’ll explore new language features for both improving approachability of concurrency, and achieving peak performance when you need it.