behind the scenes of the xcode build process
Asked on 06/17/2025
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The behind-the-scenes of the Xcode build process, particularly with the introduction of explicitly built modules, was discussed in several sessions at WWDC. In Xcode 16, the build process was enhanced by splitting the compilation of each source file into three distinct phases: scanning, building modules, and finally building the original code. This change allows for better parallelism, clearer error messages, and improved build efficiency.
Explicitly built modules are now surfaced in the build log, providing a detailed breakdown of the build process. This helps in optimizing builds by making it easier to see where time is being spent. The build timeline now includes explicit scan tasks, module compile tasks, and the original source file tasks, which take significantly less time due to this optimization.
For more detailed insights, you can refer to the session Demystify explicitly built modules (05:55) which explains how Xcode coordinates with compilers to discover and build modules, improving build efficiency and reliability.
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Demystify explicitly built modules
Explore how builds are changing in Xcode 16 with explicitly built modules. Discover how modules are used to build your code, how explicitly built modules improve transparency in compilation tasks, and how you can optimize your build by sharing modules across targets.