How can I check in Xcode that dependencies of my project compiled properly and only once by build.

To check in Xcode that the dependencies of your project compiled properly and only once, you can utilize the concept of explicitly built modules, which was introduced in Xcode 16. This feature provides a more detailed breakdown of the build process, allowing you to see where time is being spent and to optimize your build.

Here are the steps you can follow:

1. Enable Explicitly Built Modules:

   • Go to your project in the project navigator.
   • Select build settings and type "explicitly built" in the filter box.
   • Set the "Explicitly Built Module" setting to "Yes".

2. Build Your Project:

   • Start a build. The build log will now contain tasks such as scandependencies and compile module, which provide a detailed breakdown of the build process.

3. Analyze the Build Log:

   • Look for multiple instances of the same module being built. This can indicate that different build settings are causing multiple variants of a module to be compiled.
   • Use the "Modules Report" in the build log to see the different variants of modules and their build settings.

4. Optimize Build Settings:

   • Check for inconsistent build settings across different targets that might cause multiple module variants.
   • Move common build settings to a higher level (e.g., project or workspace level) to ensure modules can be shared between source files as much as possible.

For more detailed information on explicitly built modules and optimizing your build, you can refer to the session Demystify explicitly built modules (11:28).