Precompile bridging header and compilation of any swift files that import that import my objective-c framework with modulemap runs every build

Question

Created Jun ’25

Replies 2

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I have a project which is set up like so

App.xcproject
   App target { Dependency on Bridges.framework }
Bridges.xcproject 
   Bridges.framework

Bridges.framework has a bunch of Objective-c++ headers that import c++ headers/frameworks etc. It has a modulemap that allows it to generate bridging headers for the App target which is Swift only.

I have noticed that every single build Planning Swift module App is run for 1 second, then Precompile bridging header is run for a moment, then every single swift file that imports Bridges recompiles regardless of if it had any edits taking about 2-3 seconds.

It feels like since nothing has changed inside of Bridges that this bridging header precompile should not be necessary every single run.

Bridges.framework is in General/Frameworks as "Do not embed"
Bridges is in build phases "Target dependencies" and "Link binary with libraries"

Is this just normal and I should let this slide or is there a way to avoid this?

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Answer 1

Developer Tools Engineer OP

Apple

Jun ’25

Accepted Answer

Thanks for the feedback. It will be good if you can file a feedback report with a reproducer so we can take a look.

This is some information that help you debug:

If nothing really changed in your framework, build system should not run Planning job and it should be null build.
You can add flag -driver-show-incremental to OTHER_SWIFT_FLAGS and you can see how swift driver reasons about incremental build in Planning job output
swift-driver today doesn't check if PCH file is up-to-date (yes, please file feedback report or file issue on swift-driver GitHub), but that shouldn't affect incremental build for the individual swift files
In your case, it might be helpful to write a module map that turns your bridging header and everything it includes into an appropriate module. Then you get better dependency tracking and sharing in this case.

1

Answer 2

Caleb K OP

Jun ’25

Sounds good! Will try and catch it.

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