In Xcode What does it mean when a linked static library turns red when switching build configurations?

Question

I think the title is pretty clear. I have ran into this twice now.

The first time it indicated a problem, and my project wouldn't compile. The second time everything still worked.

Is it just a fluke if my code still builds when this turns red?

Answer 1

Anything in the files and groups list that turns red indicates a missing file or directory. This is not necessarily cause for concern, because in many instances the file is expected to be built as part of your build process.

In the case of your linked static library, you are probably depending on a second target or project to build the static library. When you changed build configurations, Xcode noticed that it had not yet been built, so it shows it as red. When you built the project and the dependent library was itself built, it turned black again.

Answer 2

The first time it indicated a problem, and my project wouldn't compile. The second time everything still worked.

That suggests that you don't have your build dependencies set up correctly, which will bite you every time you do a clean build. You need to make the target(s) that need the static library have an explicit build dependency on the target that builds that library.