Xcode -- get more info on why it chooses to include a file in the build?

I have a project that sits at the top of a complicated tree of other projects. The build involves the processing of multiple config files whi开发者_高级运维ch include other config files, and so on down the tree.

My project is compiling my top-level prefix header three times, and I have no idea why. I can look at the build log, and I see three entries that read "compile foo.pch". But I can't tell why this is happening. It compiles it with slightly different settings each time, and if I make a certain change to my project, two of the three attempts to compile foo.pch fail. Is there any way to break down whatever process Xcode uses to decide what to build in what order, in order to figure out why that is happening?

EDIT: Xcode 4.0.2. Architecture at the top level is only arm7, but some sub-projects have more architectures.

The answer is that it is compiling it once for straight C, once for objective C, and once for objective C++. See here.