Question

I have been able to Archive on Xcode 4 successfully, but all of a sudden (??), I can’t. The build fails with an invalid .pch file. The error is pasted in below (got from a reattempt with -Winvalid-pch, but what seems to be happening from the build log is that the precompiled header is not actually getting precompiled– it’s an iOS app, and goes straight from a CopyPNG step to a .m compile.

Could I have flipped something by accident? Nothing seems odd in my diff of the .pbxproj file.

cc1obj: warning: /Users/myname/Library/Developer/Xcode/DerivedData/Foo-afikuaovoaeqhreaaaakpafseuuv/Build/PrecompiledHeaders/Foo_Prefix-guqixmujoiaaaacwjctfkrztxmbz/Foo_Prefix.pch.gch: created by a different GCC executable
cc1obj: error: /Users/myname/Library/Developer/Xcode/DerivedData/Foo-afikuaovoaeqhreaaaakpafseuuv/Build/PrecompiledHeaders/Foo_Prefix-guqixmujoiaaaacwjctfkrztxmbz/Foo_Prefix.pch: No such file or directory
cc1obj: error: one or more PCH files were found, but they were invalid

The “Precompile Prefix Header” build setting is “Yes” for all configurations. Product->Clean doesn’t help. Deleting the cached pch stuff under derived data doesn’t fix it. Really seems like the whole “precompile” step is missing.

Another factoid: Enabling the setting “Increase Sharing of Precompiled Headers” DOES let it succeed. But I can find almost no reference to what this flag really does, and I have never used it before. And perhaps reasonably, the precompile step still doesn’t show up when this happens.

Answer 1

Have you cleaned and then rebuilt? Product Menu ==> Clean. Cleaning usually solves such problems, effectively instructing Xcode to compile everything, regardless of whether it thinks the previous build of that file is still valid.

If that fails, try wiping out the Derived Data folder for the project, at ~/Library/Developer/Xcode/DerivedData/YourProjectNamexxx where xxx is a uuid-style string.