I want to check the output of the preprocessor for some files. How can I view the preprocessor's output in Xcode?
You can choose the "Show the Assistant editor" view in the top right set of buttons in the toolbar.
Then, at the top of the right-hand editor you can click the little Related Files button and then either choose Preprocess or Assembly.
You can see an example of both the preprocessor output and generated assembly code all side-by-side here:
Xcode 4.1 features now "Preprocessor or Assembly Output". All be happy!
@whoKnows's excellent and concise answer applies to Xcode 6 users. The preprocessor menu seems to wander all over the place from one Xcode version to another.
To recap: XCode 6 users can view preprocessor output by pulling down this menu:
Product -> Perform Action -> Preprocess
as illustrated in the accompanying screenshot. I couldn't find this anywhere in the Xcode documentation.
(I hope this helps. I would have preferred to simply add a comment to @whoKnows's answer, but I don't have privileges for that yet.)
You can always just run the preprocessor on the files from the command line using the -E flag with llvm-gcc (this is what Xcode 4 uses as a replacement for GCC). Something like this:
llvm-gcc -E -o output.preprocess input.c
Then you can just open up the output file in a text editor.
<menubar> -> Product -> Perform action -> Preprocess <the name of your file>
I did not find any way too. Seems that "Preprocess" feature is missing in Xcode 4. I haven't read any document from apple, where they mentioned anything about this.
Following uri might help you: http://pilky.me/view/15
来源：https://stackoverflow.com/questions/5937031/xcode-preprocessor-output