Some time ago I mentioned a handy guide (way back in the iOS 4 days!) for using macros to accomodate users on different iOS versions.
Here’s a nice guide from Erica Sadun that provides a number of useful compiler directives customize the warnings and errors from Xcode’s clang compiler.
Among the tips you’ll find:
– How to use a supplied build script allowing you to convert comments to warnings (great for todo/fixme)
– Using a compatibility alias to create Mac or iOS specific code
– Creating custom compiler warnings
– Creating custom compiler errors
– Disabling specific warnings
You can find guide over on the Informit site.
A nice guide to some little known but useful compiler directive tricks.