One of the things I discovered while investigating building my own programming language was the fact that clang is much more then your typical front end to the llvm compiler. It turns out that clang can do all kinds of useful things for you if you’re trying to build your own C/C++/Objective-C IDE. Closer inspection of clang reveals that it can do all kinds of wonderful things like code completion, pointing to specific lines where you have coding mistakes, and much more. It’s a fantastic treasure trove of tools.
If you’re interested in learning more I would highly recommend taking a look at Doug Gregor’s LLVM Developer Meeting presentation titled “libclang: Thinking Beyond the Compiler” (slides/video) It’s a great presentation and it will get you on your way to building your own IDE or at least giving it some serious thought.