API Diff is a program that I wrote to let you compare two different versions of an API. The aim was to provide a tool that would simplify API reviews and to document everything that changed in a new version of your API.
It uses a C++ parser to provide specific support for C and C++ APIs, but can also handle other languages via a plain-text diff engine. It also lets you view all comment changes so that you can review any new documentation. You can view changes in a side-by-side visual format and generate a report on everything that changed. The program is available for free for Windows, Mac OS X, and Linux, with additional functionality available for a small license fee. For more details, see: