There are definitely times when it's overused, and times when it could be factored out. However, when you're dealing with the low level stuff a compiler that targets multiple architectures has to, using preprocessor defines can make things less maddening. GCC targets architectures that have all sorts of weird quirks regarding register locations and visibility, memory models, etc, that need to be accounted for. Without those #ifdefs, the code could very well be uglier with redundant checks, even uglier if statements, etc.