#cmakedefine can be used in C/C++ files instead of #define if you use the CMake build system (which is standard for KDE applications). When calling CMake, it will not only create the makefiles, but replace each occurence of #cmakedefine by either #define (if a variable of the same name lives in the build system) or comment it out (if there doens't live a variable of the same name in the build system).

Actually, I can't produce documentation for #cmakedefine. (I've tried it using "\def", but that results in an error message that no corresponding define is found, and my documentation isn't included in doxygens's output.) It would be great if doxygen could support #cmakedefine directives. They could be handeled exactly the same way like normal #define directives are handeld.