C++ syntax is the same accross all platforms (although some vendors add their own "extensions" to their compilers). It's all the classes and libraries that come with the platform that make them different, like MFC.

OSX is *I believe* using something called Objective-C, which is an object-oriented C language, more like C then C++. I'd bet there were ways to use C/C++ to interface these as opposed to using Objective-C.