I'm not very good at C any more, but I do have a project i need to compile on OSX. I'm using XCode4, and have the thing compiling fine in Linux, with gcc. The project uses a third party library, and that library is complaining that i'm not using C++, evidently. Here's the error it's throwing. #ifndef __cplusplus # error Must use C++ to compile this module! #endif It's also erroring on some C++ specific terms, such as 'class'. The file has a .hpp extension. I created the project as a C++ project. Can anyone point me in the right direction?