Doxygen assumes your header files are guarded against multiple inclusion and are self-contained (i.e. can be placed at the top of a .c file without causing compilation problems). 

This is usually good programming practice. 

Your example does not adhere to these assumptions. It uses a header file as a poor man's template that is expanded differently based on the inclusion context. So this will not work with doxygen, and it is also not clear what output doxygen should produce in such case. 

I'll add a note about this limitation in the documentation.

Adding "documentation" keyword per comment #1.