Doxygen include graph

Question

I know there is a doxygen option, to show include graphs, like
a.cpp includes a.h and b.h
a.h includes c.h
c.h includes <unistd.h>

But unistd.h does also include <features.h> for example!
How can I add the includes from 'system' headers, like unistd.h or windows.h, into the include dependency graph from doxygen?

Answer 1

Though you can add the system header path to the INPUT variable as pmr suggests, I would make a case for not adding them to the include graph.

If you want to do this so that you can say "ah, unistd.h already includes features.h so I don't need to include it myself" then I would advise against it. It's an implementation detail: you shouldn't care about it because it may change in a future version. If you need something in (eg) features.h then you should always include it because you can't rely on it already being included by a different header.