This is really nice, I just have one question, ( maybe I have overlooked it), where is the test-suite for gathering the data?´, as to which headerfiles are workable or not? Is there a configure script there? I mean, I am on Snow Leopard, and I have no trouble using unistd.h which is marked as flawed on the graph.
The whole row for `unistd.h` is green (except for MSVC, of course) -- why would you think it's flawed on OS X?
All I see that is that it is a survey, I wonder what kind of tests that are used to draw the conclusions. I also see for instances that the regexp.h file is absent for OS X Lion, which is reworked to work wide wide characters. But, the header files may fail in ways I don't know about, that is why I ask for the tests that makes up for the results.