To be fair here, NASA does say to avoid nesting headers. But then it follows up with this ridiculous statement: In extreme cases, where a large number of hea

To be fair here, NASA does say to avoid nesting headers. But then it follows up with this ridiculous statement: In extreme cases, where a large number of header files are to be included in several different source files, it is acceptable to put all common #includes in one include file. I would not trust anything else the author of that guide writes. EMBOSS says not to nest. The Atacama code suggests not nesting but then says: To avoid nested includes, use #define wrappers as follows: The last pdf states: This prevents including the same item more than once when a .c file includes several .h files (we rejected alternatives involving conditional compilation as too complicated). I guess it boils down to preference since the language allows you to do either, I just don't put a lot of stock in these style guides.