The "problem" at this part in the text is that the headers still have to get parsed multiple times by the preprocessor. With his approach this would not be nece

The "problem" at this part in the text is that the headers still have to get parsed multiple times by the preprocessor. With his approach this would not be necessary. That said, I don't think that is that big of a problem compared to final compile time reduction. EDIT: Disregard that, the preprocessor remembers the states of include guards. So there is literally no point.[1] [1] https://gcc.gnu.org/onlinedocs/cpp/Once-Only-Headers.html https://gcc.gnu.org/onlinedocs/cpp/Once-Only-Headers.html