Solid deep dive here. The section on header guards makes clear why duplicate inclusion bugs can be so confusing when you don't understand the preprocessor's textual expansion model. I ran into this exact issue last year tracking down redefinition errors, and the guard pattern wasn'tobvious until I understood that the preprocessor literally just copy-pastes file contents in place.
Thanks for reading! I really wanted that copy paste mental picture of the preprocessor to come through, so I’m glad the header guard section clicked with what you saw while chasing those redefinition errors. Making this article pushed me to go further into how that expansion step behaves, so I really appreciate the feedback and you sharing that debugging story!
Solid deep dive here. The section on header guards makes clear why duplicate inclusion bugs can be so confusing when you don't understand the preprocessor's textual expansion model. I ran into this exact issue last year tracking down redefinition errors, and the guard pattern wasn'tobvious until I understood that the preprocessor literally just copy-pastes file contents in place.
Thanks for reading! I really wanted that copy paste mental picture of the preprocessor to come through, so I’m glad the header guard section clicked with what you saw while chasing those redefinition errors. Making this article pushed me to go further into how that expansion step behaves, so I really appreciate the feedback and you sharing that debugging story!