The argument is that it's just _interface_, which has to be that way for interoperability, so has no "creative content". Code that is actually expressive code

The argument is that it's just _interface_, which has to be that way for interoperability, so has no "creative content". Code that is actually expressive code in a header file (inline functions, or non-constant macros) could readily spoil this. I have no idea whether the output headers contains more than structure definitions, constant macros, and forward function declarations.