[Brian_K_White]

headers perform the same job for all code, not just code that's in some library.

Frankly your description of what you just called easy sounds terrible and pointlessly extra, indirection that doesn't pay for itself in the form of some overwhelming huge win somewhere else. It's easy only if the alternative was getting it by fax or something.

[saghm]

Having to make an entire separate file to mark something as public rather than just having a keyword in the language sounds to me "terrible and pointlessly extra". It's not like you can't just put all your public stuff in it's own file in Rust rather than putting private stuff in it as well; empirically though, people don't do this because it's just not worth the effort.

[nine_k]

Think about closed-source software that has to export a low-level programmatic interface. You may not believe it, but it's still widespread.