I think that's a given. Generated code isn't even... generated by including a header. (I'm assuming you're thinking of templates.) You need use site "caching"

I think that's a given. Generated code isn't even... generated by including a header. (I'm assuming you're thinking of templates.) You need use site "caching" to be able to reuse template parsing beyond the parsing step. I think linkers do a little bit of this, but that's after compile time. Even just caching the parse will probably be a little win in the case of complex C++ headers (esp. system headers with lots of platform defines, etc), but it's unlikely to be a panacea for compile times. I think the interesting part is what kind of tech can be built on top of the "headers are isolated" parts of the C++ modules proposal. The compiler are people are nothing if not inventive!