Agreed. Good use of PImpl when you have large external header-only libraries is also generally recommended to keep the dependency graph nicer. Also from what I

Agreed. Good use of PImpl when you have large external header-only libraries is also generally recommended to keep the dependency graph nicer. Also from what I've seen, large header-only codebases tend to be external and thus generally don't change that much, so if you can limit your own internal dependency tree ccache can still save you.