[mtzet]

That's a bit misleading though. The problem with header files is that they tend to get (textually) included in lots of compilation units, and hence rebuilt a lot of times. I did an experiment on a codebase at work where turning on unity builds -- so effectively everything is a single c++ file -- resulted in a 2x speedup in real time, and a 12x reduction in 'user' time.

Of course, such approaches lead to slower hot rebuilds. There's trade-offs worthy of a book. But the point is that C++ is only massively parallel by adding a lot of extra work.

This problem could be overcome by reducing the complexity of header files, but that's generally difficult if template-types are used. In general, the solution is to write code that's closer to C than C++ in the header files. In particular using opaque pointers to hide data.

We're actually seeing a very similiar problem in the linked article. The chief problem is monomorphization (~templates) and the solution is to use boxing (~data hiding via opaque pointers).