From my experience working on a commercial game engine, my guess is that almost anyone working on a huge C++ code base (e.g. a game engine, browser, OS or the l

From my experience working on a commercial game engine, my guess is that almost anyone working on a huge C++ code base (e.g. a game engine, browser, OS or the like) would rank compilation speed as the #1 issue they would like to see addressed. Modules seem like the best candidate to improve this issue, primarily by limiting the scope of how much needs to be recompiled whenever a change is made. So I think it's a feature that is worth quite a lot of compiler-writer pain to get shipped, seeing as how many man-years it could save. That said, I don't really see why this would be all that tricky for compilers to implement compared to other recent additions in modern C++ - do you have any particular reason to think it would be? (other than apparently some communication issues within the body making the spec as per the linked article)