> You have to have an awfully good reason to add 100k lines of code to a project... And I don't think merely shaving 50% off the build time is enough.

In Ingo's post, he points out that the main speedup is coming from the fact that the expansion after the C preprocessor step is a LOT smaller.

That's a lot of decoupling. As someone who had to go rattling over the USB gadget subsystem, I can tell you that running "grep" with "find" was the standard way to find some data structure buried in a file included 8 layers deep. Having those data structures in files actually mentioned by the file you're working on would be a huge cognitive load improvement as well as make tool assistance much more plausible.

Even if this particular patch doesn't land, it lights the path. What types of changes need to be made are now clear. How many changes are required before you see the improvement is now clear. With those, the changes required can be driven down into the maintainers and rolled out incrementally, if desired.