I’ve embarked down this same path with GCC 2.7.4 from a … while … back.

Ingo is on the right track.

I’ve always thought that this stuff should have been dealt with by the GCC (in form of pre-cached header files).

So sad that it is a thorny issue to this day (for large scale projects); so glad that this issue is now alive so it can be dealt with once and for all.

I envision some type of *.ho filetype to hold these quasi-compiled headers for the next build iteration.