On Wed, Mar 6, 2019 at 10:18 AM Nathan Sidwell <nathan@acm.org> wrote:
Yes, a BMI is required for a header import.  Textually including the
header import's original header file is not equivalent.

It won't be required for the scan stage will it? If it is, there is a bootstrapping problem because there is no good way to figure out which order to build the header-unit BMIs in if they import other header-units. I've been assuming that the scan stage will be able to just temporarily mask off the defines and replace them with the correct ones for the header-unit while scanning a file, so that scanning has no generated dependencies.