Crate rucc_pp 

Macro expansion, conditionals, include resolution, and the header cache.

Design: spec/05-preprocessor.md. Layer rank 5, see spec/18-package-layout.md.

Status

Not implemented. This crate exists from the first commit so that the layer rank it holds is real and cargo xtask layers has something to check. The work lands in M1.

Every crate in the workspace is published, and publishing implies a promise. This one is tier 3: its Rust API is explicitly unstable and will change without a major version bump. Depend on the rucc binary’s behaviour, not on this.

Constants

MILESTONE

The milestone in spec/17-milestones.md that fills this crate in.