Crate rucc_debug 

DWARF 5 generation.

Design: spec/11-asm-objects-debug.md. Layer rank 10, 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 M8.

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.

Two things already waiting

Options::prefix_map in rucc-session holds a debug list, which is what -fdebug-prefix-map= and -ffile-prefix-map= put there. Every path this crate writes into a compilation unit, a line table or a file table has to go through PrefixMap::apply on the way, because that is the whole reason a distribution passes those flags and because a build is only reproducible if all of the paths in it are rewritten rather than most. The driver takes the flags today and nothing reads that list, which is honest only while there is no DWARF at all.

Options::compress is the other, and it is what -gz put there. Every debug section this crate hands to the object writer has to be compressed the way that field says, which for Compress::ZlibGnu also means the section is named .zdebug_info rather than .debug_info and carries a ZLIB tag and a length instead of an Elf64_Chdr. Compressing the sections is worth more than anything else a distribution shipping debug symbols passes, so a build that asked for it and got a file twice the size it expected has a real complaint.

Constants

MILESTONE

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