https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77985
--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> --- So I just fixed the bug here, but yes, I don't know about the design decision. I suppose CWD was decided to be useless in case of an absolute path to the file. I don't think the debug info preserves -I paths in any standard way, so what's exactly the reason you consider CWD not redundant here? [we could rewrite the file-name to relative to CWD]
