https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81797
--- Comment #12 from Francois-Xavier Coudert <fxcoudert at gcc dot gnu.org> --- (In reply to Francois-Xavier Coudert from comment #10) > The only thing I can think of is that maybe, just maybe, it's due to > filesystem timestamp granularity? My 10.13 system is running on APFS > filesystem, which has 1 ns granularity (smaller than 1 s for HFS+). Some potential confirmation of this: compiling with the 10.12 Xcode 8 on the 10.13 machine with APFS leads to the same error. Another difference between HFS+ and APFS is file ordering: “Calling readdir(2) on a directory in APFS returns filenames in hash order, whereas HFS+ returns filenames in lexicographical order.”