[Bug libstdc++/81797] gcc 7.1.0 fails to build on macOS 10.13 (High Sierra):

[fxcoudert at gcc dot gnu.org]

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.”