https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93244
--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> --- Basically GCC's filesystem lib has two kinds of behaviour, POSIX and Windows. Cygwin is a subset of POSIX, as it works like it in most respects, but I also added support for "//foo" as a root-name, which other POSIX systems don't support. The Windows behaviour is mostly independent, so if it should also support "//foo" as a root-name, that needs to be done separately, as part of the Windows semantics, not the POSIX (or Cygwin-POSIX) semantics.
