https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87846
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> --- The implementation of create_directories worked for the Filesystem TS but I didn't update it to cope with the different C++17 semantics for a trailing slash. The empty filename at the end of the path confused the function into thinking it didn't need to create anything.
