: Creates the
resolves to, with
attributes copied from directory existing_p.
The set of attributes
copied is operating system dependent.
fails because p
resolves to an existing directory,
no error is reported.
Otherwise on failure an error is reported.
For POSIX-based operating systems, the
attributes are those copied by native API stat(existing_p.c_str(), &attributes_stat)
followed by mkdir(p.c_str(), attributes_stat.st_mode).
Windows-based operating systems, the attributes are those copied by native
API CreateDirectoryExW(existing_p.c_str(), p.c_str(), 0).
— end note