+/// Converts a host OS style path to a unicode safe unix style.
+/// On Windows, this is achieved by using the short form of the path,
+/// which can be safely passed to standard I/O functions expecting narrow
+/// char paths even when the path contains non-ascii chars.
+/// As the short form is only available for existing files, if the file is
+/// to be accessed for writing, \param how should be set to CREATE.
+/// \p p and the return value are encoded in utf8.
+std::string safe_internal_path(std::string const & p, file_access how = EXISTING);
+