Hi, Following the discussion in the "New errors on Cygwin" thread, I have now switched Boost.Filesystem to treat Cygwin as a POSIX platform. The change is now in develop and is planned to be released in Boost 1.91. As noted in that thread, this is a breaking change for Cygwin users, unless they were already using a patched Boost.Filesystem to a similar effect. Among the things that are visible to users are: * The path::value_type type has changed from wchar_t to char. As on other POSIX platforms, wide character paths will be converted to the narrow character encoding using the locale set by path::imbue. Note that since Cygwin is running on top of Windows, it will also perform character code conversion internally. It is important that locale in the Cygwin environment is configured correctly. * Path syntax now follows POSIX conventions, Windows-specific paths (e.g. UNC paths, drive names and path prefixes) are not supported. * Certain Windows-specific parts of the API will become inaccessible. Since reparse points are a Windows-only feature, file_type::reparse_file will not be reported for files. Reparse point handling is dependent on Cygwin runtime behavior. * Cygwin has its own implementation of symlinks that is incompatible with native Windows symlinks. Boost.Filesystem will now create and operate on Cygwin symlinks. * Error codes reported by Boost.Filesystem will now use POSIX errno values. There may be other differences that I forgot to mention. There is no fallback option, other than patching Boost.Filesystem or staying on an older version, and this is intentional. Making this choice user-configurable opens up too many possibilities for inconsistencies and ODR issues, especially given that Boost.Filesystem is a compiled library. It would also complicate maintenance.