[boost] filesystem 1.61.0 and cygwin: Windows assumed, posix expected

Hi, On cygwin, the following program #include <iostream> #include <boost/filesystem.hpp> int main() { auto p = boost::filesystem::path{"foo"}; p /= "bar"; std::cout << p.string() << '\n'; return 0; } outputs: foo\bar but cygwin is a posix system and I expect: foo/bar I read in the doc that "User-defined BOOST_POSIX_API and BOOST_WINDOWS_API macros are no longer supported." So how can I have posix support on cygwin? Thanks, Frédéric