When passing "foo\bar" to boost::filesystem::path constructor, it is accepted when compiled with MSVC, but is refused when compiled with mingw-gcc (v3.4.2). "foo/bar" argument is accepted with both compilers. Test-case: #include <boost/filesystem/path.hpp> #include <iostream> using namespace boost::filesystem; using namespace std; int main(int argc, char *argv[]) { path::default_name_check(native); try { path p1("foo/bar"); cerr << "ok - constructed from 'foo/bar'" << endl; } catch (std::exception &e) { cerr << e.what() << endl; } try { path p1("foo\\bar"); cerr << "ok - constructed from 'foo\\bar'" << endl; } catch (std::exception &e) { cerr << e.what() << endl; } return 0; } Compiled with: g++ -I c:\boostcvs\include\boost-1_33 -L c:\boostcvs\lib test-path.cpp -o test-path -lboost_filesystem-mgw-d Tested against: Boost 1.32 release, CVS HEAD Is it a bug in FS library, or I'm doing something wrong? One would expect native paths be accepted by path with native namechecker, and I can't see any mingw/msvc-specific code in FS library, which could explain why it works with one compiler, but not with other compiler... Alo