Hello Beman, I've used your lib on WIN32 VC7.1 and function's fs::exists behavior was not correct. After applying the following change it works fine: operations_posix_windows.cpp:358 - if(::GetFileAttributesA( ph.string().c_str() ) == 0xFFFFFFFF) + if(::GetFileAttributesA( ph.native_file_string().c_str() ) == 0xFFFFFFFF) I just wonder why test cases are happy in both cases? Best, Oleg Abrosimov.