http://bugs.winehq.org/show_bug.cgi?id=23355
--- Comment #9 from Chris Parker cparke@parkerfamily.name 2010-09-29 12:52:51 CDT --- I'm not sure where to get wintest.exe or kernel32_test.exe, but the app. I attached is a simple C test apply that exercises this specific API function only by passing the command line argument as the "root" argument to the API and printing out the values upon the function's , including the return value and GetLastError() value if the return value is FALSE. If you call with no command line argument, it passed NULL as the root argument (which according to MS documentation is to return the information for the volume of the current directory).
Regarding X:, yes, I see now what you were saying; only if the current directory for the drive is not the root directory does the trailing backslash seem to be needed. Incidentally, this function works in Windows even for UNC paths also, even if the remote share isn't mapped to any drive letter. However, when the current directory is a UNC share path, a trailing backslash is always needed regardless.