This comes up in an internal discussion about MAX_PATH limit. People do mention that the core file services supports syntax like \\?\ for path longer than MAX_PATH. The caveat is that file name with \\?\ is not canonicalized by the OS. This can lead to many funny behavior. One of our senior developer writes the following example to illustrate this problem.
C:\Temp>dir *bar* Volume in drive C has no label. Volume Serial Number is B0F1-CCDC
Directory of C:\Temp
02/18/2004 04:06 AM <DIR> bar. 0 File(s) 0 bytes 1 Dir(s) 6,810,882,048 bytes free
C:\Temp>rd bar.The system cannot find the file specified.
02/18/2004 04:08 AM <DIR> bar02/18/2004 04:06 AM <DIR> bar. 0 File(s) 0 bytes 2 Dir(s) 6,810,882,048 bytes free
C:\Temp>echo foo > bar.\12346.txt
C:\Temp>del /s 12346.txtDeleted file - C:\Temp\bar\12346.txt
C:\Temp>echo foo > "\\?\c:\Temp\bar.\12347.txt"
C:\Temp>dir/s/b 12347.txtFile Not Found