Fun stuff with \?

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This comes up in an internal discussion about MAX_PATH limit. People do mention that the core file services supports syntax like [\\?\](file://\\?\) for path longer than MAX_PATH. The caveat is that file name with [\\?\](file://\\?\) 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>md "\\?\c:\temp\bar."

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.

c:\Temp\md bar

C:\Temp>dir *bar*
 Volume in drive C has no label.
 Volume Serial Number is B0F1-CCDC

 Directory of C:\Temp

02/18/2004  04:08 AM    <DIR>          bar
02/18/2004  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>dir/s/b 12346.txt
C:\Temp\bar\12346.txt
C:\Temp\bar.\12346.txt

C:\Temp>del /s 12346.txt
Deleted file - C:\Temp\bar\12346.txt

C:\Temp>echo foo > "\\?\c:\Temp\bar.\12347.txt"

C:\Temp>dir/s/b 12347.txt
File Not Found

C:\Temp>type "\\?\c:\Temp\bar.\12347.txt"
foo