What does a leading "\??\" on a windows path mean?

Question

When using GetModuleFileNameEx to query the image path of a running process, some processes have an image path that starts with "\??\". For example, while most processes start "C:\WINDOWS", some processes start "\??\C:\WINDOWS".

What does the leading \??\ mean on a windows path?

Answer 1

It's a Unicode extended-length pathname - see Naming Files, Paths, and Namespaces in MSDN (the "Maximum Path Length Limitation" section).

(By the way, do you mean \\?\ rather than \??\?)