Under VC++ 6.0, the __FILE__ macro always gets the full file path returned; under VC++ 7.x it typically does not.
To get the VC++ 6.0 behaviour under VC++ 7.x and 8.0, use the /FC (Full Path of Source Code File in Diagnostics) compiler command line option. (link valid as of 11/8/04).

 

(Thanks to Jason Shirk from the VC++ team)