I believe the maximum length is 2,147,483,647, but performance could suffer with a value anywhere near that large. You might want to conditionally assign the macro only if the file is smaller than a certain size, or only load part of it (maybe the first 250,000 characters or 2,500 lines).
http://msdn.microsoft.com/en-us/libr...=vs.84%29.aspx
http://msdn.microsoft.com/en-us/libr...=vs.84%29.aspx
http://msdn.microsoft.com/en-us/libr...=vs.84%29.aspx