The GetModuleFileName() takes a buffer and size of buffer as input; however its return value can only tell us how many characters is has copied, and if the size is not enough (ERROR_INSUFFICIENT_BUFFER).
How do I determine the real required buffer size to hold entire file name for GetModuleFileName()?
Most people use MAX_PATH but I remember the path can exceed that (260 by default definition)...
(The trick of using zero as size of buffer does not work for this API - I've already tried before)
Implement some reasonable strategy for growing the buffer like start with MAX_PATH, then make each successive size 1,5 times (or 2 times for less iterations) bigger then the previous one. Iterate until the function succeeds.