Checked on Linux and Mac - doesn't work correctly. mkdtemp() returns a different name every time it's called, and GetUserCfgDir() is called in three places, meaning we end up with three different tmp directories (which on quick examination didn't all get cleaned up at end).

I'd suggest changing it so that GetUserCfgDir() caches its result and returns the cached version on subsequent calls. Running out the door so don't have time to try this myself right now...