If what you say is true, then you have to either put up with the warnings, compile at a level that doesn't have the warnings, or figure out a hack around them - I don't like any of those options.
I'm not as dogmatic as some others are in the thread. I just think it's a good idea to be warned when a variable is unused, enough that I'll mark my very few that might be #ifdef'ed out. If you're using a compiler that doesn't let you mark variables as such... well that sucks. You do what you can.
