Printf as such is an insecure function(char*,...) which doesn't check whether ... has valid contents.
Oh boy, should we bloat the '51 with code that try to protect us agains ourselves. The very difference between (small) embedded and so called "Windows applications programming" is that you are supposed to know what you are doing. I have seen enough embedded code from Windows programmers to puke for the rest of my life and the excuse always is "why did the software not tell me". Darn it, if we are to go that way (it is not our responsibility) we may as well ask for a large salary reduction, since that would reduce what we produce to novice level.

Erik