I agree that this is just a fancy assert mechanism. But a lot of people are claiming that printf is the best debugger. Sometimes it't the best one can do. Other times a real debugger is the only efficient way. Many programmers that I respect, and I also, use the debugger as a sanity checker. Whenever I code up a new module and it has passed basic functionality tests I fire up my code in a debugger and do a thorough walk through. I find a good many subtle flaws this way, saving a great deal of time in the intensive testing and later QA cycles. I recommend this as a best practice to any programmer.