Printf as such is an insecure function(char*,...) which doesn't check whether ... has valid contents. Double check if your field definition matches the printf() parameters, i.e. if you have printf("%d %d %d",x,y /* ,z */); it may compile OK but break on run, as well as will printf("%f",(short)(x)) where %f asks for 4 bytes and x is just 2. With %s value missing results are usually worse because it reads some random value what happens to be next in memory and treats it as pointer to some other memory location, possibly very far, quite possibly not present in system (like 4th gigabyte of RAM...).