Just so you know, local non-static variables (i.e. ones that are allocated from the stack) are never initialised implicitly and unless explicitly initialised will start with whatever value that happened to be in that memory location at the time of their creation. This behavior is in the C standard and not in any way specific to gcc. When compiling with gcc you should always have warnings enabled (-Wall option) as then it will more often than not tell you about these kinds of problems in your code.