Yeah, that's unportable. Although I'm not aware of any system where it doesn't work. For the record, regarding 0 in pointer context the C standard has this to

Yeah, that's unportable. Although I'm not aware of any system where it doesn't work. For the record, regarding 0 in pointer context the C standard has this to say: An integral constant expression with the value 0, or such an expression cast to type void * , is called a null pointer constant. If a null pointer constant is assigned to or compared for equality to a pointer, the constant is converted to a pointer of that type. Such a pointer, called a null pointer, is guaranteed to compare unequal to a pointer to any object or function. -- C89/C90 section 3.2.2.3 Pointers The standard then goes on to say that NULL is a macro that's guaranteed to expand to a null pointer constant.