Can a pointer (address) ever be negative?

Question

I have a function that I would like to be able to return special values for failure and uninitialized (it returns a pointer on success).

Currently i

Answer 1

It's generally a bad design to try to multiplex special values onto a return value... you're trying to do too much with a single value. It would be cleaner to return your "success pointer" via argument, rather than the return value. That leaves lots of non-conflicting space in the return value for all of the conditions you want to describe:

int SomeFunction(SomeType **p)
{
    *p = NULL;
    if (/* check for uninitialized ... */)
        return UNINITIALIZED;
    if (/* check for failure ... */)
        return FAILURE;

    *p = yourValue;
    return SUCCESS;
}

You should also do typical argument checking (ensure that 'p' isn't NULL).