Is there a big difference between a function returning -1 and ~0?

Question

Consider the two simple functions:

int return0Comp(){
    return (~0);
}

int returnNeg1(){
    return -1;
}

I know that on a twos-complement system, ~0==-1, but on the off-chance that a system isn't using that (does that even happen?*), will these two functions be returning different values?

What language is this? Most have very specific semantics for what `~` does. — Thilo, Oct 28 '15 at 06:12
I use a c++ compiler, usually. But I wouldn't think they treat zero's compliment differently? — galois, Oct 28 '15 at 06:36

score 2 · Accepted Answer · answered Oct 28 '15 at 07:18

The standard says [expr.unary.op.10]

The operand of ~ shall have integral or unscoped enumeration type; the result is the one’s complement of its operand.

I read this that ~ always just inverts all the bits, so the interpretation of the result should indeed depend on the representation used.

Is there a big difference between a function returning -1 and ~0?

1 Answers1