What type for subtracting 2 size_t's?

Question

Which type in C should be used to represent the difference between two objects\' sizes?

As size_t is unsigned, something like

size_t dif         


        

Answer 1

When I am really worried about overflow issues like that (especially when working in modular arithmetic where "negative" values wrap somewhere other than ~0) I just split it into two cases:

if (a > b) {
    size_t diff = a - b;
} else {
    size_t diff = b - a;
    // code here subtracts diff rather than adds it, etc.
}