Question

Consider the following code:

void Increment(int *arr) {
    arr++;
}

int main() {
    int arr[] = {1,2,3,4,5};
    // arr++  // illegal because its a const pointer
    Increment(arr);   // legal
}

My question is if arr is a const pointer, how come I can send it to a function that doesn’t receive a const pointer?

The code compiles without the warning of discarding const qualifiers.

Answer 1

Don’t get fooled by the pointer. The same holds for plain ints:

const int a = 42;
int b = a; // How can I assign a const int to a non-const int?
int c = 4; // Come to think of it, the literal 4 is a constant too
void foo (int x) { std::cout << x; }
foo(a); // How come I can call foo with a const int?

In summary, const applies to each object individually. A copy of a const object doesn’t need to be const too.