CODEWITHSUNDEEP
c++
Kam
Kam

Reputation: 6008

how are offsets determined when implicitly up-casting?

#include <iostream>
using namespace std;

struct Left
{
   char i = 'k';
};

struct Right
{
   int a = 99;
};

struct Bottom : Left, Right
{};

int main()
{
    Bottom b;

    Left* l = &b;
    cout << l->i;

    Right* r = &b;
    cout << r->a;

    return 0;    
}
// output
// k99

How did this work?

if the memory layout of Bottom is:

Left
Right
Bottom

Then slicing b (i.e. Bottom) to Left object, should be ok, but how can it work when I slice Bottom to Right object?

Why isn't static casting required in this case?

Upvotes: 1

Views: 37

Answers (1)

David Schwartz
David Schwartz

Reputation: 182761

Since the compiler knows the types of both pointers, it can apply the necessary offset adjustment. If you print out the values of the pointers, you'll see that they're a bit different.

Upvotes: 2

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