size of a datatype without using sizeof

Question

I have a data type, say X, and I want to know its size without declaring a variable or pointer of that type and of course without using sizeof oper

Answer 1

A lot of these answers are assuming you know what your structure will look like. I believe this interview question is intended to ask you to think outside the box. I was looking for the answer but didn't find any solutions I liked here. I will make a better assumption saying

struct foo {
  int a;
  banana b;
  char c;
  ...
};

By creating foo[2], I will now have 2 consecutive foo objects in memory. So...

foo[2] buffer = new foo[2];
foo a = buffer[0];
foo b = buffer[1];

return (&b-&a);

Assuming did my pointer arithmetic correctly, this should be the ticket - and its portable! Unfortunately things like padding, compiler settings, etc.. would all play a part too

Thoughts?