How to find the size of a variable without using sizeof

Question

Let us assume I have declared the variable \'i\' of certain datatype (might be int, char, float or double) ...

NOTE: Simply consider that \'i\' is

Answer 1

It's been ages since I wrote any C code and I was never good at it, but this looks about right:

int i = 1;
size_t size = (char*)(&i+1)-(char*)(&i);
printf("%zi\n", size);

I'm sure someone can tell me plenty of reasons why this is wrong, but it prints a reasonable value for me.