How to find the size of a variable without using sizeof() in C++?

Question

How to find the size of a variable without using sizeof() in C++?

Answer 1

Make an array of that type, get the addresses of two adjacent elements, cast them to integer, and subtract.  But generally that's runtime, not compile time.

Answer 2

You don't actually have to make an array.  You can make a pointer to the object, and do the same thing.  Since you're only interested in the pointer arithmetic, you don't even need a real object. Something like this could work:

int a;

obj b;

obj *c = &b;

a = (int)&obj[1] - (int)&obj[0];