Will this trick work in C?

Question

I want to add a field to a structure in C. So for example I have the following structure.

struct A
{
 some_type x;
 some_type y;
}

I declare a

Answer 1

Yes, it would work. A a will be the first member in the struct

This is how some people simulated OO inheritance in C

You may use

  &b->a

instead of the cast. And probably do an ASSERT like

 ASSERT (&b->a == b)

to be warned when you accidentally destroyed this semantic