typecheck code

Hi all, /* * Check at compile time that something is of a particular type. * Always evaluates to 1 so you may use it easily in comparisons. */ #define typecheck(type,x) \ ({ type __dummy; \ typeof(x) __dummy2; \ (void)(&__dummy == &__dummy2); \ 1; \ }) #define typecheck_fn(type,function) \ ({ typeof(type) __tmp = function; \ (void)__tmp; \ }) Can anyone help me, explain the above code typecheck. How does (void)(&__dummy == &__dummy2) evaluates to 1 I appreciate any explain. -- Regards, Sri.