On 8 April 2010 05:01, ranjith kumar <ranjithproxy@xxxxxxxxx> wrote:
>
> 1) What is the size of an an empty class? On my machine it is showing 1
>
Assuming you mean in C++...
struct Empty {};
Different objects of the same type must have different addresses, so
to allow for arrays, sizeof(Empty) must be > 0.
Empty a[2];
a != a+1 <=> (Empty*)((char*)a + sizeof(Empty))
There is, however, an "empty base class" optimization that the
compiler will try to perform.
struct D : Empty {};
You will probably find that sizeof(D) == sizeof(Empty), rather than
sizeof(D) == 2*sizeof(Empty).
But remember that, for a given type, different object <=> different
address applies to empty base classes too:
struct D2 : D, Empty {};
Because D2 contains 2 sub-objects of type Empty (one a base of D2, one
a base of D), sizeof(D2) >= 2*sizeof(Empty) >= 2.
~ Scott McMurray
