Analyzing ReactOS's code

I will only cite the following piece of code for dessert:

    #define SWAP(a,b,c)  c = a;\
                         a = b;\
                         a = c

http://www.viva64.com/en/a/0076/

>>30

or am I wrong about casting a pointer to a class T to an array of sizeof(T) chars? It always works with structs in C, but classes have some meta information that you aren't supposed to see as a programmer. Would stuff like the vtable pointer get copied over using that approach? I'm not sure.