Legit Uses of the offsetof Macro in C / C++

Question

There is this macro offsetof in C/C++ which allows you to get the address offset of a member in a POD structure. For an example from the C FAQ:

struct foo {         


        

Answer 1

One legitimate use of offsetof() is to determine the alignment of a type:

#define ALIGNMENT_OF( t ) offsetof( struct { char x; t test; }, test )

It may be a bit low-level to need the alignment of an object, but in any case I'd consider this a legitimate use.