HALF_PTR Windows data type

Question

The VS documentation states

Half the size of a pointer. Use within a structure that contains a pointer and two small fields.

Windows Data Types

What, exactly, is this type and how is it used, if ever?

Answer 1

Note: Anonymous structs are not standard, but MSVC takes them:

union
{
    int * aPointer
    struct
    {
        HALF_PTR lowerBits;
        HALF_PTR upperBits;
    };
} myvar; //You can be assured this union is sizeof(int *)

If you're thinking they're not too terribly useful, you would be right.

Answer 2

I found this article on Intel's site, and it they suggest using it in a context where you have a class with many pointer members, along with a 32-bit offset to get the actual address, to cut down on data bloat of a class. The article specifically talks about the Itanium platform because it uses 64-bit pointers instead of 32-bit, but I assume the problem/solution to the problem would be the same on any system using 64-bit pointers.

So in short, it seems to suggest that it can be used if you, for example, wish to reduce the memory footprint of a class?