int always 32 bits on all platforms?

[AJ]

"BCS" <none at anon.com> wrote in message 
news:a6268ffbadb8cc20772570e4f0 at news.digitalmars.com...
> Hello aJ,
>
>> How can/does D guarantee that "int" will always be 32 bits on all
>> platforms? Does this mean that D won't work on some platforms?
>
>
> D is not built for 8 or 16 bit systems. However 32 bit math can be done on 
> a 16 bit CPU, it's just slow. In the other direction, 32 bit math (and 16 
> and 8 bit) can be done on a 64 bit CPU so that's not a problem.

I wasn't thinking about math issues, but rather struct field 
alignment/portability, and platform alignment requirements for basic types, 
issues. I'm guessing that it is all worked out by the compiler, so that 
makes the development of a compiler more difficult, if so, but how much more 
difficult? A simple example or description of how this is done would really 
be great. (BTW, this is definitely an area where I would approve of more 
language implementation complexity for the great strides in programming 
efficiency (and fun!) it gives).