Structure pointer question

[Doug Gwyn]

In article <389 at proxftl.UUCP> bill at proxftl.UUCP (T. William Wells) writes:
>The C standard should make that explicit, don't you think?

It's been known for many years that the logic of C requires that
structure pointers all "smell the same" in a certain sense (for
example, in the context of sizeof).  However, they definitely do
NOT have to have the same representation.  For example, in a C
interpreter they could contain tag information that could be used to
distinguish between them (presumably to detect usage errors).