What C compilers have non-zero null pointers?

[M.Marking]

jc at minya.UUCP (John Chambers) writes:

) After following a bit of debate in another newsgroup concerning 
) dereferencing null pointers, I've become curious as to how various
) C compilers actually represent null pointers.  I've never actually
) seen a C compiler that uses anything other than all 0 bits for
) a null pointer, but some people insist that this is quite common

My recollection is that there are "funny" NULLs on those machines
that use 1s-complement arithmetic (Univac 1100, some CDC stuff)
because sometimes you can conveniently generate exceptions on
"minus zero". But it's been a few years...