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In article <4l33mf$7pr@solutions.solon.com> msz@sirius.astrouw.edu.pl
(Michal Szymanski) writes:

|> There is a discussion of (void *) and pointer casting going on this list.
|> K&R "Ansi C" book says that conversion: (type *) -> (void *) -> (type *)
|> is guaranteed to yield the same pointer. This (and the discussion on the
|> list) suggests that another chain: (void *) -> (type *) -> (void *)
|> might result in some change of the original pointer. In other words
|> I would guess that casting a void pointer to a pointer to a type requiring
|> special memory allignment might involve adjusting it to a proper value.
|> Is this true? I played with such conversions on Sun Sparcstation
|> (which surely requires proper allignment of data with sizeof > 1),
|> using both Sun compiler v. 2.0.1 and Gnu 2.6.3, but never observed
|> such an automatic adjustment? Odd pointers casted to (e.g.) double
|> result in Bus Error when referenced. And they show the same odd value
|> when printed as long values.

|> So I wonder whether this adjustment is just (nowhere-implemented) possibility 
|> or some real thing?

The adjustment is certainly legal, although I don't know of an
implementation that does it.  More of a problem occurs, however, on
implementations where `type*' contains less bits than `void*'.
Obviously, in such cases, some information will be lost.  (Typically,
this will `look like' the compiler has adjusted the pointer downward.
In fact, it is just a case of throwing away the bits it doesn't have
room for.)
-- 
James Kanze           (+33) 88 14 49 00          email: kanze@gabi-soft.fr
GABI Software, Sarl., 8 rue des Francs Bourgeois, 67000 Strasbourg, France
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