Casting NULL?

[Guy Harris]

>I have a question about pointers: I just recently read
>a C text where whenever NULL was passed as a parameter
>it was casted to the proper type.

All praise to the author of the text for that!

>He claimed that this is required because pointers to different types of
>objects may not be the same size.

That isn't the half of it.  NULL is *!*!NOT*!*!* a pointer, in most
implementations of C, it's just 0.  (There are good reasons for
this.)  There are plenty of implementations where 0 and "(char *)0"
are not the same size.

Furthermore, there is no guarantee whatsoever that an integral
constant 0 and and a null pointer of some type have the same bit
pattern.