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From: guy%gorodish@Sun.COM (Guy Harris)
Newsgroups: comp.lang.c
Subject: Re: Casting NULL?
Message-ID: <12048@sun.uucp>
Date: Sat, 24-Jan-87 04:26:53 EST
Article-I.D.: sun.12048
Posted: Sat Jan 24 04:26:53 1987
Date-Received: Sat, 24-Jan-87 13:46:18 EST
References: <3179@brl-adm.ARPA>
Sender: news@sun.uucp
Reply-To: guy@sun.UUCP (Guy Harris)
Organization: Sun Microsystems, Mountain View
Lines: 17

>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.