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From: gwyn@smoke.brl.mil (Doug Gwyn)
Newsgroups: comp.std.c
Subject: Re: Why no arithmetic on void *
Message-ID: <14948@smoke.brl.mil>
Date: 23 Jan 91 23:27:53 GMT
References: <1238@dkunix9.dk.oracle.com>
Organization: U.S. Army Ballistic Research Laboratory, APG, MD.
Lines: 17

In article <1238@dkunix9.dk.oracle.com> bengsig@dk.oracle.com (Bjorn Engsig) writes:
>Could someone please explain if arithmetic on void * (with the same semantics
>as on char *) was discussed when ANSI C was made, and why it was not included.

The main purpose of void and void* was to provide additional compile-time
safety checking.  This would be largely defeated if pointer arithmetic
had been allowed on void*.  Note that such arithmetic would have had to
have been specially defined for that one type, since it does not fit the
pointer-arithmetic model given for additive operators.  (If it HAD been
made consistent, we would have had to declare that sizeof(void)==0 and
then void* arithmetic would not have had the same behavior as char*
arithmetic anyway.  So it would have had to violate the model, which is
obviously extremely undesirable.)

Note also that there is absolutely no need for such a wart, since you
can perform the desired pointer arithmetic after casting the void* to
char*.