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From: meissner@dg_rtp.UUCP (Michael Meissner)
Newsgroups: comp.lang.c
Subject: Re: How big is a (??? *)
Message-ID: <2108@dg_rtp.UUCP>
Date: Sun, 14-Jun-87 09:59:51 EDT
Article-I.D.: dg_rtp.2108
Posted: Sun Jun 14 09:59:51 1987
Date-Received: Sat, 20-Jun-87 20:23:18 EDT
References: <737@edge.UUCP> <790@mcgill-vision.UUCP> <1243@epimass.EPI.COM>
Reply-To: meissner@dg_rtp.UUCP (Michael Meissner)
Organization: Data General (Languages @ Research Triangle Park, NC.)
Lines: 22

In article <1243@epimass.EPI.COM> jbuck@epimass.EPI.COM (Joe Buck) writes:
>	/* sombody else from edge.UUCP */
> >This should work, but not because of the reason you quoted.  K&R says,
> >and presumably ANSI follows them in saying, that a pointer to any
> >object can be cast to a pointer to any smaller object and back without
> >change.  Since a char is the smallest object available, any pointer can
> >be cast to (char *) and back without change.
> 
> Ah, but what about pointers to functions?  There are models for the
> 80x86 architecture (boy, I'm glad I don't have to program that thing)
> where pointers to data are 16 bits and pointers to functions are 32
> bits.  In cases like this, a char pointer isn't wide enough.

ANSI has a void * which is guaranteed to be large enough to point to any
data object (pre-ANSI could use char *).  However, ANSI explicitly says
that in standard conforming programs, you cannot convert from a pointer
to a function to a pointer to a data object (and vica versa).  It is left
as a common extension to be able to do so.
-- 
	Michael Meissner, Data General	Uucp: ...mcnc!rti!dg_rtp!meissner

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