Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!haven!adm!smoke!gwyn
From: gwyn@smoke.BRL.MIL (Doug Gwyn)
Newsgroups: comp.lang.c
Subject: Re: Varargs problem
Message-ID: <10863@smoke.BRL.MIL>
Date: 28 Aug 89 20:46:29 GMT
References: <4YxPuc200VsnE_B3Jy@andrew.cmu.edu> <1301@levels.sait.edu.au>
Reply-To: gwyn@brl.arpa (Doug Gwyn)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 15

In article <1301@levels.sait.edu.au> MARWK@levels.sait.edu.au writes:
>I am not an expert, but it seems to me that one can always cast a pointer
>to a pointer of another type, ...

No, in fact conversion between object and function pointers is officially
disallowed.  (It surprised me when I first heard about it, but after
pondering the point for a while I decided that was proper.)  Conversion
among object (data) pointers is constrained by the natural alignment
requirements only.

On a true segmented architecture, for example, it might take more bits
to represent a function address than for any data address within a task,
because function pointers would have to include segment identification
while with proper C compiler implementation all the process's data
would be in a single known segment.