Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!lll-winken!sun-barr!texsun!texbell!vector!attctc!chasm
From: chasm@attctc.Dallas.TX.US (Charles Marslett)
Newsgroups: comp.lang.c
Subject: Re: effect of free()
Summary: A real, usable example that answers the question, or go on to the next
	 Please!
Message-ID: <9386@attctc.Dallas.TX.US>
Date: 16 Sep 89 23:25:23 GMT
References: <319@cubmol.BIO.COLUMBIA.EDU> <3756@buengc.BU.EDU> <11063@smoke.BRL.MIL>
Organization: The Unix(R) Connection, Dallas, Texas
Lines: 32

In article <11063@smoke.BRL.MIL>, gwyn@smoke.BRL.MIL (Doug Gwyn) writes:
> I've now seen at least four such examples posted in this newsgroup.
[With reference to architectures that fail to support access to pointers
after the memory pointed to is deallocated.]

I have seen two inaccurate examples (in that there do not exist, and probably
could not exist) of such -- assuming very poor quality code generation for
Intel 80x86 processors.

Neither could survive an environment with interrupts (and therefore, could
not exist on any OS I know of for the Intel chips).

A third example, for a fictitous processor, does indeed have the same
characteristic, and it may in fact be able to support C.  Without any
details, I would not assert it to be possible, however, and I would be very
inclined to disbelieve any assertion that both a standard version of C (one
that would accept anything like the language we know today) and Unix (or
Multics) could coexist on the machine.

I missed the fourth example.  Sorry :^(.

Would the next poster who wishes to address the issue either provide some
reasonable archtecture (say a tagged one with no registers, only memory, for
example -- I cannot think of another possibility, yet) where comparision of
an invalid pointer to 0 can generate a trap, OR provide evidence that such
a failure would keep the machine from handling the C language.

I would like to lear a bit from the discussion, but it seems to have
degenerated to a "does so, does not, DOES SO, DOES NOT, ...".

This is much like the religous wars between the Mac and IBM folk, or the Atari
and Amiga folk -- lots of useless noise, so far.