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From: tneff@bfmny0.UU.NET (Tom Neff)
Newsgroups: comp.lang.c
Subject: Re: effect of free()
Message-ID: <14636@bfmny0.UU.NET>
Date: 8 Sep 89 13:45:02 GMT
References: <319@cubmol.BIO.COLUMBIA.EDU> <3756@buengc.BU.EDU> <1989Aug17.005548.745@twwells.com> <16022@vail.ICO.ISC.COM> <248@seti.inria.fr> <1010@m3.mfci.UUCP> <10973@smoke.BRL.MIL>
Reply-To: tneff@bfmny0.UU.NET (Tom Neff)
Organization: ^
Lines: 20

In article <10973@smoke.BRL.MIL> gwyn@brl.arpa (Doug Gwyn) writes:
>In article <1010@m3.mfci.UUCP> karzes@mfci.UUCP (Tom Karzes) writes:
>>Nonsense.  There are no indirect or indexed references in the code above,
>>hence no opportunities for invalid address traps.  Period.
>
>Loading an unmapped address descriptor into an address register may
>cause an exception on some reasonable architectures.  Exclamation point.

For this to be true, NULL itself would have to be a "mapped address
descriptor" on those "reasonable architectures," or else you couldn't
even do the compare *before* the free() call.  But if NULL is a mapped
address descriptor, it beats me how you're going to trap dereferences.

I would like to hear one real world example of an architecture where it
can be illegal to compare the VALUE of a pointer variable to 0 after
passing the CONTENTS of the variable to some OS routine.  Also whether
there's a C compiler for that architecture. :-)
-- 
Annex Canada now!  We need the room,	\)	Tom Neff
    and who's going to stop us.		(\	tneff@bfmny0.UU.NET