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From: evans@ditsyda.oz (Bruce Evans)
Newsgroups: comp.lang.c
Subject: Re: effect of free()
Message-ID: <2196@ditsyda.oz>
Date: 9 Sep 89 20:13:51 GMT
References: <319@cubmol.BIO.COLUMBIA.EDU> <3756@buengc.BU.EDU> <10971@smoke.BRL.MIL> <2054@munnari.oz.au> <247@ssp1.idca.tds.philips.nl> <10982@smoke.BRL.MIL>
Reply-To: evans@ditsyda.oz (Bruce Evans)
Organization: CSIRO DIT Sydney, Australia
Lines: 18

In article <10982@smoke.BRL.MIL> gwyn@brl.arpa (Doug Gwyn) writes:
>In article <247@ssp1.idca.tds.philips.nl> dolf@idca.tds.PHILIPS.nl (Dolf Grunbauer) writes:
>>What about the case when ptr is already in a register
>>(i.e. definition of ptr: register char *ptr) ? Will there be an address trap
>>right after the free as some address register now holds an invalid address ?
>
>No, provided that you don't try to copy the now-defunct address into some
>other variable or to use it in any other way.  Storing a valid address in

	register char *ptr;
	...
	free(ptr);

The compiler will have difficulty maintaining the register across the function
call. It might have to forbid pointers in registers, or they might not fit.
A loss either way.
-- 
Bruce Evans		evans@ditsyda.oz.au