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From: richard@aiai.ed.ac.uk (Richard Tobin)
Newsgroups: comp.unix.questions
Subject: Re: sbrk(2) question
Message-ID: <4319@skye.ed.ac.uk>
Date: 15 Mar 91 11:59:25 GMT
References: <1991Mar8.180132.12025@Think.COM> <4296@skye.ed.ac.uk> <6582@auspex.auspex.com> <4312@skye.ed.ac.uk> <2045@necisa.ho.necisa.oz.au>
Reply-To: richard@aiai.UUCP (Richard Tobin)
Organization: AIAI, University of Edinburgh, Scotland
Lines: 23

In article <2045@necisa.ho.necisa.oz.au> boyd@necisa.ho.necisa.oz.au (Boyd Roberts) writes:
>|        sbrk(100000);
>|        printf("hello world\n");
>|        sbrk(-100000);

>Well, I thought everybody new that sbrk(2) and malloc(3) just
>don't mix.

There is no reason for sbrk() and malloc() to "not mix" provided you're
careful not to free memory you didn't allocate.  On the other hand,
there's not usually a good reason to not just use malloc().

>Odds on printf(3) calls malloc and gets some memory
>whose address is > sbrk(0) + 100000*.

Yes, this is what happens.  Malloc() uses sbrk() to get some memory,
and the user's sbrk() frees it.

-- Richard
-- 
Richard Tobin,                       JANET: R.Tobin@uk.ac.ed             
AI Applications Institute,           ARPA:  R.Tobin%uk.ac.ed@nsfnet-relay.ac.uk
Edinburgh University.                UUCP:  ...!ukc!ed.ac.uk!R.Tobin