X-Authentication-Warning:	delorie.com: mailnull set sender to djgpp-workers-bounces using -f
From:	sandmann AT clio DOT rice DOT edu (Charles Sandmann)
Message-Id:	<10205162012.AA13835@clio.rice.edu>
Subject:	Re: Malloc/free DJGPP code
To:	djgpp-workers AT delorie DOT com
Date:	Thu, 16 May 2002 15:12:15 -0500 (CDT)
In-Reply-To:	<9464-Thu16May2002223923+0300-eliz@is.elta.co.il> from "Eli Zaretskii" at May 16, 2002 10:39:23 PM
X-Mailer:	ELM [version 2.5 PL2]
Mime-Version:	1.0
Reply-To:	djgpp-workers AT delorie DOT com
Errors-To:	nobody AT delorie DOT com
X-Mailing-List:	djgpp-workers AT delorie DOT com
X-Unsubscribes-To:	listserv AT delorie DOT com

> > From: sandmann AT clio DOT rice DOT edu
> > Date: Thu, 16 May 2002 14:14:16 -0500 (CDT)
> > 
> > So negative arguments only work for the unixy sbrk,
> > or standard sbrk for increments which don't step over a block 
> > boundary.
> 
> You mean, they _could_ work, right?  Because I don't think we do that
> now, even when the Unixy sbrk bit is set.

I should say negative sbrk() does something non-harmful if you are
careful, and the memory can be used by future sbrk()s with positive
values.  This twisted feature is actually used by Quake (my fault) - 
so you could lock all the memory into a single block, then sbrk()
negative some back to give libc some room for malloc to sbrk().
Required to get enough memory on 16-Mb Win95 systems and lock it 
in place in memory so virtual DMA worked.

- Raw text -