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Message-ID: <3C79833E.7282AF8D@yahoo.com>
Date: Sun, 24 Feb 2002 19:20:14 -0500
From: CBFalconer <cbfalconer AT yahoo DOT com>
Organization: Ched Research
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To: djgpp-workers AT delorie DOT com
Subject: Re: Malloc/free DJGPP code
References: <10202201713 DOT AA23034 AT clio DOT rice DOT edu> <3C7919F2 DOT 96FFA97D AT yahoo DOT com> <200202241740 DOT g1OHeOd19302 AT envy DOT delorie DOT com>
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Reply-To: djgpp-workers AT delorie DOT com

DJ Delorie wrote:
> 
> > This could all be cured by a semi-portable implementation of, say,
> > "fakesbrk" which will return a repeatable set of addresses under
> > the same circumstances.  It might actually malloc a large block
> > which contains those addresses to be faked.  But how can it ensure
> > that a certain range is available to any degree of certainty, or
> > even of probability?
> 
> Put a huge uninitialized static array in your program and use it for
> sbrk.  It will always be in the same virtual address.

Do you see any problem with the following?  I was surprised to
read that sbrk returns -1 for failure.  This way the test program
can fool with it by making small silly allocations to foul the
sequence.  I'll worry about going backwards later.

#include "fakesbrk.h"

enum {FAKESIZE = 1234567};

char fakearea[FAKESIZE];

/* 1------------------1 */

/* we can fool with this to generate test cases */
void *fakesbrk(int delta)
{
static char *unused = fakearea;
char        *next, *p;

   next = unused + delta;
   if ((unsigned) next > FAKESIZE) return (void *)-1;
   else {
      p = unused;
      unused = next;
      return (void *)p;
   }
} /* fakesbrk */

-- 
Chuck F (cbfalconer AT yahoo DOT com) (cbfalconer AT XXXXworldnet DOT att DOT net)
   Available for consulting/temporary embedded and systems.
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