Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!rutgers!cmcl2!adm!news
From: CDCKAB%EMUVM1.BITNET@cunyvm.cuny.edu ( Karl Brendel)
Newsgroups: comp.lang.pascal
Subject: Re: SHRINK BEFORE RUNNING A CHILD PROCESS
Message-ID: <27232@adm.brl.mil>
Date: 18 Jun 91 17:02:45 GMT
Sender: news@adm.brl.mil
Lines: 42

In article <913@baby.and.nl> berto@and.nl (Bert van Oortmarssen)
  wrote:

>In article <11940@j.cc.purdue.edu> zhou@brazil.psych.purdue.edu
> (Albert Q.Zhou) writes:
>>In Turbo Pascal, the dynamic memory to be used in a program has to be
>>specified during the compilation by $M. However, when you run a child
>>program with exec, you can not use any part of the memory already
>>allocated for the heap even if it is free. Is it a way to get around this?

[...deleted...]

       if (maxavail<minimumavail) then EXIT;

[...deleted...]

         GetMem(SaveFreelist, FreelistSize);

[...deleted...]

                           { how many paragraphs are in use ?? }
      PargrInUse := Seg(HeapPtr^) - PreFixSeg;

[...deleted to end...]

Perhaps I'm wrong, but it seems to me that the test MaxAvail <
MinimumAvail (which perhaps we should call MinimumRequired) does not
guarantee that the shell will be provided the specified memory,
since there is no guarantee that the block referenced by MaxAvail
lies at the top of the heap. A better scheme might be to
GetMem(SaveFreeList,...) _first_, then compare MinimumAvail to sum
of the size of the block between HeapPtr^ and FreePtr^ plus the size
of the free list.

Cheers--                        --Karl

+====================================================================+
| Karl Brendel                           Centers for Disease Control |
| Internet: CDCKAB@EMUVM1.BITNET         Epidemiology Program Office |
| Bitnet: CDCKAB@EMUVM1                  Atlanta GA  30333       USA |
|                        Home of Epi Info 5.0                        |
+====================================================================+