Date: Thu, 12 May 94 08:41:01 JST
From: Stephen Turnbull <turnbull AT shako DOT sk DOT tsukuba DOT ac DOT jp>
To: djgpp AT sun DOT soe DOT clarkson DOT edu
Subject: [support AT qdeck DOT com: Re: malloc under DV/X]

This is what support AT qdeck says about David Ronis's malloc question.
Seems a bit strange to me, as I would assume that DJGPP manages its
own heap by getting (XMS, EMS, VCPI, DPMI) memory.  But maybe what he
meant is that this is a problem with the EMS (XMS, VCPI, DPMI)
standard.
    I'm going to follow-up to QOS support, but for the interim,
thought I'd post what I have.  (QOS doesn't support its users as well
as GO32 does, there is no "int QOS")

From: support AT qdeck DOT com (Technical Support)
Subject: Re: malloc under DV/X

Stephen Turnbull Writes:

> According to: ronis AT onsager DOT chem DOT mcgill DOT ca (David Ronis)
> 
>    I use djgpp under Desqview/X.  For the most part, I use it when I
>    need to access large arrays.  Thinks work correctly, but I've
>    noticed that malloc allocates system memory irreversibly; for
>    example, free doesn't seem to return the memory to the system
> 
> This is verified also for GhostScript 2.9.5 beta, I believe for other
> versions of GhostScript but I haven't tried it.  I don't know for sure
> that GS frees buffers after erasing an image (GS code is huge), but I
> think it does, and Peter Deutsch told me that he doesn't think there
> are such memory leaks; other systems don't report them.
> 
>    (DV/X) until the program exits, or if I have a large local array in
>    a function, this memory is not returned to the system when the
>    program exits.
>
> I haven't seen this.
> 
>    Is this correct? If so, can it be overridden?

	Yes it is correct, but it is not the fault of DESQview or the
compiler.  This is a problem with DOSes heap allocation - it will not change
no matter what you try.  However, I belive that the memory is recoverable by
the application which freed it - though I haven't tested this myself.


... but the memory is returned to the system once the program exits.

> Have you tried using DJGPP from DOS?  Under DPMI?  I will try these
> later, but haven't got time right now.

	I use DJGPP frrom DOS on a regular basis with DPMI.  If you're
asking if this will solve the problem - no.  The problem is that this memory
cannot actually be freed while the program is running.  DOS will only return
the memory to the system once the program has terminated.
-- 
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        Quarterdeck Office Systems - Internet Support - Marc Newman
 Tech Questions : support AT qdeck DOT com  :  DVX v2.0 ORDER hotline: (800)256-4987
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