Date:	Thu, 07 Nov 1996 08:45:28 +0000
From:	Bill Currie <billc AT blackmagic DOT tait DOT co DOT nz>
Subject:	Re: Question
To:	Draximus AT fab DOT net
Cc:	djgpp AT delorie DOT com
Reply-to:	billc AT blackmagic DOT tait DOT co DOT nz
Message-id:	<3281A1A8.A11@blackmagic.tait.co.nz>
Organization:	Tait Electronics NZ
MIME-version:	1.0
References:	<327FF0BE DOT 27B8 AT fab DOT net>

Eric Christopherson wrote:
> 
> There is a program, called A.
> Program A has a variable V.
> Program A shells out and runs Program B, passing a pointer to V (in
> hex).
> Is it at all possible for B to read V (if A and B are compiled with
> DJGPP)?
> I don't know much about MSDOS memory management, and this is something
> that has bugged me for awhile.
> --
> +-- -  -        .      .x
> |  Eric Christopherson  |
> x.      .        -  - --+


If your not running under dpmi 1.0 (very rare) this can be done easily.

What ou want to do is also pass the selector of the variable (_my_ds()
in go32.h I beleive)
and use the _far* functions in sys/farptr.h to access it.

dpmi 1.0 is supposed to give each program it's own address space (as I
understand it) 
and so B could not access anything in A unless you used shared memory
(see the dpmi 1.0 spec)

Bill
-- 
Leave others their otherness.

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