Sender: nate AT cartsys DOT com
Message-ID: <374730AF.831BEA33@cartsys.com>
Date: Sat, 22 May 1999 15:33:19 -0700
From: Nate Eldredge <nate AT cartsys DOT com>
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To: djgpp AT delorie DOT com
Subject: Re: problem with extended inline asm
References: <Pine DOT SUN DOT 3 DOT 91 DOT 990518135146 DOT 24330X-100000 AT is> <3743B4E7 DOT 12663C12 AT go DOT ro>
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Reply-To: djgpp AT delorie DOT com

Radu Georgescu aka skoola wrote:
> 
> > > the static and the automatic variables are located in memory one next to
> > > another, if they are declared so
> >
> > This is simply not true.  Static variables go to the data section
> > while automatic variables are on the stack.  So they could be
> > megabytes apart.  You can easily verify that by taking an address of a
> > variable and printing it.
> 
> you didn't understand what i'm talking about. you have to know the address of
> one static variable and then you can address the others using the following
> model:
> static short a,b;
> asm("
> mov 2+%0,%%ax
> "
> :
> :"g"(a));
> and you get
> 
> mov b,ax
> 
> if both a and b are automatic variables, you may also do this stuff but there
> should be -2+%0 instead 2+%0 ,IMHO

NO. This may work now but you CANNOT depend on it.  The compiler is at
liberty to place variables wherever it wants.  There is absolutely
nothing requiring it to put variables declared together adjacent to each
other.

This is even more so for auto variables.  One or both may be put in
registers or even optimized entirely out of existence.

If you want to know where a variable lives, you have to ask the
compiler.  Plain and simple.
-- 

Nate Eldredge
nate AT cartsys DOT com