Message-ID: <87BC54A997CCD01198930020AFF6011C270ED3@mail.rkk.cz>
From: "Holejsovsky, Pavel" <PHolejs AT rkk DOT cz>
To: djgpp AT delorie DOT com
Subject: RE: Djgpp and Asm
Date: Wed, 9 Jul 1997 20:58:47 +0200
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On Monday, July 07, 1997 8:50 PM, john Conner [SMTP:Fuckyou AT nowhere DOT com]
wrote:
> Matthew Mastracci wrote:
> > 
> > On Sun, 6 Jul 1997, john Conner wrote:
> > 
> > > asm("leal _RAM,%ebp");    /* RAM is a c pointer */
> > >
> > > It crashes every time. I get a gpf or stack fault.
> > > It works fine if I use esi,edi,ect. Any help?
> > 

<snip>

> nope, I'm trying to move RAM(yes its defined) to %ebp. Basicly what im
> trying to do is pass a pointer into an obj asm module that uses %ebp
for
> one of its functions.

But %ebp is used internally as a stack frame pointer, compiler-generated
code references all local variables using %ebp (unless you compiled with
-fomit-frame-pointer, then %esp is used for this purpose and %ebp is
another free register to use for optimizations performed by compiler).
So you MUST preserve %ebp, e.g.

__asm__("pushl %ebp; leal _RAM, %ebp; ....; popl %ebp")

I couldn't try it here and hope that pushing %ebp won't confuse the
compiler even more. If it will, then try to save %ebp into GLOBAL (not
local!) variable..

Pavel

BTW: I'd rather send this answer to you personnaly, but I'm really
unsure if fuckyou AT nowhere DOT com is your real SMTP address or just antispam
;-)