Newsgroups: comp.os.msdos.djgpp
From: patrick AT spirit DOT gun DOT de (Patrick Fedick)
Subject: Problem combining DJGPP and MASM
Reply-To: patrick AT pfp DOT de
Organization: private
Message-ID: <E95tKA.2I0@spirit.gun.de>
Date: Thu, 24 Apr 1997 20:43:22 GMT
Lines: 60
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Precedence: bulk

Hello,

I'm new to DJGPP, and have some problems combining my assembly functions
with gcc. It seems to be impossible, to use local data in my assembly
modules. If I load a register with the value of a variable, I allways get
the value of the first variable. Example:

   var1	  dd 1
   var2   dd 2
   var3   dd 3
   [...]
   mov eax,var3

If I return to the calling c-function and print the value, it contents
a 3. I don't know why. If I load the eax-register with an absolute
value (like mov eax,3), the c-function prints the right value. 

So I thought there goes something wrong with the data segments, but I
don't use any in my assembly function, and I thought gcc wouldn't use
any either (or am I wrong?).

Here is an example:
--------------------------------------------------------------------------
/* Assembly-Module, called testasm.asm */
.586p
.model flat,c
.code
align 4

var1	dd 1
var2	dd 2

getvar2 proc near public
  mov eax,var2
  ret
getvar2 EndP
END
--------------------------------------------------------------------------
/* C-Module, called test.c */
#include <stdio.h>
unsigned long getvar2 ();

main() {
  printf ("The value is: %u\n",getvar2 () );
}
--------------------------------------------------------------------------
I have compiled the assembly module with MASM 6.11d: ml /c /coff testasm.asm
and the c-module with gcc 2.7.2.1: gcc -o test.exe -O testasm.obj test.c

If I start this program, it returns: "The value is: 1", but it must be "2".
I altered the function to "mov eax,cs:var2", but it still returns "1".

Can anyone explain me this? It would be great, if someone can help me to
fix this problem.

Thanks,

Patrick
-- 
Patrick Fedick     <patrick AT pfp DOT de>