From: sandmann AT clio DOT rice DOT edu (Charles Sandmann)
Message-Id: <10205192003.AA20761@clio.rice.edu>
Subject: Re: emacs under w2k
To: lauras AT softhome DOT net
Date: Sun, 19 May 2002 15:03:34 -0500 (CDT)
Cc: eliz AT is DOT elta DOT co DOT il (Eli Zaretskii), djgpp-workers AT delorie DOT com
In-Reply-To: <20274828752.20020519211241@softhome.net> from "Laurynas Biveinis" at May 19, 2002 09:12:41 PM
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> > the lcall is a fairly small (it's in sbrk16.asm) and does the following:
> 
> Is there any way I could use gdb in that code or should I use other
> means to see where it fails?

I don't know of a way to debug the 16-bit PM code called from DJGPP.

My debugging of these things was typically done under OS/2 - which did
an excellent job of printing out everything if a failure happened.
Since I haven't had a working OS/2 system in about 7 or 8 years ...

> > 3) resets the base of cs and ds selectors (note: ds alias's base is not
> >    changed until several hundred instructions later, so there is a 
> >    short term inconsistency - which might cause problems - any exception
> >    at this point would probably kill ntvdm).
> 
> You mean this piece?
> 
> 3:
>         movw    $0x0007, %ax                                    /* reset DS alias base */
>         movl    ___djgpp_ds_alias, %ebx
>         movl    ___djgpp_base_address, %edx
>         movw    ___djgpp_base_address+2, %cx
>         int     $0x31

Yes, that's the one.  If we had the ds_alias passed into the 16-bit 
helper, it would be a matter of adding:
	mov	bx, [ds_alias]
	mov	ax, 0x0007
	int 0x31
Since the base is already loaded into cx:dx.  We could use a register
like bp or dx also (currently not used in interface).

> Well, it seems like it shouldn't be too hard to move to sbrk16.asm.
> But I think it is better to find out real causes for failures first.

I'll try to write a little test program and see if I can make a simple
example fail under Win2K.  If so, it will be much easier to debug.  If
not, then we know it's something special emacs does.