Re: STiNG, CAB, and Multitasking (strikes back) (fwd)

[Peter Rottengatter <perot@pallas.amp.uni-hannover.de>]

On Wed, 11 Mar 1998, Konrad Kokoszkiewicz wrote:

> The question isn't whether or not MiNT uses XBRA - it does. We already

So far, it has only been stated that MiNT provides XBRA headers, that's
hardly "using" XBRA. "Using" it would mean to exploit XBRA's benefits.


> know that. The question is, what parts of the system are appropriate for
> third-party software to be changing? The privilege-violation vector is
> unquestionably the property of the operating system, and not an application.

This is the Unix point of view. Under Unix this is true. However, TOS is
not Unix, and despite your (impressive - I'm not turning it down in any
way) efforts, TOS plus MiNT isn't Unix either. You've done a great job
of getting closer to it, but it's not possible to get there, given the
wealth of existing software that *uses* exception handlers all over the
place.

Such hardlinership is seriously threatening general compatibility of MiNT,
and this cannot do the small Atari world any good. Maybe it's merely
because some people cannot accept that MiNT is *not* the whole Atari
world. STinG has *not* been written *for* MiNT. STinG has been written
such that any system extension that does things in a sensible manner
will work with it. Unlinking exception handlers is not sensible behaviour.
A software installs an exception handler for a very good reason. By
unlinking it, MiNT cripples it. You can say the software is not appro-
priate for MiNT, but that won't help the user who wants to run both, but
can't, because of some hardliners, that insist on something "belonging" to
the system exclusively, which is in no way historically (nor by Atari) 
justified. Remember, it's not Unix.

I wonder if you'd change your mind once some important (for you) piece of
software is affected. Maybe NVDI. The Behnes are good friends of Andreas
Kromke (MagiC). If they'd decide to use an exception handler that in some
similar way doesn't work with MiNT, they won't care, since Andreas' MagiC
does not cause trouble here, neither does any single-TOS. MiNT does not
play such a big role in Germany, which is the main market for the Behnes.


> TOS already provides several legal, documented calls for getting in and out
> of Supervisor mode. As such, STiNG's method can only be viewed as a dirty
> hack. Konrad has also already shown that STiNG's method is slower than a
> more legitimate approach, in CPU cycles.

He's shown nothing. I haven't given you the information based on which
anything could be deduced here. So how could anybody have shown anything ?
STinG's problem at that position is that it works from an interrupt. So 
any call to GEMDOS is entirely out of question. The code does not know
if it was called in Super mode or not, but it's the former case (Super
mode) when the "transition" must be particularly fast. It had not been a
problem if Motorola had not made reading the CPU status system byte a
priviledged instruction.


> So, you have a dirty hack that not
> only causes problems, but also wastes CPU time.

The latter is wrong, as I just explained. The former, well, sure it's so
easy to blame compatibility problems to the other program, saying it uses
dirty hacks :-( Fact is this method does not violate any specification or
guideline by Atari. Fact is this method works with all versions of single-
TOS, all versions of MagiC, MagiCMac on Macintosh, MagiC-PC on PC, AFAIK
all other emulators on both Mac and PCs. Fact is, a programming practice
does not become illegal just because you do not like it ! Atari never has
forbidden linking handlers into exception vectors, after all there is a
BIOS call to simplify (encourage) it !

Another point : STinG is an OS extension just like MiNT is. So STinG has
every right, even by your own (questionable) point of view, to use 
exception handlers.


> so far in this discussion shows only that MiNT observes all accepted Atari
> programming standards, and that STiNG is broken. Can we please move on now?

I consider it precisely the other way round. MiNT chops of other program's
exception handlers, which is a very questionable thing to do. I cannot see
which standard I'd broken by installing an exception handler.

I do not see how we could come to any sensible conclusion, at least as
long as hardliners dominate the discussion. So it seems there is only one
thing I can do : Bow out here, and call MiNT broken by standards set by
Atari whenever anybody complains that STinG run before MiNT does not work.


Cheers  Peter

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   Peter Rottengatter       perot@pallas.amp.uni-hannover.de
                            http://www.stud.uni-hannover.de/~perot
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