petroffheroj

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Greetings.

This message has been cross-posted to a significant amount of conferences,
so, first of all, apologies if this is an off-topic _here_! I deliberately
allowed myself to do that, since getting info on DOS or getting help from DOS
fellas has become a hard task nowadays, and I wanted as much response as
possible. If you think the letter is an off-topic here, don't kill me , but
instead suggest some conferences (missing in the list), that you think are
more proper. Thank you for understanding.

Following is the message I have sent to Tenberry (ex-Rational Systems).
However, I decided to post to Usenet because I didn't get any replies from
Tenberry for about a week, and since they suggested to post to Usenet, well,
I am now Tenberry-blessed, right?

The message is self-explanatory, so I won't prepend it with much foreword.
I'd be very thankful to get any _worth_ and _qualified_ opinions from you on
the problem, with some practical experience, and it's my dream if some of you
conducted the experiment described below, to reproduce the bug, and responded
about results. It _would_ be heaven if someone could tell me the reason of
the problem, but that's too daring

Thank you and good bye!

P.S. The source address is not present since I'd like the discussion to stay
in public. If you want to mail directly for some reason, request the address
here.

--------------------------------------------------------------------------
From: "PetroffHeroj"
To: 4gsupport@tenberry.com,4gwhelp@tenberry.com
Date: 2003-10-02

Hello.

This is a report for a bug in DOS4GW.

First of all, the bug is in v1.97, and as I don't have any later versions,
the descriptions of changes made in v2.01 of DOS4G and DOS4GW have been
examined prior to sending this report, and the bug doesn't seem to be fixed
yet. So I suppose the information is still valuable.

The bug was found by accident, it was reproduced on several machines, it was
proven that the bug is in DOS4GW interrupt handling code, because it doesn't
happen with other extenders (tested with Tran's PMODE/W). Sorry, no
disassembly was made to find out the cause of the bug itself, so you'll
probably have to track it down yourself, unless it has been fixed already.

The description of the situation that causes the bug follows:

An int is hooked in the PM chain, then shelling to DOS; if an int occurs
while SP=0 (not a frequent condition, but _completely legal_), DOS4GW
crashes. It wasn't tested with _software generated_ ints, although results
are supposed to be the same. It also wasn't tested _without shelling_ to DOS
(by switching to RM and issuing/catching and int), but it's also supposed to
be the same. Was tested under pure RM and under VCPI service of EMM386. Was
_not_ tested under DPMI in either plain DOS or any DOS emulators. Hence it
might be that the bug can be reproducible in RM or under VCPI only.

The following code will help you to reproduce the bug. The first is the PM
program linked with DOS4GW, compile it under Watcom with:

wcc386 -i=<...>\h bug_pm
wlink f bug_pm libp <...>\lib386;<...>\lib386\dos form os2 le
op stub=wstub.exe

Or to link with PMODE/W for testing purposes:
wlink f bug_pm libp <...>\lib386;<...>\lib386\dos form os2 le
op stub=pmodew.exe

-- bug_pm.c --------------------------------------------------------------

#include <stdio.h>
#include <process.h>
#include <dos.h>

__interrupt __far (*old_vect)();

void __far __interrupt suka() {
__asm in al,61h
__asm xor al,2
__asm out 61h,al
(*old_vect)();
}

void main() {
old_vect=_dos_getvect(8);
_dos_setvect(8,suka);
printf("Errorlevel: %xh\n",system("c:\command.com"));
_dos_setvect(8,old_vect);
}

--------------------------------------------------------------------------

The proggie hooks int 09 in the PM chain and just clicks the PC squeaker,
then calling the old code. Hope you have PC squeaker :^)

The following is a 16-bit asm program that causes the bug to show up when
ran under the former one. It's converted for TASM syntax, can easily be
converted to anything else.

-- cause_rm.asm ----------------------------------------------------------
model tiny
codeseg

entry:
org 100h

xor sp,sp ;that is the key!

again:
mov ax,0E01h
int 10h

xor cx,cx
delay:
in al,0EBh
loop delay

in al,60h
cm al,81h
jne again

int 20h ;sorry, retn-fellows...

end entry
--------------------------------------------------------------------------

Its main purpose is to have SP=0 most of the time and periodically show it's
alive. Since it's almost certain that you have much faster machines than my
486, you can replace "xor cx,cx" and "loop delay" with "mov ecx,<...>" and
"loopd delay" (or prefix "loop" with 67h manually). Basically, it's not a
problem to write a similar program any way you like it.

That's all. It would be very nice if you ****ysed the bug and responded
whether it was reproducible for you or not, since you could have it fixed
already.

Thank you for your attention.

Leonid

Hello, I don't know why you are trying to run down the bug. Here is one
possible solution, there is an open source free to use drop in replacement
for dos4gw called dos32a.zip at:

http://www.programmersheaven.com/zone5/cat19/index.htm

They also have discussion groups etc. which deal with dos extension
applications, maybe your question can be asked there.

Here is a better source for dos32a, at the developer's home page:

http://dos32a.sourceforge.net/html/main.html

petroffheroj

Hello, thank you for your comments.

mc> Hello, I don't know why you are trying to run down the bug.

I am running PC DOS and I use some software linked with DOS4GW or its stub.
One good example is Cubic Player 1.7 - I am not going to move to OpenCP with
whatever extender it uses, because it's inordinately slow compared to CP 1.7
The other is the DOS4GW version of MpxPlay - PMODE/W and the other
DOS-extender that MpxPlay also links with behave incorrectly with shelling
in some cases. Funny, until recently I considered DOS4GW to be the most
stable one (with shelling and at all), because of these quirks of other
extenders, but once again was proven wrong :~(

I am not using this DOS-extender myself in my code and for now not planning
to.

Guess that explains my personal interest in getting the bug fixed and/or
patching the existing DOS4GW executable. And may be there would be people
around the world who'd be interested as well.

mc> Here is one
mc> possible solution, there is an open source free to use drop in replacement
mc> for dos4gw called dos32a.zip at:
mc> http://www.programmersheaven.com/zone5/cat19/index.htm
mc> Here is a better source for dos32a, at the developer's home page:
mc> http://dos32a.sourceforge.net/html/main.html

Thank you very much! By 'drop in' do you mean it can safely replace
dos4gw.exe without any modifications to binaries using DOS4GW?

mc> They also have discussion groups etc. which deal with dos extension
mc> applications, maybe your question can be asked there.

Uhhuh... But that's _not_ on Usenet, is it? Oh, never mind, I'll seek that
myself

Thank you very much for your valuable reply!

Leonid

dr john stockton

JRS: In article <bmhbak$10it$11@news.wplus.net>, seen in
news:comp.os.msdos.misc, PetroffHeroj <forged@address.net> posted at
Tue, 14 Oct 2003 17:21:27 :-

It has not. Do not use terms that you do not understand. Do not multi-
post.

--
© John Stockton, Surrey, UK. ?@merlyn.demon.co.uk Turnpike v4.00 MIME ©
Web <URL:http://www.uwasa.fi/~ts/http/tsfaq.html> -> Timo Salmi: Usenet Q&A.
Web <URL:http://www.merlyn.demon.co.uk/news-use.htm> : about usage of News.
No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News.

petroffheroj

Hello, thank you for your comments.

mc> Hello, I don't know why you are trying to run down the bug.

I am running PC DOS and I use some software linked with DOS4GW or its stub.
One good example is Cubic Player 1.7 - I am not going to move to OpenCP with
whatever extender it uses, because it's inordinately slow compared to CP 1.7
The other is the DOS4GW version of MpxPlay - PMODE/W and the other
DOS-extender that MpxPlay also links with behave incorrectly with shelling
in some cases. Funny, until recently I considered DOS4GW to be the most
stable one (with shelling and at all), because of these quirks of other
extenders, but once again was proven wrong :~(

I am not using this DOS-extender myself in my code and for now not planning
to.

Guess that explains my personal interest in getting the bug fixed and/or
patching the existing DOS4GW executable. And may be there would be people
around the world who'd be interested as well.

mc> Here is one
mc> possible solution, there is an open source free to use drop in replacement
mc> for dos4gw called dos32a.zip at:
mc> http://www.programmersheaven.com/zone5/cat19/index.htm
mc> Here is a better source for dos32a, at the developer's home page:
mc> http://dos32a.sourceforge.net/html/main.html

Thank you very much! By 'drop in' do you mean it can safely replace
dos4gw.exe without any modifications to binaries using DOS4GW?

mc> They also have discussion groups etc. which deal with dos extension
mc> applications, maybe your question can be asked there.

Uhhuh... But that's _not_ on Usenet, is it? Oh, never mind, I'll seek that
myself

Thank you very much for your valuable reply!

Leonid

petroffheroj

Since the conference isn't moderated, I thought it wouldn't be much problem
to do the same thing you did: post an off-topic.

DJS> It has not. Do not use terms that you do not understand. Do not multi-
DJS> post.

No, it has not I had troubles cross-posting this article to the list
above, because of reasons currently unknown to me (the NNTP server accepted
it, but the article didn't appear anywhere), so without further thinking I
put the Newsgroups: field into the body of the message for people's reference
and then sent the article separately to each group.

Do _not_ always presume people to be as ignorant as you are used to, dear
Enchanter named Demon Child I know what cross-posting is.

My only mistake was forgetting to remove 'cross-' from the text when I
re-sent the article. That sure was a cardinal sin, wasn't it?

Thank you very much for your very very helpful post, it was especially to the
point

dr john stockton

JRS: In article <2.7.9.T0JF.HMSSGV@emailacc.com>, seen in
news:comp.os.msdos.misc, PetroffHeroj <forged@address.net> posted at
Wed, 15 Oct 2003 16:10:07 :-


Yes, because it encourages the sloppy use of technical terms.

When you make obvious mistakes, it damages your credibility in what you
intended to say.

--
© John Stockton, Surrey, UK. ?@merlyn.demon.co.uk Turnpike v4.00 MIME ©
Web <URL:http://www.uwasa.fi/~ts/http/tsfaq.html> -> Timo Salmi: Usenet Q&A.
Web <URL:http://www.merlyn.demon.co.uk/news-use.htm> : about usage of News.
No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News.

petroffheroj

DJS> Yes, because it encourages the sloppy use of technical terms.

DJS> When you make obvious mistakes, it damages your credibility in what you
DJS> intended to say.

|D Sorry, father.