Date: Sun, 17 Oct 1999 17:41:41 -0500 (CDT)
From: Dave Dribin <drib AT enteract DOT com>
To: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
cc: djgpp AT delorie DOT com
Subject: Re: spawnvpe hanging and bash GPF after running non-DJGPP exe
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--- Eli Zaretskii <eliz AT is DOT elta DOT co DOT il> wrote:
> On 17 Oct 1999, Dave Dribin wrote:
> 
> > It runs "prog.exe" correctly, but hangs on exit of the program.
> > 
> > Bash also fails, but in a different way.  On return from "prog.exe",
> > bash gets a general protection fault with this dump:
> > 
> > General Protection Fault at eip=482f3; flags=3046
> > eax=00000300 ebx=00000021 ecx=00000000 edx=00000000 esi=00181780 edi=0016b28c
> > ebp=0016b134 esp=0016b128 cs=a7 ds=af es=b7 fs=bf gs=bf ss=af error=00ec
> > 
> > I looked up 0x482F3 in bash.exe and it is an "int 0x31" insruction.
> 
> These symptoms seem to suggest that the program prog.exe that you
> invoked invalidates the Int 31h entry in the IDT.  For example, it
> could be that it hooks Int 31h, but doesn't unhook it before exiting.
> 
> What is that program?  Is it a protected-mode program that uses some
> DOS extender?  It is highly probable that it has a bug.  Perhaps if
> you tell us what that program is, we could help you find a replacement
> that can be run under Bash (and in the DJGPP environment in general).

I was thinking about writing a program that launches games from a
menu.  This particular game is Callus.  You are correct that it is a
protected-mode program.  This is what it displays at startup:

PMODE/W DOS Extender v1.33
Copyright (C) 1994-1997, Charles Scheffold and Thomas Pytel

Finding a replacement is difficult.  Is there anything the launching
program can do to save and restore Int 31h?  Or is it likely the
program trashed other important stuff as well?

Thanx!

-Dave