From: dcasale AT my-deja DOT com
Newsgroups: comp.os.msdos.djgpp
Subject: Re: My program hangs under RHIDE's debugger
Date: Fri, 10 Nov 2000 20:23:54 GMT
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

In article <9003-Fri10Nov2000120410+0200-eliz AT is DOT elta DOT co DOT il>,
  djgpp AT delorie DOT com wrote:
> > From: dcasale AT my-deja DOT com
> > Newsgroups: comp.os.msdos.djgpp
> > Date: Fri, 10 Nov 2000 00:53:36 GMT
> >
> > Guess that means I need to copy my build environment to a separate
> > drive, eh?  ^^;;;
>
> It would be interesting to see if this also explains the time
> slow-down...
>
> > > > > Why did you insert PUSHF and POPF?  They are not needed for
> > > > > __dpmi_int calls; I suggest to remove them.
> > > >
> > > > Because another programmer who was working on this code before
me
> > > > found that with _some_ __dpmi_int int 13h calls, interrupts were
> > > > mysteriously turned off after the call returned.  That _may_ be
the
> > > > reason my system clock is slowing down.
> > >
> > > Something must be turning interrupts back on, or else the keyboard
> > > would stop working as well, and you will have a totally wedged
> > > system.
> >
> > Yeah, I know.  He says that the internal code for INT 21h (which I
also
> > use) checks to see if interrupts are turned off, and turns them
back on
> > if necessary.  But, he says that if a certain error condition occurs
> > during an INT 13h call, the function jumps to a spot in the return
code
> > which _misses_ the opcode to turn interrupts back on.
>
> One possible cause of interupts getting subtly disabled is when you
> run a program under a debugger with CWSDPMI as your host.  In this
> case, any code, including library functions, that uses __dpmi_int to
> call any of the DPMI services hooked by the DJGPP debug interface will
> return with interrupts disabled.  This is because CWSDPMI implements
> the Int 31h not quite as the DPMI spec says (I forget the details).
>
> Note that this can only happen under a debugger, and is usually of
> concern only for programs which disable and enable interrupts.
>
> For the rest of this story, including some discussion, see this
> message (this URL is one long line):
>
>   http://www.delorie.com/djgpp/mail-archives/browse.cgi?p=djgpp-
workers/1999/12/30/02:54:16
>
> You can browse the whole thread "Re: GDB, DOS 6.22, CWSDPMI and
> Interrupts" (posted to djgpp-workers) on DJ's server, if you want to
> know more.
>


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