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From:	Hans-Bernhard Broeker <broeker AT physik DOT rwth-aachen DOT de>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Interrupt handler question
Date:	12 Apr 2004 11:49:46 GMT
Organization:	Aachen University of Technology (RWTH)
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Joel <jbs30000 AT aol DOT com> wrote:

> Now, I hook a real mode interrupt and my routine is called.  Now say,
> at a certain point, I want the old handler called.  I could try this:
> _go32_set_real_mode_interrupt_vector(Interrupt Number, &OldInt);
> Set the dpmi reg struct as needed
> _dpmi_int(Interrupt Number, &r);

Depends on where you do this from.  Doing this from inside the
"NewInt" handler function itself is almost certainly a no-no.
Interrupts, or more particularly their handling routines, aren't
generally reentrant.

Generally speaking there's a limit as to what you can do in this area
using C code.  You'll have to revert to assembly sooner or later, at
least for the "outer layers", i.e. the routines actually registered as
interrupt handlers.  C code can be called from there if you're
careful.


-- 
Hans-Bernhard Broeker (broeker AT physik DOT rwth-aachen DOT de)
Even if all the snow were burnt, ashes would remain.

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