[fpc-pascal]Modifying cpu registers while in turbo pascal interrupt routine ?

Harald Houppermans houppermans at home.nl
Thu Mar 18 16:26:04 CET 2004

----- Original Message ----- 
From: "Klaus Hartnegg" <klaus at fischer.brain.uni-freiburg.de>
To: <fpc-pascal at lists.freepascal.org>
Sent: Thursday, March 18, 2004 9:02 AM
Subject: Re: [fpc-pascal]Modifying cpu registers while in turbo pascal
interrupt routine ?

> > Turbo pascal 7 has the 'interrupt' directive which can be placed behind
> > procedure name to turn it into a interrupt handler.
> forget it, it's a bug
> it doesn't save all registers (so your program will crash if it uses

Yes I read this somewhere else... It doesn't store the high word of the 32
bit registers like eax, ebx, etc.

So as long as I don't use longint's it should be ok.

> and it doesn't provide a stack (so your programm will crash even it it
> use longint).

Euhm... why will it crash ?

Let me gues... if I call other routines from inside the interrupt routine ?

That seems logical... since call routines requires a stack to be present...
the push stuff on it etc and pop it back.

Euhm it's a little bit weird that it hasn't a stack... are you absolutely
sure about that ?

( Proving it would be best :D )

Anyway is that right ? calling other procedures/functions will make it crash

So as long as no other procedures and functions are called it should work...
or is there still another way to make it crash because it doesnt have a
stack ?

> > The problem is that these parameters are probably passed 'by value'. So
> > these are only copies.
> try trapint.pas from this page:
> http://www.brain.uni-freiburg.de/~klaus/pascal/sources/
> hope this helps,
> Klaus
> -- 
> Klaus Hartnegg, Brain Research Group, University Freiburg,
> Hansa-strasse 9a, D-79104 Freiburg, Germany, hartnegg at uni-freiburg.de
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