Re: Why can't I hook INT 21h???

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#1097

From: Frank Hoffmann
Date: Fri, 21 Aug 1992 14:18

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rmathews@zeus.calpoly.edu (Bob Mathews) writes:

>Charlie_Hutchins@mindlink.bc.ca (Charlie Hutchins) writes:
>>Okay, maybe someone could help me here.  I am trying to write a TSR
>>that hooks interrupt 21h but whenever I try and hook that vector I
>>get an invalid command.com error and my system crashes.  I am using
>>TC++ 3.0 ....
>[code deleted]

>The turbo c interrupt function automatically saves all cpu registers.
>The return values from DOS are getting clobbered.  Code like this
>absolutely needs to be written in assembly.  You need to have complete
>control of what's happening to the machine.

>swehtam bob

Same does MSC 5/6. You must write in ASM as well or add additional ASM-Code
to restore the regs and the stack-ptr.

frank
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References: <14340@mindlink.bc.ca> <1992Aug18.034041.195326@zeus.calpoly.edu>

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From: Frank Hoffmann <fh.pad@sni.de>
Subject: Re: Why can't I hook INT 21h???
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References: <14340@mindlink.bc.ca> <1992Aug18.034041.195326@zeus.calpoly.edu>
Date: Fri, 21 Aug 1992 14:18:28 GMT
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