Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!cs.utexas.edu!usc!srhqla!nrcvax!kosman!kosman.uucp!kevin
From: kevin@kosman.uucp (Kevin O'Gorman)
Newsgroups: comp.sys.ibm.pc
Subject: Beginner's question: interrupt handlers in MS-C 5.1.
Message-ID: <1127@kosman.UUCP>
Date: 2 Feb 90 07:43:24 GMT
Sender: kevin@kosman.UUCP
Organization: K.O.'s Manor - Vital Computer Systems, Oxnard, CA 93035
Lines: 29

I feel both annoyed and stupid.  Maybe someone can help.

I've been programming in C for a while, but this is my first crack at
an Intel machine, let alone MSDOS.

I'm working at a new place and I would like to look at least better than
incompetent, so I don't want to mess up something that should be obvious.

This is my first task: take an interrupt handler from a TSR, writtem in
MASM, and rewrite it in C.  This is a 286 running DOS as an imbedded
controller.

I found _dos_setvect() and friends to do the INT 25H for me, but I read
in the manual:
	interrupt far *handler;
and
	If _handler_ is a C function, it must have been previously de-
	clared with the interrupt attribute. Otherwise, you must make
	sure that the function satisfies the requirements for an
	interrupt-handling routine."

Sounds good, but I have been completely unable to find any reference on
the "interrupt attribute" or on the requirements for ...

Anybody out there ever write one of these things?  What they talking
about, anyway???  About all I can think of is that the attribute may
set up DX for me on entry to the function.  The MASM examples all have
code to do that that assumes a tiny model, it seems, and that's not what
I have here.  Is that it???