Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!caen!kuhub.cc.ukans.edu!markv
From: markv@kuhub.cc.ukans.edu
Newsgroups: comp.sys.amiga.programmer
Subject: Re: Can you use Signal() from an input handler?
Message-ID: <1991May4.193801.30388@kuhub.cc.ukans.edu>
Date: 4 May 91 19:38:01 CDT
References: <2032@ria.ccs.uwo.ca>
Followup-To: comp.sys.amiga.programmer
Organization: University of Kansas Academic Computing Services
Lines: 52

>      I want to send a signal from the handler to the main program using
> Signal(), so that the main program can do some DOS stuff.
>      - The Task pointer (pointing to the main program) and a
>       pre-AllocSignal()-ed signal bitnumber are passed to the handler
>       in it's data area.(The data area isn't used otherwise,in this handler.)
> 
>      So far so good. Using kprintf's to a serial terminal I know things
> are getting passed OK. But el GURU visits as soon as the Signal() function
> is called in the handler.

Signal() is kosher in an interrupt.  The trick is, if your handler is
in C, and if you are in a small data addressing scheme, then your
library base isn't automatically addressable by the handler.  Under
SAS, either:
	-compile the module with the handler with -y
	-use the __saveds keyword (I've had some problems mixing
	 mulitple keywords on functions though) on the function.
        -call geta4(); as the first line of the function.

This is isn't a problem with 32 bit absolute addressing.  Speaking of
near/far, in this example, things wouldn't be a problem if the library
base pointer *itself* was far data, but I cant figure out in SAS the
way to declare pointers with the far keyword to put the pointer
storage itself far, I always get a pointer to a far object.  On DOS I
can do something like this:
(assume Near data model is default):

//	sizeof(foo) = 2
	far  footype   	*foo;	// foo is near ptr located in far data segment

//	sizeof(foo) = 4
	footype far	*foo;   // foo is far ptr located in default DS

//	sizeof(foo) = 4
	far footype far *foo;	// foo is far ptr in far data segment.
//OOPs, too much C++ ;-)

But SAS croaks unless far comes after the type, which means always
modifies the kind of pointer it is, not where it goes.  Granted ANSI
says modifiers must come after the type, but that makes it tough to do
things like this.  DOS compilers bend the rule, since esp. on DOS the
three proceeding situations are quite different, and you may want all
three.
-- 
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Mark Gooderum			Only...		\    Good Cheer !!!
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