Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!munnari.oz.au!uniwa!vaxa!a_dent
From: a_dent@vaxa.uwa.oz
Newsgroups: comp.sys.mac.programmer
Subject: Re: THINK Pascal saving A4 for Objects in CODE resource
Message-ID: <1651.261273d0@vaxa.uwa.oz>
Date: 29 Mar 90 12:45:04 GMT
References: <1645.2610e886@vaxa.uwa.oz> <2377@husc6.harvard.edu>
Organization: University of Western Australia
Lines: 28

In article <2377@husc6.harvard.edu>, siegel@endor.harvard.edu (Rich Siegel) writes:
> In article <1645.2610e886@vaxa.uwa.oz> a_dent@vaxa.uwa.oz (ME) writes:
>>I am working on a Quickmail bridge which requires a CODE resource.
>>The THINK documentation says you can't use globals in CODE resources but it
>>would be LOTS easier to write if I could use Object Pascal.  Am I correct in
>>assuming that Object Pascal can be used if you can save and restore A4?
> 
> 	Right now, you can't write code resources in Object Pascal, because
> you need a jump table to support the method dispatches, and no mechanism is
> supported for the jump table at this time.
> 
WOW - thanks for the speed of response.  I'm still not entirely convinced that
I can't hack a way round this.  On page 131 of the manual it states that 
"If your driver uses Object Pascal, you must check the Multi-segment option..."

So, your driver glue somehow can fake having a jump table (that's also why
multiple segments work, for those who were wondering).  Now, in this Quickmail
environment, I CAN have other resources providing their numbering corresponds
to a base address from the CODE resource.  

Is there any way I can actually compile a DRIVER and then hack it?  How secret
is your driver glue and particularly the bits setting up the jump table?  I'm
prepared to dissassemble code if I have to but don't want to write a commercial
product that violates any patents or stuff. 

Andy Dent                     A.D. Software phone 09 249 2719
Mac & VAX programmer          94 Bermuda Dve, Ballajura
a_dent@vaxa.uwa.oz            Western Australia  6066